WO2010038204A1

WO2010038204A1 - Zirconium oxide powder

Info

Publication number: WO2010038204A1
Application number: PCT/IB2009/054288
Authority: WO
Inventors: Nabil Nahas; Nicole Rives
Original assignee: Saint-Gobain Centre De Recherches Et D'etudes Europeen
Priority date: 2008-09-30
Filing date: 2009-09-30
Publication date: 2010-04-08
Also published as: JP2012504094A; FR2936515A1; FR2936515B1; EP2344427A1; CN102227390A

Abstract

The invention relates to a powder having a maximum particle size D99,5 of less than 200 μm, a porosity index Ip higher than 2, the porosity index being equal to the ratio Asr/Asg where Asg is the theoretical geometrical specific surface area of the particles of the powder, and Asr is the measurement of the real specific surface area by the BET method, and/or, when all the dimensions of the base particles of the powder are higher than 50 nm, a specific surface area higher than 10m²/g and a total of mesoporous and microporous volumes higher than 0,05 cm³g. More than 20 % of said powder is formed from base particles which are aggregated or not, have dimensions which are all higher than 200 nra, a sphericity index of less than 0.6, and consist of a zirconium oxide and/or a hafnium of formula MOx, M being Zr4+, Hf4+, or a mixture of Zr4+ and Hf4+, and x being a non-zero positive number.

Description

Zirconium oxide powder

Technical area

The invention relates to a method of manufacturing a powder intended in particular to catalyze a chemical reaction or filtration. The invention also relates to a powder manufactured or capable of being manufactured by such a method. More generally, the invention relates to a zirconium and / or hafnium derivative powder, a zirconium and / or hafnium hydrate powder and a zirconium and / or hafnium oxide powder. The invention finally relates to the use of a powder according to the invention in certain applications, in particular catalysis and filtration.

State of the art

Catalysis involves many reactions, in various technical fields, in particular environmental applications, petrochemistry, or fine chemistry. It consists in modifying the speed of a chemical reaction by bringing the reactants of this reaction into contact with a catalyst, for example platinum, which does not appear in the reaction balance. Generally the catalyst is previously deposited on a support, for example in the form of a powder or a body made from such a powder. The powder may also sometimes serve itself as a catalyst. Filtration of fluids also concerns many applications, and in particular the filtration of liquids or gases at high temperatures. For this purpose, the fluids pass through a powder or body made from a powder so that the materials to be filtered are retained by the interstices between the particles, related to their morphology, or in the pores of these particles. In a catalysis application, the particles must have a maximum specific surface in order to increase the contact area between the catalyst and the reactants, whether the particles are used as a catalyst support or as a catalyst themselves. In an application to filtration, a minimal pressure drop is sought during the passage of the fluid to be filtered.

In these applications, the particles can also be subjected to high temperatures or severe thermomechanical stresses. Particles and processes for their manufacture are disclosed in particular in the following documents:

FR 2 662 434 relates to the manufacture of monoclinic zirconia whiskers by hydrothermal synthesis. These whiskers are of micrometric dimensions (approximately 5 μm for the examples cited) and are dense due to a hydrothermal treatment temperature of between 300 ^° C. and 700 ^° C.

EP 0 207 469 relates to the production of crystals of zirconia, sulphate-doped zirconia or zirconium hydrate, optionally doped with sulphate, these crystals being in lamellar form with a thickness of less than 50 nm. The process for producing these crystals comprises heating between 110 ° C. and 350 ^° C. an acidic aqueous solution (pH <2) of a soluble zirconium salt and sulphates, resulting in the production of an oxysulphate of hydrated zirconium (of formula

followed by a calcination at a temperature greater than 600 ^° C. or a desulphatation treatment at a temperature of between 70 and 110 ^° C. It concerns the manufacture of ultrafine particles of monoclinic zirconia in the form of elementary fibers having a diameter of less than 5 nm and agglomerated in the form of "heaps" having a width of between 30 and 200 nm and a length of between 200 nm and 1 μm. The article "Zirconia needles synthesized inside hexagonal swollen liquid crystals" - Chemistry Of Materials, 2004, vol 16, pp 4187- 4192, describes the obtaining of millimeter-sized or even centimeter-sized needles with pores of 20 nm, and made up of smaller needles.

The article "Products of thermal hydrolysis in Zr (SO ₄ )" Zr (OH) ₄ -H ₂ O System "-Journal of the Ceramic Society of Japan, vol 102, No. 9, p 843-846, discusses the manufacturing process that it describes comprises a step of precipitation of an acidic aqueous solution (having a H ⁺ concentration of 0.4 mol.l ^-1 ) of a zirconium salt and sulfates in the presence of Zr (OH) ₄ particles. The present inventors consider that these Zr (OH) ₄ particles are isotropic. The product of the reaction then undergoes a hydrothermal treatment at 160-240 ^° C., which leads to the production of a powder of zirconia particles which the inventors consider as dense.

EP 0 194 191 relates to the manufacture of a stabilized zirconia fine powder. The manufacturing process uses a zirconia hydrate sol consisting of crystallites elemental ZrO ₂ acicular cells of sizes between 1 and 50nm. A calcination treatment at a temperature of between 700 ^° C. and 130 ^° C. followed by sintering at 130 ^° C. leads to stabilized zirconia particles which, according to the present inventors, are isotropic. The article "Highly Ordered Porous Zirconias from Surfactant Controlled Syntheses: Zirconium Oxide Sulfate and Zirconium Oxo Phosphate" - Chemistry Of Materials, 1999, Volume H, pp 227-234, describes the manufacture of a zirconia and sulphate powder. The process for producing this powder comprises a step of precipitation by heating an aqueous acidic solution at 100 ^° C. for 48 hours, According to the inventors, such heating conditions lead to an isotropic morphology of the particles of the precipitate. The precipitate obtained is then calcined at 500 ° C. for 5 hours There is a permanent need for new particles having high specific surface areas and / or new forms There is also a need for particles capable of withstanding high thermal stresses for example the stresses encountered during the combustion of gases at high temperatures.

An object of the present invention is to meet, at least partially, one or more of these needs.

Summary of the invention

processes

According to a first main embodiment, the invention proposes a method of manufacturing a powder of particles, comprising the following successive stages: a) preparation of an acidic mother liquor by mixing at least, or even by a mixture of only :

[1] a polar solvent;

[2] a first reagent, preferably acid-soluble in said solvent, providing Zr ⁴⁺ and / or Hf ⁴⁺ ions; [3] a second reagent providing anionic groups; [4] an additive selected from the group consisting of anionic surfactants; amphoteric surfactants; cationic surfactants, carboxylic acids and their salts; surfactants nonionic compounds chosen from the group of compounds of formula RCO ₂ R 'and R-CONHR' and mixtures thereof, R and R 'being aliphatic, aromatic and / or alkylaromatic carbon chains; and their mixtures; [5] optionally, another nonionic surfactant;

[6] optionally a blowing agent; b) heating the mother liquor so as to precipitate the Zr ⁴⁺ and / or Hf ⁴⁺ ions and the anionic groups in the form of a primary derivative of zirconium and / or hafnium, and optionally drying; c) optionally converting the primary derivative into a secondary derivative of zirconium and / or hafnium by substitution of said anionic groups by other anionic groups, called "substitution anionic groups", and optionally drying; d) optionally, basic hydrolysis of said primary or secondary derivative; e) optionally, calcination (step eι)) or hydrothermal treatment (step e ₂ )) of the primary derivative obtained at the end of step b), the secondary derivative obtained at the end of step c), or the hydrate obtained in end of step d), so as to obtain a zirconium oxide and / or hafnium, and optionally drying.

As will be seen in more detail in the remainder of the description, the inventors have discovered that the addition of the additive leads, in a simple and effective manner, to obtain particles having a morphology or advantageous properties. The optional steps make it possible to transform these particles into other equally useful particles.

Steps a) and b), or even c), make it possible to produce anisotropic and porous or dense particles of a material chosen from zirconium and / or hafnium derivatives, doped or not, preferably chosen from sulphated derivatives of zirconium and / or hafnium doped or not, phosphated derivatives of zirconium and / or hafhium doped or not, carbonates derivatives of zirconium and / or hafnium doped or not, preferably selected from basic zirconium sulfate and / or doped hafnium or not, the basic phosphate of zirconium and / or hafnium doped or not, the basic carbonate of zirconium and / or hafnium doped or not, and mixtures of such particles. Step d) makes it possible to manufacture anisotropic and porous particles made of a material chosen from zirconium and / or hafnium hydrates, doped or otherwise. Such anisotropic and porous particles are not known to the inventors. In one embodiment, for producing a zirconium oxide and / or hafnium oxide powder, the method comprises at least steps a) to e), for producing a powder of hydrates of zirconium and / or hafnium. the method comprises at least steps a) to d), to manufacture a powder of zirconium derivative and / or hafnium, the process comprises at most steps a) to c).

In one embodiment, the method does not include a gelling step. In particular embodiments of the invention, the method may still have one or more of the following features. The polar solvent is water.

The first reagent is chosen from solvent-soluble zirconium and / or hafnium salts, zirconium and / or hafnium alkoxides, acid-soluble zirconium and / or hafnium derivatives in the solvent, preferably chosen from zirconium and / or hafnium oxychlorides, oxides of zirconium and / or hafhium, preferably chosen from zirconium and / or hafnium oxychlorides, and mixtures thereof.

- The concentration of Zr ⁴⁺ ions and / or Hf ⁴⁺ provided by the first reagent in the mother liquor is between 0.01 and 3 mol / liter. This concentration may be greater than 0.1 mol / liter and / or be less than 1.2 mol / liter.

- The second reagent chosen so as to provide SO ₄ ^{2 "} and / or PO ₄ ^3" .

- The concentration of the additive in the mother liquor is between 10 mol / liter and / or be less than 10 ^{^"" 5} mol / liter and 1 mol / liter concentration of the additive may be greater than 10. ^" mol / liter.

- The mother liquor is such that:

the acidity is between 0.6 and 2 mol / l; and

the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in the mother liquor is between 0.1 and 1.2 mol / l; and the molar ratio of anionic groups / (Zr ⁴⁺ and / or Hf ⁴⁺ ) is between 0.3 and 1, in particular between 0.6 and 1; and the concentration of additive in the mother liquor is between 10 ^-3 and 1 (T ¹ mol / l, and in step b),

the heating ramp is between 10 ^-2 and 1 ° C / minute, and

the heating temperature, ie the temperature at the bearing, is between 55 ° C. and 80 ° C., in particular between 55 ° C. and 70 ^° C .; and

the duration of maintenance at the landing is between 15 minutes and 2 hours. Preferably, the mother liquor is adapted so as to lead to a powder comprising more than 20%, more than 50%, more than 80%, more than 90%, or even more than 95% by number of particles of zirconium derivatives. and / or hafnium, optionally doped, at the end of step b) or of step c), into zirconium and / or hafnium hydrates, optionally doped, at the end of the step d), or optionally zirconium and / or hafnium oxides, at the end of step e).

The mother liquor is such that: the acidity is between 1.6 and 3 mol / l; and

the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in the mother liquor is between 0.1 and 1.2 mol / l; and the molar ratio of anionic groups / (Zr ⁴⁺ and / or Hf ⁴⁺ ) is between 0.5 and 1, in particular between 0.5 and 0.8; and

the concentration of additive in the mother liquor is between 10 ^-5 and 10 ^-2 mol / l; and in step b),

- the heating ramp is between 10 ^"° C / minute, and - the heating temperature is between 60 and 80 ° C; and

the duration of maintenance at the stage is between 1 hour and 10 hours. The mother liquor is such that: the acidity is between 1.2 and 3 mol / l; and the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in the mother liquor is between 0.1 and 1.2 mol / l; and the molar ratio of anionic groups / (Zr ⁴⁺ and / or Hf ⁴⁺ ) is between 0.8 and 2.0; and - the additive concentration in the mother liquor is between 10 ^"3 and Io ^'1 mol / 1, and in step b), the heating ramp is between ^10" ° C / minute; and the heating temperature is between 60 ^° C. and 80 ^° C .; and the duration of maintenance at the stage is between 30 minutes and 2 hours.

- The mother liquor is such that:

the acidity is between 1.2 and 3 mol / l; and the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in the mother liquor is between 0.1 and 1.2 mol / l; and the molar ratio of anionic groups / (Zr ⁴⁺ and / or Hf ⁴⁺ ) is between 0.3 and 1; and

the concentration of additive in the mother liquor is between 10 ^-5 and 10 ^-2 mol / l; and, in step b),

the heating ramp is between 10 ^-2 and 1 ° C / minute, and the heating temperature is between 55 ^° C. and 80 ^° C., and

the duration of maintenance at the landing is between 30 minutes and 2 hours.

- The mother liquor is such that:

the acidity is between 1.2 and 3 mol / l; and the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in the mother liquor is between 0.1 and 1.2 mol / l; and the molar ratio of anionic groups / (Zr ⁴⁺ and / or Hf ⁴⁺ ) is between 0.3 and 1; and the additive concentration in the mother liquor is between 10 ^{^"etlO" 1} mol / 1; and in step b), the heating ramp is between 10 ^-2 and 1 ° C / minute, and

the temperature of the bearing and between 60 ^° C. and 80 ^° C. and the duration of maintenance at the stage is between 1 hour and 5 hours,

- The mother liquor is such that: the acidity is between 0.6 to 3 mol / l; and the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in the mother liquor is between

0.1 and 1.2 mol / l; and the molar ratio of anionic groups / (Zr and / or Hr ⁺ ) is between 0.5 and 2; and the concentration of additive in the mother liquor is between 10 ^-2 and

1 mol / l; and in step b), the heating ramp is between 10 ^-2 and 10 ° C./minute, and the heating temperature is between 60 ^° C. and 100 ^° C., and the duration of maintenance at the landing is between 30 minutes and 5 hours - All dimensions of at least 80%, at least 90%, at least 95%, or substantially 100% of the particles obtained at the end of step b ), c), d) or e) are greater than 50 nm.

The mother liquors described above make it possible, after step b), to obtain a primary derivative of zirconium and / or hafnium having a solubility in water at a temperature below 20 ° C. at 10 ^{~ 3} mol / l.

In one embodiment, the parameters of steps a) and b) are determined in order to obtain, at the end of step b), anisotropic primary derivative particles.

Preferably, for producing zirconium oxide and / or hafnium oxide particles having determined dimensions, in particular for producing base particles whose all dimensions are greater than 50 nm, greater than 200 nm, and even greater than 250 nm. zirconium and / or hafnium derivatives of hydrates or derivatives having said dimensions are used as starting particles.

According to a second main embodiment, the invention relates to a process for producing a powder of particles of zirconium hydrates and / or hafnium doped or not and mixtures thereof, comprising a step of basic hydrolysis of a powder of starting particles of a zirconium derivative and / or hafnium doped or not, preferably selected from sulfated derivatives of zirconium and / or hafnium doped or not, phosphatic derivatives of zirconium and / or doped or non-doped hafnium, carbonates derivatives of zirconium and / or hafnium doped or not, preferably selected from basic zirconium sulphate and / or hafnium doped or not, basic phosphate of zirconium and / or hafnium doped or not, the basic carbonate of zirconium and / or hafnium doped or not, and mixtures thereof, or a starting powder in a mixture of such particles, said starting particles being constituted of anisotropic base particles, aggregated or not.

According to the invention, this process therefore comprises a step of hydrolyzing, in a basic medium, starting particles of zirconium derivative and / or hafnium, to transform them into zirconium hydrate and / or hafnium particles. .

The hydrolysis step may in particular be a step d) and, in particular, comprise one or more of the optional characteristics relating to step d). The starting particle powder may in particular be a powder manufactured according to a manufacturing method according to the first main embodiment described above, and in particular be a powder obtained at the end of step b) or from step c).

According to a third main embodiment, the invention relates to a process for producing a doped or non-doped powder of zirconium oxide and / or hafnium oxide particles, preferably ZrO ₂ , doped ZrO ₂ , HfO ₂ , Doped HfO ₂ , comprising a step of calcining a powder of starting particles of a material chosen from doped or non-doped zirconium and / or hafnium derivatives, zirconium hydrates and / or hafnium doped or non-doped, and mixtures thereof, preferably chosen from doped and non-doped sulphated zirconium and / or hafnium derivatives, phosphated zirconium and / or hafnium derivatives which are doped or not, and doped zirconium and / or hafnium carbonate derivatives. or not, the doped or non-doped hafnium and zirconium hydrates, and mixtures thereof, preferably chosen from zirconium and / or doped hafnium basic sulfate, zirconium basic phosphate and / or hafnium doped or not, the basic carbonate of zirconium and / or hafnium whether or not the doped or non-doped hafnium and zirconium hydrates, and mixtures thereof, or of a powder comprising a mixture of such starting particles, said starting particles comprising or even consisting of anisotropic base particles; , aggregated or not, and when they are in a hydrate, the starting particles being further porous.

The calcination step may be a step e _t ) of the first main embodiment and include one or more of the optional features of this step. The anisotropic starting particles may in particular be particles manufactured according to a process according to the first main embodiment, and in particular be derived from steps b), c) or d). According to a fourth main embodiment, the invention also relates to a process for manufacturing a powder of doped or non-doped zirconium oxide and / or hafnium oxide particles and mixtures thereof, comprising a step of hydrothermal treatment of a starting particle powder of a material chosen from doped or non-doped zirconium and / or hafnium derivatives, doped or non-doped hafnium and zirconium hydrates and mixtures thereof, preferably chosen from sulphated zirconium derivatives and / or hafnium doped or not, phosphated derivatives of zirconium and / or hafnium doped or not, doped or unphased doped zirconium and / or hafnium carbonate derivatives, hydrates of zirconium and / or hafnium doped or not and mixtures thereof, preferably chosen from basic sulfate of zirconium and / or hafnium doped or not, the basic phosphate of zirconium and / or hafnium doped or not, the basic carbonate of zirconium and / or hafnium doped or not, hydrated of zirconium and / or hafnium doped or not and mixtures thereof, or a mixture of these particles, said starting particles consisting of anisotropic base particles, aggregated or not, and, when they are in a hydrate the starting particles being furthermore porous.

The hydrothermal treatment step may, in particular, be a step e ₂ ) like that of a method according to the first main embodiment and comprising one or more optional characteristic (s) in step e ₂ ) of the first main embodiment. The starting particles may be manufactured according to a method according to the first main embodiment, and in particular be derived from steps b), c) or d).

In particular embodiments, the starting particle powder comprises only particles of a material selected from

(For the second, third and fourth main embodiments) the doped or non-doped zirconium and / or hafnium derivatives, preferably chosen from doped or non-doped sulphated zirconium and / or hafnium derivatives, phosphated derivatives of zirconium and / or hafnium doped or non-doped, carbonates derivatives of zirconium and / or hafnium doped or not, preferably selected from basic sulfate zirconium and / or hafnium doped or not, basic zirconium phosphate and or doped hafnium or not, the basic carbonate of zirconium and / or hafnium doped or not,

(for the third and fourth main embodiments) doped or non-doped zirconium and / or hafnium hydrates, or a mixture of such particles, said starting particles being composed of anisotropic basic particles, aggregated or not, and, when they are in a hydrate, the starting particles being moreover porous.

In particular, according to this embodiment, said starting particle powder does not comprise zirconium salt and / or hafnium, such as the particles used in the process described in "Products of thermal hydrolysis in Zr (SCUh-Zr ( OH) ₄ -H ₂ O System "- Journal of the Ceramic society of Japan, vol 102, No. 9, p 843-846..

Products The processes described above have made it possible to discover several new particles. Steps a), b) and c) have led to the discovery of anisotropic base particles in a material chosen from doped or non-doped zirconium and / or hafnium derivatives, preferably chosen from sulphated zirconium derivatives and / or or doped hafnium or not, phosphated derivatives of zirconium and / or hafnium doped or not, doped or non-doped hafnium and zirconium carbonate derivatives and mixtures thereof, preferably chosen from basic zirconium sulphate and / or doped hafnium or not, the basic phosphate of zirconium and / or hafnium doped or not, the basic carbonate of zirconium and / or hafnium doped or not and mixtures thereof.

The invention thus also relates to a powder comprising more than 20%, more than 50%, more than 80%, more than 90%, or even more than 95% by number of anisotropic base particles, aggregated or not, in a chosen material. from doped or non-doped zirconium and / or hafnium derivatives, preferably chosen from doped or non-doped sulphated zirconium and / or hafnium derivatives, phosphated derivatives of zirconium and / or hafnium doped or non-doped, doped or non-doped dicarbonated zirconium and / or hafnium carbonate derivatives and mixtures thereof, preferably chosen from the basic sulphate of zirconium and / or hafnium doped or non-doped, the basic phosphate of zirconium and / or doped or non-doped hafnium , the basic carbonate of zirconium and / or hafnium doped or not and mixtures thereof, or a mixture of these particles. In a preferred embodiment, these particles are dense.

In another embodiment, especially when adding a pore-forming agent in step a), these particles are porous.

These base particles are insoluble in water and, preferably, hydrolyzable. Preferably, the material of these base particles is amorphous when not doped. When this material is doped, however, it may present crystals formed from the dopant. In other words, on an X-ray diffraction diagram, the peaks corresponding to the detection of crystals substantially all correspond to crystals containing a dopant.

Steps a), b), optionally c), and d), have led to the discovery of anisotropic and porous base particles, aggregated or not, in a material chosen from zirconium hydrates and / or hafnium, doped or not, and their mixtures.

The invention therefore also relates to a powder comprising, for more than 20%, more than 50%, more than 80%, more than 90%, or even more than 95% by number, anisotropic and porous base particles, aggregated or not , into a zirconium hydrate and / or hafnium, doped or not, or a mixture of such hydrates. The base particles may have identical or different chemical compositions.

Preferably, the material of these particles is amorphous when it is not doped. When this material is doped, however, it may present crystals formed from the dopant.

Steps a), b), optionally c), d) and el) (calcination) and steps a), b), optionally c), d) and e2) (hydrothermal treatment) have led to the discovery of particles of base, anisotropic and porous, aggregated or not, in a material chosen from doped or non-doped zirconium and / or hafnium oxides and their mixtures, preferably ZrO ₂ , doped ZrO _2, doped HfO ₂ , HfO ₂ .

The invention thus also relates to a powder comprising more than 20%, more than 50%, more than 80%, more than 90%, or even more than 95% by number of base particles, anisotropic and porous, aggregated or not, in a material selected from oxides of zirconium and / or hafnium doped or not and mixtures thereof, or a mixture of these particles. Preferably, the material of these particles is crystallized.

The invention also relates to a powder comprising more than 20%, more than 50%, more than 80%, more than 90% or even more than 95% by number of basic particles, anisotropic and dense, aggregated or not, in a material chosen from zirconium and / or hafnium oxides, doped zirconium and / or hafnium oxides and mixtures thereof, the dopant being:

an oxide of an element chosen from yttrium Y, lanthanum La, cerium Ce, scandium Sc, calcium Ca, magnesium Mg and their mixtures, said dopant preferably being in solid solution with the oxide of zirconium and / or hafnium oxide, preferably in a molar amount of less than or equal to 20%. The product according to the invention may in particular be a zirconia doped with yttrium oxide or a zirconia doped with cerium oxide; an aluminum oxide A1, preferably dispersed in zirconium and / or hafnium oxide, preferably in a molar amount of less than or equal to 20%, more preferably less than or equal to 3%;

- and their mixtures.

Preferably, the base particles of said powder are in the form of platelets and / or needles and / or are aggregated in the form of stars and / or lamellae and / or sea urchins and / or hollow spheres. More preferably, the base particles are in the form of platelets and / or are aggregated in the form of lamellae and / or stars, sea urchins and / or hollow spheres. Preferably, the material of these particles is crystallized.

According to one particular embodiment, the invention relates to a particle powder having a maximum size of less than 200 μm, and comprising more than 20%, more than 50%, more than 80%, more than 90%, or even more than 95%. % in number of anisotropic base particles, aggregated or not, and chosen from the group formed by: - the dense or porous base particles into a zirconium and / or hafnium derivative, doped or undoped, insoluble in the water and hydrolyzable, amorphous or containing only crystals that include crystals including a dopant, said zirconium derivative may in particular be selected from basic zirconium sulfate and / or hafnium, basic zirconium phosphate and / or hafnium basic zirconium and / or hafnium carbonate and mixtures thereof; porous base particles of zirconium hydrates and / or hafnium, doped or undoped, amorphous or containing as crystals only crystals including a dopant; porous zirconia ZrO ₂ and / or hafnium oxide HfO ₂ base particles, doped or undoped, and mixtures of these base particles. Preferably, in particular for the porous base particles of a zirconium and / or hafnium derivative, doped or undoped, insoluble in water and hydrolysable, amorphous or containing as crystals only crystals including a dopant and for porous base particles of zirconium hydrates and / or hafnium, doped or undoped, amorphous or containing, for single crystals, only crystals including a dopant and

for the porous zirconia ZrO ₂ and / or hafnium oxide HfO ₂ base particles, doped or undoped, said powder has a porosity index I p greater than 2, preferably greater than 5, preferably greater than 10, or even greater than 20, or even greater than 50. For said porous base particles of zirconium hydrates and / or hafnium, said powder preferably has a porosity index Ip greater than 80, or even greater than 100.

Obtaining a high porosity, and in particular a porosity index Ip greater than 2, requires, for said porous base particles, a zirconium and / or hafnium derivative and with a process according to the invention. the addition in the mother liquor of a pore-forming agent. When the porous base particles are in a zirconium and / or hafnium derivative, doped or not, said powder may have a specific surface area greater than 10 mVg, or even greater than 20 m ² / g, greater than 40 m ² / g, greater than 50 m ² / g, greater than 70 m * / g, greater than 100 mVg and the sum of the mesoporous and microporous volumes of the powder is greater than 0.05 cm ³ / g, or even greater than 0.08 cm ³ / g, or even greater than 0.10 cm ³ / g. When the porous base particles are in a zirconium hydrate and / or hafnium, doped or not, said powder may have a specific surface area greater than 100 m ² / g, greater than 200 m ² / g, greater than 250 m ² / g, greater than 300 m ² / g and / or less than 380 m7g and the sum of the mesoporous and microporous volumes of the powder may be greater than 0.10 cm ³ / g, greater than 0.15 cm ³ / g, greater than 0.20 cm ³ / g and / or less than 0, 30 cm ³ / g.

When the porous base particles are ZrC 2 zirconia and / or HfO ₂ hafnium oxide, said powder may have a specific surface area greater than 20 mVg, greater than 50 m ² / g, greater than 70 m ² / g, greater than 100 m ² / g and / or less than 200 m ² / g and the sum of the mesoporous and microporous volumes of the powder may be greater than 0.08 cm ³ / g, greater than 0.10 cm ³ / g, greater than 0.20 cm ³ / g and / or less than 0.30 cm ³ / g. For a particle powder having all dimensions greater than 50 nm, (ie when more than 95% by number of the basic particles have dimensions all greater than 50 nm), the inventors consider that the characteristic "Having a specific surface area greater than 10 m ² / g and a sum of mesoporous and microporous volumes greater than 0.05 cm ³ / g" is substantially equivalent to the characteristic "having a porosity index I p greater than or equal to 2".

The invention thus relates to a powder of particles such as those described above in which the characteristic "Ip greater than or equal to 2" or the "porous" character would be replaced, when all the dimensions of the basic particles are greater than 50 nm. , by the characteristic "having a specific surface area greater than 10 mVg and a sum of mesoporous and microporous volumes greater than 0.05 cm / g".

Conversely, the invention relates to a powder of particles such as those described above in which the characteristic "Ip less than 2" or the "dense" character would be replaced, when all the dimensions of the base particles are greater than 50 nm, by the characteristic "having a specific surface area of less than 10 m ² / g and a sum of mesoporous and microporous volumes of less than 0.05 cm ³ / g".

When the dense basic particles of a powder according to the invention are a zirconium derivative and / or hafnium doped or not, and in particular a basic sulfate of zirconium and / or hafnium doped or not, a basic phosphate of zirconium and / or hafnium doped or not, a basic carbonate of zirconium and / or hafnium doped or not, or a mixture of these derivatives, said powder may have a specific surface area of less than 7 m ² / g and the the sum of the mesoporous and microporous volumes of the powder may be less than 0.05 cm ³ / g. When the dense base particles of a powder according to the invention are ZrO ₂ zirconia and / or HfO ₂ hafnium oxide, said powder may have a specific surface area of less than 7 m ² / g, or even less than 5 m ² / g and the sum of the mesoporous and microporous volumes of the powder may be less than 0.02 cm ³ / g,

In general, the invention relates to a powder obtained or obtainable according to a process according to the invention, in particular by a process comprising a step e1) of calcination at a temperature below 1200 ° C.

A powder according to the invention may also comprise one or more of the following optional characteristics:

The maximum size (Dc s) of the particles of the powder (basic or aggregated) is less than 150 microns, less than 100 microns, less than 80 microns, or less than 50 microns. The particles are insoluble in water. - More than 20%, more than 50%, more than 80%, more than 90%, or even more than 95%, or even substantially 100% by number of the basic particles, independent or constituting an aggregated particle, have a form chosen from a wafer, in particular a wafer with a thickness greater than 50 nm and / or a needle, in particular a needle with a length greater than 200 nm. - At least 80%, preferably at least 90%, or even substantially 100% by number of said particles are ordered aggregated particles, in particular in a lamellar form, in particular consisting of 2 to 50 platelets, star, including branches tapered and / or rectilinear, or even having only such branches, in particular having 3 to 15 branches, preferably having more than 3, 4 or 5 branches, and in sphere, in particular hollow sphere, preferably having a sphericity index greater than 0.7, and / or are aggregated disordered particles, in particular in the form of sea urchins.

The aggregated particles may in particular result from a combination of basic particles into a needle or wafer. These basic particles can themselves be assembled as intermediate aggregated particles: For example, aggregated particles may consist of an assembly of stars or an assembly of stars and needles.

The aggregated particles consist of base particles whose dimensions are greater than 250 nm.

All sizes of the base or aggregate particles are greater than 50 nm, greater than 100 nm, greater than 200 nm, greater than 250 nm, greater than 500 nm, and even greater than 600 nm. A size greater than 50 nm is particularly advantageous for creating pores allowing a good diffusion of gases, and therefore to achieve good catalytic performance or filtration. The particles may be anisotropic, in particular having a wafer shape or having a needle shape, in particular of a length greater than 200 nm. At least 95% in number or even substantially 100% by number of the base particles have a shape such that all its dimensions are greater than 50 nm. The base particles have a shape different from that of a wafer, needle or lamella, in particular when they have at least one dimension less than 50 nm.

The particles are doped and the dopant of the particles is chosen from compounds of an element chosen from yttrium Y, scandium Sc, cerium Ce, silicon Si, sulfur S, aluminum Al, calcium Ca, magnesium Mg and their mixtures.

"If the particles are zirconia and / or hafnium oxide particles, the doping compound may in particular be an oxide of an element selected from Y, La, Ce, Sc, Ca, Mg and mixtures thereof, solid solution with zirconium oxide and / or hafnium oxide, preferably in a molar amount of less than or equal to 20%, in particular a zirconia powder doped with yttrium oxide or a ceria doped zirconia, an oxide of an element selected from Si, Al, S and mixtures thereof dispersed in zirconium oxide and / or hafnium oxide. aluminum oxide, preferably its molar amount is lower or equal to 20%, more preferably less than or equal to 3%;

If the particles are particles of zirconium and / or hafnium hydrates, the doping compound may in particular be a hydrate of an element chosen from Y, La, Ce, Sc, Ca, Mg and mixtures thereof. in intimate molecular admixture with zirconium and / or hafnium hydrate, preferably in a molar amount of less than or equal to 20%. The invention relates in particular to a powder of a mixed hydrate of zirconium and yttrium, and / or a mixed hydrate of zirconium and cerium; an aluminum hydrate dispersed in zirconium hydrate and / or hafnium, preferably in a molar amount of less than or equal to 20%, more preferably less than or equal to 3%; an oxide of an element selected from Si, S and mixtures thereof, dispersed in zirconium hydrate and / or hafnium.

If the particles are particles of a zirconium and / or hafnium derivative, the doping compound may in particular be a derivative of an element chosen from Y, La, Ce, Sc, in an intimate molecular mixture with the zirconium and / or hafnium derivative, preferably in a molar amount of less than or equal to 20%. The invention particularly relates to a powder of a mixed derivative of zirconium and yttrium or a mixed derivative of zirconium and cerium; a salt of an element selected from Ca, Mg and mixtures thereof, in an intimate molecular mixture with the zirconium and / or hafnium derivative, preferably in a molar amount of less than or equal to 20%; an aluminum hydrate, in an intimate molecular mixture with the zirconium and / or hafnium derivative or located on the surface of the zirconium and / or hafnium derivative, preferably in one molar amount less than or equal to 20%, more preferably less than or equal to 3%; an oxide of an element selected from Si, S and mixtures thereof, in an intimate molecular mixture with the zirconium and / or hafnium derivative or located on the surface of the zirconium and / or hafnium derivative,

Preferably, the molar amount of dopant is determined to be less than 40% or even less than 20% or even less than 10% or even less than 5% or even less than 3% of the mass of the particulate material. - The particle powder has a specific surface area preferably greater than 10 m ² / g, or even greater than 20 m ² / g, or even greater than 50 m ² / g, or even greater than 100 m ² / g. The sum of the mesoporous and microporous volumes of the powder is preferably greater than 0.05 cm ³ / g, or even greater than 0.1 cm ³ / g, or even greater than 0.15 cm ² / g. - Whatever the embodiment, preferably, the impurity content of a powder according to the invention is less than 0.7%, preferably less than 0.5%, preferably less than 0.3%, more preferably less than 0.1%, in percentages by mass of dry matter.

The invention also relates to a powder having a maximum particle size (D _99: j) of less than 200 μm and having a porosity index Ip of less than 2, the porosity index being equal to the ratio A _sr / A _sg where

A _sg is the theoretical geometric specific area calculated from the shape and particle size determination of the powder; - A _sr is the measurement of the actual specific area by BET; said powder comprising more than 20% by number of base particles having a sphericity index of less than 0.6, aggregated in the form of stars comprising from 3 to 15 branches, in particular fused and / or rectilinear, or lamellae consisting of 2 to 50 platelets, and - consisting of a zirconium and / or hafnium oxide of formula MO _x , M being Zr ⁴⁺ , Hf ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , and x being a nonzero positive number. Insofar as they are not incompatible with this embodiment, the characteristics of a powder according to the embodiment described above are applicable to this powder.

The invention also relates to a powder having a maximum particle size (D _{99> 5} ) of less than 200 μm and having a porosity index Ip of less than 2, the porosity index being equal to the ratio A _sr / A _sg where

A _sg is the theoretical geometric specific area calculated from the shape and particle size determination of the powder; A _sr is the measurement of the actual specific area by BET; said powder having more than 20% by number of base particles having a sphericity index of less than 0.6, and consisting of a zirconium oxide and / or hafnium of formula MO _x , M being Zr ⁴⁺ , Hf ^{4 +} , or a mixture of Zr ⁴⁺ and Hl ⁴⁺ , and x being a nonzero positive number, said oxide, called "first oxide", being doped by means of a dopant chosen from:

a second oxide of an element chosen from Y, La, Ce, Sc, Ca, Mg and their mixtures, in solid solution with said first oxide;

a second oxide of an element chosen from Si, Al ₁ S and their mixtures dispersed in said first oxide;

- and their mixtures.

Insofar as they are not incompatible with this embodiment, the characteristics of a powder according to the previously described embodiments are applicable to this powder. Preferably, said base particles have a wafer shape and / or are aggregated in the form of stars and / or lamellae and / or sea urchins and / or hollow spheres.

The invention also relates to a structural body, in particular manufactured by extrusion techniques, granulation (for example by atomization), injection molding, pressing (unidirectional pressing, hot pressing, CIP, HIP ...), casting (slip casting, strip casting, ...), coating (by centrifugation or "spin coating", by dipping or dip coating, chosen from a body having a density greater than 98% of the theoretical density of the material constituting it, a body having a porosity index Ip> 2, a layer with a thickness of less than 1 mm having a porosity index Ip> 2 or a density greater than 98% of the theoretical density of the component material, including a catalytic coating or "washcoat" in English, for example, obtained by dip coating or by spin coating or by strip casting, said body or said layer being obtained from a powder according to the invention.

The invention also relates to the use of a powder according to the invention or a body according to the invention as a catalyst, as a support for a catalyst, as a filtering element, in particular for the treatment of gases or liquids, as an element. a fuel cell, in particular an anode or an electrolyte, in particular a SOFC type fuel cell, as a piezoelectric material, as an optical connector, as a dental ceramic or, more generally, as a structural ceramic, that is to say in any application where good mechanical properties and / or good resistance to wear are sought.

The invention also relates to a catalyst, a support for a catalyst, a filter element, in particular for the treatment of gases or liquids, an element of a fuel cell, in particular an anode or an electrolyte, in particular a fuel cell of the SOFC type, a piezoelectric material, an optical connector, a dental ceramic or, more generally, a structural ceramic, that is to say a part exhibiting good mechanical properties and / or good resistance to wear, remarkable in that it comprises or is obtained (e) from a powder according to the invention.

Brief description of the figures

Other characteristics and advantages of the invention will become apparent on reading the detailed description which follows and on examining the appended drawing in which - FIG. 1 represents a diagram describing the main steps of a method according to the invention. invention; Figures 2a to 2e show needle, wafer, lamella, star and hollow sphere particle patterns, respectively; Figures 3a to 3h show photographs of particle powders.

Definitions

The percentiles or "percentiles" 0.5 (D _0.5 ), 50 (D ₅₀ ), and 99.5 (D ₉ ^ s) are the particle sizes of a powder corresponding to the percentages by weight, of 0, 5% of 50% and 99.5%, respectively, on the cumulative size distribution curve of the particle sizes of the powder, the particle sizes being ranked in ascending order. For example, 99.5% by mass of the powder particles have a size of less than 099.5 and 0.5% of particles by weight have a size greater than 0 ₉ 9.5. 0.5% by weight of the particles of the powder have a size less than C 1 _S. Percentiles can be determined using a particle size distribution using a sedigraph. The sedigraph used here is a Sedigraph 5100 from Micromeritics®. D ₅₀ corresponds to the "median size" of a set of particles, that is to say to the size dividing the particles of this set into first and second populations equal in mass, these first and second populations comprising only particles having a size greater or smaller respectively than the median size. The "maximum particle size of a powder" is the 99.5 percentile (099.5) of said powder.

A "powder" is a set of particles. These particles can be "basic", that is to say, not associated with other basic particles, "agglomerated" or "aggregated". Unlike a simple agglomerate of basic particles, an aggregated particle, also called "aggregate", does not dissociate easily and resists, for example, in the case of ultrasound application. Conventionally, the bonds between base particles in an aggregated particle are chemical bonds while in an agglomerate, they result from effects of charge or polarity.

In the present description, the term "particles" is defined as the base particles and the aggregates. By "impurities" is meant the inevitable constituents, necessarily introduced with the raw materials or resulting from reactions with these constituents. Here, by "impurities" is meant any element different from the zirconium compound and / or hafnium (derivative, hydrate or oxide), and optional dopant (s). Content Impurities of a "hydrate" or a "derivative" is measured after calcination at 1000 ^° C. In the case of a derivative, the element (s) of the anionic group (s) of said derivative are not considered as impurities. For example, after calcination at 1000 ^° C. of a ZBS _5, the residual sulfur is not considered as an impurity. The term "dopant" or "doping compound" of a product is a minor constituent, that is to say one which does not constitute the constituent having the highest molar content in the material under consideration. For example, an alumina doped zirconia contains a molar amount of alumina less than or equal to that of zirconia. In contrast, for example, cerium oxide of the compound of formula Ce _0.5 _{Zr 5} θ _2, described in the article "Preparation of Mesoporous This ₀ ^ ₀₁₅ Zr O ₂ mixed oxide by Hydrothermal Method Templating" Journal of Rare Earths 25, 2007, 710-714, is not a dopant. By extension, the term "dopant" is also used to refer to the species introduced during the process for manufacturing the doped product. The latter dopant may be identical to the dopant present in the doped product, or be different, that is to say constitute a precursor of the dopant present in the doped product. The dopant present in the doped product can then also be described as a "successor" of the dopant introduced during the manufacture of the doped product. For example, the addition of YCl ₃ can lead to a basic zirconium sulfate doped with yttrium basic sulfate.

The dopant of a particle can be located: - at the interior of the particle in the form: o of a compound defined (e.g. Zr0S04, ZrCeO ₄₎ or a solid solution or a molecular intimate mixture ( for example (Zr _x Yy) BS, (Zr _x CCy) O ₂ , with x + y = 1) and / or o of a dispersion (for example dispersion of alumina in a zirconia particle) and / or o inclusions and / or at the surface of the particle.

A compound of the form M (OH) _x (N ') _y (OH ₂ ) _{Z 5} M, which is a metal cation or a mixture of metal cations and N' is an anion or a mixture of anions, is generally referred to as "derivative". indices x and y being strictly positive numbers, the index z being a positive or zero number and having a solubility in water at a temperature below 20 ^° C. of less than 10 ^-3 mol / l (in contrast, for example, a salt of zirconium such as zirconium oxychloride octahydrate, to which the method described in "Zirconia Needles Synthesized Inside Hexagonal Swollen Liquid Crystals", Chemistry of Materials, 2004, 16, 4187-4192). The anions can be both inorganic (Cl ^" ) and organic (CH ₃ -COO ^' acetate), monoatomic (F ^' ) or polyatomic (SO ₄ ^2" ).

Especially if M is Zr ⁴⁺ , Hf ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , the derivative will be said

"Zirconium derivative", "hafnium derivative" or "zirconium and hafnium derivative", respectively.

Steps b) and c) in particular make it possible to manufacture zirconium and / or hafnium derivatives.

Unless otherwise stated, in the present description and claims, a "derivative" is a derivative capable of being manufactured by a process according to the invention. The term "zirconium basic sulphate" or "ZBS" is a zirconium derivative of general formula Zr (OH) χ (SO ₄ ) _y (H ₂ O) ₂ , with y between 0.2 and 2, x such that x + 2y = 4, and z a positive or zero number.

"Zirconium basic carbonate" or "ZBC" is a zirconium derivative of general formula Zr (OH) _x (COa) (H ₂ O) ₂ , with y between 0.2 and 2, x such that x + 2y = 4, and z is a positive number or zero. the term "basic zirconium phosphate" a zirconium compound of formula Zr generic (OH) _x (Pθ ₄₎ _y (H ₂ O) _z, with y between 0.2 and 2, x such that x + 3y = 4, z a positive number or zero.

A "salt" is a compound of the form M (OH) _x (N ') _y (OH 2) _z , where M is a metal cation or a mixture of metal cations and N' is an anion or a mixture of anions. x, y and z being positive or zero numbers, x + y> O ₅ and having a solubility in water at a temperature below 20 ⁰ C greater than 10 ^"3 mol / 1. The anions may be as well inorganic (Cl ^") and organic (acetate CH ₃ ^-COO") monoatomic (F ^") as well as polyhydric (SO4 ^2"). in the case of zirconium, typical salts are zirconium oxychloride Zr (OH) ₂ Cl ₂ (OH ₂ ) ₄ , zirconium chloride ZrCl ₄ and zirconium sulfate Zr (SO ₄ ) ₂ Zirconium oxychloride or ZOC is the crystallized zirconium salt of formula Zr (OH) ₂ Cl ₂ (OH ₂ ) ₄ . A compound of the form MO _x (OH) _y (OH 2) _z is conventionally called "hydrate", M being a metal cation or a mixture of metal cations, the indices x and z being positive or zero numbers, the index y being a positive number, and 2x + y being equal to the valency of the cation or equal to the average valence of the cation mixture. For example, zirconium hydrates, or "ZHO", have the formula ZrO _x (OH) _y (OH ₂ ) _2j with z> O, y> 0 and 2x + y = 4.

In particular if M is Zr ⁴⁺ , Hf ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , the hydrate will be a "zirconium hydrate", "hafnium hydrate" or "zirconium hydrate and hafnium ", respectively. If x and z are zero, the hydrate will have the formula Zr (OH) ₄ and will also be called "zirconium hydroxide".

According to this definition, a hydrated zirconia, of general formula of the Zrθ2.n (H ₂ O) type, is not a hydrate within the meaning of the invention.

By definition, a hydrate has a solubility in water at a temperature below 20 ^° C. of less than 10 ³ mol / l. Unless otherwise stated, in the present description and claims, a "hydrate" is a hydrate capable of being manufactured by a process according to the invention. A compound of formula MO _x is conventionally called "oxide", M being a metal cation or a mixture of metal cations, and x a non-zero positive number. For example, zirconia ZrO ₂ is a zirconium oxide. In the particular case of sulfur and phosphorus, the compounds in the oxide form also include all oxidized compounds of sulfur and phosphorus respectively. An oxidized sulfur compound is for example SO4 ^{2 *} , an oxidized phosphorus compound is for example PO ₄ ^{3 '} . In the absence of contrary indications, in the present description and claims, an "oxide" is an oxide capable of being manufactured by a process according to the invention. The term "oxoanion" is conventionally referred to as an oxide-containing anion, of the form QOx ^{11 '} , Q being a metal (for example silicon) or a non-metal (for example carbon, phosphorus or sulfur), n being a an integer greater than or equal to 1 and x being equal to (n + w) / 2, with w the valence of the metal or non-metal considered. The term "calcination" is a heat treatment that makes it possible to transform a product into an oxide form. Typically the calcination is carried out at a temperature of 500 ^° C. and higher. "Drying" is a heat treatment, generally carried out at a temperature below 400 ^° C., which makes it possible to eliminate all the solvent, or even only the solvent that does not participate in the constitution of the dried product. For example, in the case where the solvent is water, the drying of a zirconium hydrate will eliminate water not being the water of constitution of said hydrate. Unlike calcination, drying does not lead to transformation of the treated product into an oxide form. "Open porosity" is defined as the porosity attributable to all accessible pores of a material in the form of a powder or a shaped solid. According to the classification of the International Union of Pure and Applied Chemistry, 1994, vol.66, n ° 8, pp.1739-1758, the accessible pores are divided into 3 categories according to their equivalent diameter:

macropores are accessible pores having an equivalent diameter greater than 50 nm; mesopores are accessible pores having an equivalent diameter of between 2 and 50 nm;

the micropores are accessible pores having an equivalent diameter of less than 2 nm; the equivalent diameter of a pore being defined by the smaller dimension of said pore, as indicated in the IUPAC document. For example, if the pore is cylindrical, the equivalent diameter will be the diameter of the cylinder.

"Open porosity" is the sum of macroporosity, mesoporosity and microporosity.

In each of these categories, the term "pore volume" is conventionally referred to as the volume occupied by the accessible pores of the particles relative to the mass of the powder or of the body in question. The "macroporous volume", "the mesoporous volume" and "the microporous volume" are the volumes relative to the mass of powder or solid corresponding to macropores, mesopores and micropores, respectively. The macroporous volume is conventionally measured by mercury porosimetry; the mesoporous volume and the microporous volume are conventionally measured by adsorption and desorption of nitrogen at -196 ^° C.

A "porogenic" agent is an agent which, introduced in step a) in the mother liquor, leads to the creation of pores, mostly open, in the particles. The "porosity index" I _p of a particle powder or a body, the ratio

A _sr / A _S g where

A _sg is the theoretical geometric specific area calculated from the shape and particle size determination of the powder or body;

A _sr is the measurement of the actual specific area by BET.

Thus, if I _p = 1, ie A _sr = A _sg , the particles of the powder or of the body do not exhibit open porosity and are perfectly dense. In practice, where I _p > 2, ie A _sr > 2A _sg , the particles of the powder or of the body have a significant open porosity, and are here described as "porous particles"; o if I _p <2, the particles of the powder or of the body are not very porous and are here called "dense particles".

The porosity index characterizes the open porosity of the particles of the powder or the body (microporosity, mesoporosity and macroporosity).

The term "porous aggregate", "porous agglomerate" or "porous solid body" means an aggregate, agglomerate or solid body, respectively, having a porosity index I _p > 2.

When two compounds "and mixtures thereof" are mentioned, not only these two compounds are included, mixtures of these compounds in which the grains of the compounds are clearly distinct, but also the solid solutions and / or intimate molecular mixtures of these compounds. The "mixtures" of zirconium compounds and hafnium compounds include, for example, a solid solution of zirconium and hafnium (Zr ₅ Hf) O ₂ and a mixture of ZrO ₂ grains and HfO ₂ grains.

The acidity of a solution or suspension is equal to the concentration of H ⁺ ion, [H ⁺ ], of said solution or suspension. The acidity of a solution or suspension is also equal to 10 ^{° C.} The acidity is expressed in mol / l, and the term "textural properties" is taken to mean all the physical surface properties characterizing a powder or a body. solid shaped, namely the area specific, mesoporous volume, microporous volume, macroporous volume, pore size distribution, and average pore size.

The term "base particles" refers to the "elementary" particles, and in particular the particles in the form of a needle or a wafer: "Needle" is an anisotropic particle of generally elongate shape, that is to say extending mainly along a straight line, rectilinear or not. However, the length L, measured along this guideline, is less than 50 times the width "1", the width "1" being the largest dimension that can be measured in the set of transverse planes (perpendicular to the guideline) along the guideline. In addition, the thickness "e", i.e., the smallest dimension measured in the transverse plane in which the width "1" is measured, is greater than 0.5 times the width "1".

A needle is shown schematically in Figure 2a. Figures 3b and 3c are photographs of needle powder. The cross sections of a needle, that is to say perpendicular to the direction of the guideline defining its length, may be arbitrary, and in particular be polygonal or have the shape of an ellipse or a circle.

According to the invention, preferably 1.67 <L / 1 <50, preferably 2 <IVl, more preferably 5 <L / 1. More preferably, L / 1 <20, and preferably L / 1 <10. A "platelet" is a particle having a generally broad and shallow shape, in the manner of a straw. In other words, a plate has two large faces, generally substantially parallel to one another, spaced apart from each other by a small distance from the dimensions of said faces. A wafer is shown schematically in Figure 2b. Figure 3f is a photograph showing platelets (mixed with "bunch" particles).

More specifically, it is considered that a particle is a wafer if the length "L", corresponding to the largest dimension measurable on one of the two large faces of the particle, is less than 1.5 times the width "1", the width "1" being the largest dimension that can be measured in the set of transverse planes (perpendicular to the length) along the direction of the length, and if the thickness "e" is i.e., the smallest dimension measured in the transverse plane in which the width "1" is measured, is less than 0.5 times the width "1". According to the invention, if e, L, and 1 respectively denote the thickness, the length, and the width of a wafer, preferably e <0.25. 1, preferably e <0.22. 1 and / or L <1.2.

1.

Preferably according to the invention, the sections perpendicular to the direction of the thickness are substantially constant over the entire thickness of the wafer.

More preferably, according to the invention, the sections perpendicular to the direction of the thickness have more than 7 sides, or have the general shape of an ellipse or a circle.

Among the aggregates, one distinguishes the "ordered" forms and the "disordered" forms, according to whether the basic particles are arranged so as to constitute an aggregate of definite general shape or not, respectively. Among the ordered forms, lamellas, stars and spheres, in particular hollow spheres, are particularly distinguished.

The term "lamella" is used to refer to a particle consisting of a flat stack of at least two platelets of close dimensions, preferably with a high recovery rate. In other words, the plates are similar, in contact with their large faces and, preferably, well superimposed on each other. A coverslip is shown schematically in Figure 2c.

Preferably, a lamella in the sense of the present description and claims is such that WI VW1 <1.5 and W27W2 <1.5, - W1 and W2 designating the major axis and the minor axis, respectively, of the smallest ellipse across which each of the platelets constituting the lamella can pass, in the direction of its thickness (that is to say flat), and - Wl 'and W2' designating the major axis and the minor axis, respectively, of the smallest ellipse through which the lamella can pass, following the stacking direction.

Preferably according to the invention, the lamellae comprise less than 50, preferably less than 20 platelets.

Still preferably, according to the invention, WI VWL <1, 2 and W27W2 <1.2, more preferably W17W1 <1.1 and W27W2 <1.1, ₅ Wl W2, Wl 'and W2' are as defined above.

A "star" is a particle consisting of an assembly of at least two needles according to the invention, possibly of different dimensions, the needles crossing each other. substantially in the center of the star. A star is shown schematically in Figure 2d. The aggregation of the needles to form stars is visible in the photograph of Figure 3d. A star may result from a fixation of several needles substantially in the middle of their lengths and / or a growth of several needles from the same core (forming the heart of the star).

The length "L" of a star is called the length of the major axis of the smallest ellipse in which the star can be inscribed (see Figure 2d).

Preferably, the number of needles constituting a star is less than 15, preferably less than 8. A "sea urchin" is a particle consisting of a disordered form of base particles, and especially needles and or platelets according to the invention. Sea urchins are therefore patatoids of indeterminate shape, in the sense that the general shape of a sea urchin can be very different from that of another sea urchin. The aggregation of needles and stars to form sea urchins is visible in the photograph of Figure 3e. A hollow sphere is an isotropic particle having a central cavity such that if D denotes the largest outer diameter of the particle (its largest outside dimension) and D 'is the largest inside diameter of the cavity (its largest internal dimension), D / D '<2. A hollow sphere is schematically shown in section in FIG. 2e. An aggregation of needles to form hollow spheres is visible in one of the photographs of Figure 3g.

A hollow sphere according to the invention is preferably made of needles.

Preferably, according to the invention, the sphericity index of a hollow sphere is greater than

0.7, more preferably greater than 0.8.

The term "sphericity index" is the ratio between the smallest dimension and the largest dimension of a particle, the dimensions being measured "overall" along axes passing through the barycenter of the particle.

A particle is called "isotropic" if its sphericity index is greater than 0.6. A particle is said to be "anisotropic" if its sphericity index is between 0.02 and 0.6. For example, 0.02 is the sphericity index of a needle whose length L is 50 times greater than the thickness e. The sphericity index may be greater than 0.05 (length-to-thickness ratio equal to 20), or even greater than 0.1 (L / e ratio of 10). The index of sphericity may be less than 0.5, or even less than 0.4, or even less than 0.35, or even less than 0.3.

"Starting particle" means particles used to implement a method according to the invention. The nature of the starting particles is therefore variable according to the method under consideration.

In all the compound formulas, the indices are conventionally molar indices.

Characterization methods Particle morphology, except hollow spheres

The presence of particles having particular morphologies is generally possible by the observation of snapshots taken by scanning electron microscope as those of the figures.

These pictures also make it possible to evaluate the dimensions of the particles. In particular, when the particles of the observed powder appear to have substantially all the same morphology, it is possible to determine the average dimensions of all of these particles.

Morphology of hollow spheres

After resin coating and fine polishing (finishing with micron diamond paste) of a sample to be characterized, images comprising between 10 and 50 hollow spheres are made using a scanning electron microscope, the initial magnification (xlOOO ) used being adapted to achieve the number of hollow spheres to be observed. A large number of shots is necessary, generally more than 50. On the one hand the orientation of each hollow sphere being random and on the other hand the polishing allowing a random section of each hollow sphere, it is then possible to determine the internal structure (cavity). From these images, it is also possible to evaluate, on average on a set of particles, the largest outside diameter of the cavity D and the largest inside diameter of the cavity D '.

Chemical analyzes The determination of chloride ions Cl ^' is carried out after pyrohydrolysis by ion chromatography. The contents of carbonate (CO ₃ ² ) and sulphate (SO ₄ ^{2 "} ) are determined from the carbon and sulfur contents (respectively converted into CO ₃ ^2" and sulphate SO ₄ ^{2 '} ) measured on a carbon Sulfur analyzer, LECO model CS-300.

For the other elements, if the content of the element is greater than 0.1% by mass, it is determined by X-ray fluorescence spectroscopy; if the content of an element is less than 0.1% by weight, it is determined by ICP (Induction Coupled Plasma) on a Vista AX model (marketed by Varian).

Loss on ignition The loss on ignition is determined by measuring the loss of mass of the product after calcination of the product at 1000 ^° C. for 1 h.

Measurements of specific surface area and mesoporous and microporous volumes

The textural properties are determined by physical adsorption / desorption of N ₂ at -196 ° C on a Nova 2000 model marketed by Quantachrome. The samples are desorbed beforehand at 250 ^° C. for 2 hours for the calcined powders or calcined solid bodies and at 100 ^° C. for 2 hours for the non-calcined powders. The specific surface area is calculated by the BET method (Brunauer Emmet Teller) as described in Journal of the American Chemical Society 60 (1938) pages 309 to 316. The mesoporous and microporous volumes as well as the size distribution of the mesopores and micropores are determined by the BJH method [described by EP Barrett, LG Joyner, PH Halenda, J. Am. Chem. Soc. 73 (1951) 373] applied to the desorption branch of the isotherm.

Determination of geometric specific area A _sg The geometric specific area of the particles of a powder or body is determined from observations made by SEM scanning electron microscopy. The geometric specific area A _sg is given by formula (1):

with pi the theoretical density of the material (determined by Helium intrusion) of the particle i, d ₁ and Di respectively the smallest dimension and the largest dimension of the particle i measured "overall" along axes passing through the barycentre of the particle i, and n the number of particles that have been measured, with n> 200. In the case of aggregated particles, n refers to the number of aggregated particles, and not to the number of basic particles constituting them.

Macroporous volume measurement

The macroporous volume as well as the size distribution of the macropores are determined by Hg porosimetry on a Porosizer 9320 model marketed by Micromeritics. The samples are introduced in the form of powder or shaped solid. The maximum applied pressure of 6000 psi makes it possible to measure the porosity for pore diameters greater than 50 nm.

Determination of crystalline structure (XRD analysis)

The X-ray powder diffraction patterns were obtained on a BRUKER ^' D5005 diffractometer, using copper Ka radiation (1.54060 Å). The intensity data are recorded over a 2Θ interval of 3-80 ° with a step of 0.02 ° and a counting time of Is per step. The crystalline phases are identified by comparison with the standard JCPDS files.

The crystalline structure can be confirmed by other well known methods such as Raman spectroscopy or, locally at the level of a base particle, by transmission electron microscopy.

Determination of particle size distribution

The particle size distribution of the particles is determined by sedigraphy on a sedigraph model Sedigraph 5100 marketed by Micromeritics. The sample to be characterized is suspended in a solution containing sodium metaphosphate and then dispersed twice for 3 minutes under ultrasound (power of 70 W). The suspension is then introduced with stirring into the equipment for analysis.

detailed description An embodiment of a method according to the invention comprising steps a) to e) as described above is now described in detail. Step a)

In step a), the polar solvent [1] may be selected from water, alcohols, organic solvents and mixtures thereof. Preferably, the polar solvent is water.

The first reagent [2] is selected to provide Zr ⁴⁺ and / or Hf ⁴⁺ ions. Preferably, it is soluble in the solvent of the mother liquor. More preferably, it can be chosen from:

the zirconium and / or hafnium salts soluble in said solvent, such as, for example, chlorides, oxychlorides, sulphates, oxynitrates, acetates, formates, citrates; alkoxides of zirconium and / or hafnium, such as, for example, butoxides and propoxides;

acid-soluble zirconium and / or hafnium derivatives in said solvent, such as, for example, basic carbonates, hydroxides; and their mixtures.

Preferably, the first reagent is chosen from the solvent-soluble zirconium and / or hafnium salts and their mixtures, preferably from oxychlorides, oxynitrates and their mixtures, more preferably from oxychlorides. The second reagent is chosen so as to provide anionic groups so as to form in step b), by precipitation with the Zr ⁴⁺ and / or Hf ⁴⁺ ions provided by the first reagent, a zirconium derivative and / or hydrolyzable hafnium, preferably anisotropic. The second reagent [3] is preferably chosen so as to provide the anionic groups SO ₄ ^{2 "} or PO ₄ ^3" and mixtures thereof. For example, the second reagent may be a mixture of Na ₂ SO ₄ and H ₂ SO 3. Preferably, the second reagent is chosen so as to provide anionic groups SO ₄ ^{2 "} . With a first reagent supplying Zr ⁴ ions. ⁺ , second reagents providing anionic groups SO ₄ ^{2 "} or PO ₄ ^3" lead to ZBS (Zirconium basic sulphate) or basic zirconium phosphate, respectively, at the end of step b). the absence of step c), they can lead to ZHO (zirconium hydrate) or ZHO particles doped at the end of step d) of basic hydrolysis of ZBS, or basic zirconium phosphate. They can also lead, in case of step ei) calcination or ₂ ) hydrothermal treatment of doped ZHO or ZHO or ZBS or ZBS doped or basic zirconium phosphate or basic phosphate doped zirconium, to particles of zirconia or doped zirconia. In a particular embodiment, the first reagent makes it possible to provide both Zr ⁴⁺ and / or Hf ⁴⁺ ions and anionic groups. For example, the first reagent may be zirconium sulphate, Zr (SO ₄ ) ₂ , which makes it possible to provide both Zr ⁴⁺ and SO ₄ ^" anionic groups.

The ratio of the concentration of anionic groups to the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ ions is preferably between 0.2 and 5. Preferably, this ratio is greater than 0.3, preferably greater than 0. , 4, more preferably greater than 0.5 and / or less than 2, preferably less than 1.5, more preferably less than 1.2. For example, the ratio of the concentration of anionic groups SO ₄ ^{2 '} to the concentration of Zr ⁴⁺ ions can be between 0.3 and 2, preferably between 0.4 and 1.5, more preferably between 0 and , 5 and 1,2.

The mother liquor must have a pH less than or equal to 7, preferably less than or equal to 6, preferably less than or equal to 4, preferably less than or equal to 2. The pH adjustment of the mother liquor can be carried out in particular by additions of acids and / or organic or inorganic bases. The additive [4] makes it possible to modify the morphology and is chosen from the group of: - anionic surfactants and their mixtures, in particular: o carboxylates (of formula R-CO ₂ ^' -G ⁺ with R an aliphatic carbon chain , aromatic or alkylaromatic and G ⁺ a monoatomic or polyatomic cation and / or a mixture of such cations), preferably chosen from ethoxylated carboxylates, ethoxylated or propoxylated fatty acids, sarcosinates of formula RC (O) N (CH ₃ ) CH ₂ COO ^' and mixtures thereof; sulphates (of formula R-SO ₃ --G ⁺ with R an aliphatic, aromatic or alkylaromatic carbon chain and G ⁺ a monoatomic or polyatomic cation and / or a mixture of such cations), preferably chosen from alkyl sulphates, alkyl ether sulphates or sulphates of ethoxylated fatty alcohols, nonylphenyl ether sulphates, and mixtures thereof; sulphonates (of formula R-OSO ₃ ^' -G ⁺ with R an aliphatic, aromatic or alkylaromatic carbon chain and G a monatomic or polyatomic cation and / or a mixture of such cations), preferably chosen from alkylarylsulphonates including sulphonates dodecylbenzene and tetrapropylbenzene sulphonates, sulphonated α-olefins, sulphonated fatty acid and fatty acid esters, sodium sulphosuccinate and sulphosuccinamate, sulphosuccinic acid mono and di-esters, sulphosuccinic acid monoamides, N-acylamino acids and N-acylproteins, N-acylaminoalkylsulfonates and taurinates, and mixtures thereof; o phosphates (of formula R '- (RO) _n Pθ ₄ -n ^{(3 "n)'} - (3-n) G ⁺ with R and R 'of the aliphatic, aromatic and / or alkylaromatic carbon chains, G a cation monoatomic or polyatomic and / or a mixture of such cations, preferably selected from H ⁺ , Na ⁺ and K ⁺ , and n an integer less than or equal to 3), preferably selected from mono- and diesters of the phosphoric acid, and mixtures thereof;

amphoteric surfactants and mixtures thereof, in particular: betaines of formula RR ¹ NH-CH ₃ COO ^" with R and R ', aliphatic, aromatic and / or alkylaromatic carbon chains, sulfobetaines, salts of imidazolium;

cationic surfactants and mixtures thereof, in particular: non-quaternary ammonium compounds (of formula R'-R _n NH ( ₄ _n ) ⁺ -X ^" with R and R 'aliphatic, aromatic and or alkylaromatic, X ^" a monoatomic or polyatomic anion and / or a mixture of such anions and n an integer less than 4); quaternary ammonium salts (of formula R 1 R ₄ N ⁺ -X ^" with R and R 'of the aliphatic, aromatic and / or alkylaromatic carbon chains and X ^* a monoatomic or polyatomic anion and / or a mixture of such anions ), preferably alkyltrimethylammonium, alkylbenzyldimethylammonium, and mixtures thereof; amine salts; o ammonium salts of ethoxylated fatty amines; dialkyldimethylammonium; imidazolinium salts;

carboxylic acids, their salts, and their mixtures, in particular the mono- or dicarboxylic aliphatic acids, in particular the saturated acids; fatty acids, and especially saturated fatty acids; formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, 2-ethylhexanoic acid, behenic acid, nonyl acid, linolenic acid, abietic acid, oleic acid, recinoleic acid, naphthenic acid, phenylacetic acid; dicarboxylic acids including oxalic, maleic, succinic, glutaric, adipic, pimelic, suberic, azelaic and sebacic acids. The salts of these acids can be used. The term "carboxylic acid salts" means the compounds of formula (R-COO ^" , G ⁺ ), G ⁺ being a cationic group, preferably Na ⁺ or NH ⁴⁺ .

nonionic surfactants chosen from the group of compounds of formula RCO ₂ R 'and R-CONHR' and their mixtures, R and R 'being aliphatic, aromatic and / or alkylaromatic carbon chains, and in particular: mono- and di-ethanolamides of polyethoxylated and polypropoxylated fatty acids; polyethoxylated and polypropoxylated fatty amines; o copolymers polyethoxylated and polypropoxylated blocks, such as family copolymers Pluronic ^® marketed by BASF; polyethoxylated and polypropoxylated fatty alcohols and alkylphenols chosen from ethoxylates of carboxymethylated fatty alcohols, this family including all of the ethoxylated or propoxylated fatty alcohols including at the end of the chain the group -CH ₂ -COOH, of general formula: R1- O- (CR2R3- CR4R5-O) _n -CH ₂ -COOH, Rl, R2, R3, R4 and R5 are aliphatic carbon chains, aromatic and / or alkylaromatic and n an integer; o amine oxides; alkylimidazolines; o and their mixtures;

- and their mixtures.

The additive making it possible to modify the morphology is preferably chosen from the group: anionic surfactants and their mixtures, in particular: o carboxylates (of formula R-CO ₂ --G ⁺ with R an aliphatic, aromatic carbon chain or alkylaromatic and G ⁺ a monoatomic or polyatomic cation and / or a mixture of such cations), preferably chosen from ethoxylated carboxylates, ethoxylated or propoxylated fatty acids, sarcosinates of formula RC (O) N (CH ₃ ) CH ₂ COO ^"and mixtures thereof; o sulfates (of formula R-SO ₃ with R ⁺ --g an aliphatic hydrocarbon chain, aromatic or alkylaromatic and G ⁺ a monatomic or polyatomic cation and / or a mixture of such cations), preferably selected among the alkyl sulphates, the alkyl ethersulfates or sulphates of ethoxylated fatty alcohols, the nonylphenyl ether sulphates, and their mixtures; sulphonates (of formula R-OSO ₃ --G ⁺ with R an aliphatic, aromatic or alkylaromatic carbon chain; ue and G ⁺ a monoatomic or polyatomic cation and / or a mixture of such cations), preferably chosen from alkylaryl sulphonates including dodecylbenzene sulphonates and tetrapropylbenzene sulphonates, sulphonated α-olefins, fatty acids and fatty acid esters sulfones, sodium sulfosuccinate and sulfosuccinamate, mono and di-esters of sulfosuccinic acid, monoamides of sulfosuccinic acid, N-acylamino acids and N-acylproteins, N-acylaminoalkylsulfonates and taurinates, and mixtures thereof; o phosphates (of formula R '- (RO) _n PO _4-n ^{(3 "n)"} - (3-n) G ⁺ with R and R' of the aliphatic, aromatic and / or alkylaromatic carbon chains, G ⁺ a monoatomic or polyatomic cation and / or a mixture of such cations, preferably chosen from H ⁺ , Na ⁺ and K ⁺ , and n an integer less than or equal to 3), preferably chosen from mono- and di-esters of phosphoric acid, and mixtures thereof;

cationic surfactants and their mixtures, in particular: non-quaternary ammonium compounds (of formula R'-R _n NH ( _4-n ) -X ^" with R and R 'of the aliphatic, aromatic and / or carbon chains or aromatic alkyl, X ^' a monoatomic or polyatomic anion and / or a mixture of such anions and n an integer less than 4); quaternary ammonium salts (of formula R ^ R ₄ N ⁺ -X ^" with R and R 'aliphatic, aromatic and / or alkylaromatic carbon chains and X ^" a monoatomic or polyatomic anion and / or a mixture of such anions), preferably alkyltrimethylammonium, alkylbenzyldimethylammonium, and mixtures thereof; o amine salts; ammonium salts of ethoxylated fatty amines, dialkyldimethylammonium, imidazolinium salts.

Preferably, the additive making it possible to modify the morphology is chosen from the group:

anionic surfactants and their mixtures, in particular: sulphates (of formula R-SO ₃ -G ⁺ with R an aliphatic, aromatic or alkylaromatic carbon chain and G ⁺ a monoatomic or polyatomic cation and / or a mixture of such cations), preferably selected from alkyl sulphates, alkyl ether sulphates or sulphates of ethoxylated fatty alcohols, nonylphenyl ether sulphates, and mixtures thereof; o phosphates (of formula R '- (RO) _n PO ₄ _n ^{(3') '} - (3-n) G ⁺ with R and R' of the aliphatic, aromatic and / or alkylaromatic carbon chains, and G ⁺ a monoatomic or polyatomic cation and / or a mixture of such cations, preferably chosen from H ⁺ , Na ⁺ and K ⁺ , and n an integer less than or equal to 3), preferably chosen from mono- and di-esters of phosphoric acid, and mixtures thereof; cationic surfactants and mixtures thereof, in particular: o non-quaternary ammonium compounds (of formula R'-R _n NH (4- _n ) -X with R and R 'of the aliphatic, aromatic and / or alkylaromatic carbon chains, X ^' a monoatomic or polyatomic anion and / or a mixture of such anions and n an integer less than 4); quaternary ammonium salts (of formula R 1 R ₄ N ⁺ -X ^" with R and R 'of the aliphatic, aromatic and / or alkylaromatic carbon chains and X ^" a monoatomic or polyatomic anion and / or a mixture of such anions ), preferably alkyltrimethylammonium, alkylbenzyldimethylammonium, and mixtures thereof; The additives chosen from anionic and / or cationic surfactants advantageously make it possible to increase the proportion of anisotropic primary derivative particles at the end of step b).

More preferably, the additive making it possible to modify the morphology is chosen from the group: alkyl sulphates, such as sodium dodecyl sulphate or SDS;

non-quaternary ammonium compounds (of formula R'-R _n NH ( _4-n ) -X ^" with R and R 'of the aliphatic, aromatic and / or alkylaromatic carbon chains, X ^" a monoatomic or polyatomic anion and / or a mixture of such anions and n an integer less than 4), such as cetyltrimethylammonium bromide or CTAB.

In addition to the additive which makes it possible to modify the morphology, a nonionic surfactant [5], different from those mentioned as being able to serve as an additive, may be added. This surfactant is distinguished from the additive [4] in that it does not allow, without additive, to modify the morphology of the particles obtained. Associated with an additive, it can however modify the impact of said additive. Simple tests make it possible to check whether a nonionic surfactant modifies the morphology of the particles manufactured or not. The optional surfactant may in particular be chosen from all the compounds of formula R-OR ', R-OH, R- (CH ₂ -CH ₂ -O) _n -R', the family of polyols R and R ' being aliphatic, aromatic and / or alkylaromatic carbon chains and n is an integer. The optional nonionic surfactant is preferably selected from - nonylphenol polyethoxylated and polypropoxylated (eg Triton ^® family marketed by Dow Chemicals);

polyethoxylated and polypropoxylated fatty alcohols;

polyethoxylated and polypropoxylated octylphenols; polyethoxylated and polypropoxylated fatty acid esters;

polyethoxylated and polypropoxylated fatty alcohols and alkylphenols, in particular ethylene glycol, propylene glycol, glycerol, polyglyceryl esters and their polyethoxylated and polypropoxylated derivatives and polyethylene glycols;

anhydrosorbitol esters including polyethoxylated and polypropoxylated sorbitan esters and sorbitan or sorbate esters; alkylpolyglucosides; ethoxylated and propoxylated oils; and their mixtures.

The optional nonionic surfactant may for example be an anti-foaming agent or a surface tensioning agent, for example the CONTRASPUM K1012 sold by the company Zschimmer and Schwartz. An anti-foaming agent advantageously facilitates the implementation of the process and / or increases its yield. For example, a surface tension agent may increase the effect of the additive. The definitions of the various surfactants as well as examples can be consulted in "the techniques of the engineer", volume K2 after the update n ° 52 (May 2007), surfactants K342.

The blowing agent [6] may especially be chosen from:

the family of latices, in particular from styrene acrylates and / or polymethyl acrylates, and from propionates and / or polyvinyl acetates; oxides and salts of polyethylene and / or polypropylene; and their mixtures.

The addition of a porogenic agent advantageously leads to creating porosity in the particles obtained at the end of steps b), c), d) or e). For this purpose, a step of heating these particles may be necessary in order to eliminate the pore-forming agent so that it leaves room for pores. Preferably, the amount of pore-forming agent is greater than 0.5%, preferably greater than 2% and / or less than 25%, preferably less than 10%, the percentages being percentages by weight relative to the first reagent. mother liquor.

To obtain anisotropic particles, the additive is preferably introduced into the mother liquor before the second reagent supplying the anionic groups, and immediately before or after the first reagent supplying Zr ⁴⁺ and / or Ht ⁴⁺ ions. When the mother liquor contains an "other" nonionic surfactant (i.e., a component [5]), and / or a blowing agent, these are preferably introduced into the mother liquor immediately before the introducing the second reagent, and therefore, preferably, after the introduction of the first reagent and the additive.

Failure to comply with this order may result in some additives that do not precipitate anisotropic particles. For example, with the sodium dodecyl sulfate (SDS) used as additive, particles of primary derivative of zirconium and / or hafnium anisotropic will be obtained if this additive is introduced immediately before or after the first reagent and before the introduction of the second reagent in the mother liquor. The order of introduction of the various constituents of the mother liquor may for example be: introduction of the polar solvent, introduction of the first reagent, introduction of the SDS additive, introduction of the "other" nonionic surfactant "optional" (component [5]), introducing the blowing agent, then introducing the second reagent. On the contrary, particles of primary derivative of zirconium and / or isotropic hafnium will be obtained if this additive is introduced after the second reagent and before the introduction of the first reagent into the mother liquor. With certain additives, however, the order described above is not imperative. Routine tests make it possible to evaluate the impact of the order of introduction of the constituents.

The temperature at which the mother liquor is prepared is preferably between the solidification temperature of the solvent of the mother liquor at atmospheric pressure and 50 ° C., preferably between room temperature, typically 20 ^° C. and 50 ^° C., preferably between 40 ^° C. and 50 ^° C., in order to promote the dissolution of the various components introduced into the solvent of the mother liquor, without starting any precipitation reactions of particles. After introduction of all the reagents into the mother liquor, it is maintained between the solidification temperature of the solvent of the mother liquor at atmospheric pressure and 5O ⁰ C, preferably between room temperature and 5O ⁰ C ₅ preferably between 4O ⁰ C and 50 ⁰ C, preferably for at least 15 minutes which preferably allows a better dissolution of reagents, as well as achieving good thermal and chemical homogeneity.

Step b)

In step b), the heating temperature is preferably greater than 50 ^° C. and / or less than the boiling point, preferably less than 100 ° C., preferably less than 95 ° C., preferably less than 100 ° C. 90 ^° C., preferably less than 80 ^° C., or even less than 70 ^° C. The temperature holding time Δt may be greater than 30 minutes, or even greater than 1 hour and / or preferably less than 10 hours, or even less than at 5 o'clock.

The inventors have found that beyond 10 hours of maintenance at 100 ° C., the morphology of the particles obtained is isotropic. The heating is preferably carried out at atmospheric pressure.

The rate of rise in temperature v should not be too fast to promote anisotropic growth. It is preferably less than 50 ° C / min, preferably less than 10 ° C / min. The beginning of the heating phase is defined as the moment when the mother liquor is heated, once all the constituents have been introduced.

At the end of step b), a final operation chosen from filtration, washing, acid-base neutralization, drying and combinations of these techniques may optionally be applied. All techniques known to those skilled in the art can be used. If drying is performed, an optional disagglomeration step may be performed by any technique known to those skilled in the art. The solubility of the compound obtained at the end of step b) is a function of several parameters. In particular, in order to obtain a primary derivative having a solubility in water measured at 20 ^° C. of less than 10 ^-3 mol / l, it is preferable to put under the following conditions: the concentration of H ⁺ ions in the mother liquor is preferably between

0.6 and 3 mol / l; the molar ratio of the concentration of anionic groups to the concentration of Zr ⁴⁺ and / or Hf ⁴⁺ ions in the mother liquor is preferably between 0.3 and 2;

the heating temperature of the mother liquor is preferably between 55 and 100 ^° C.

The New Treatise on Mineral Chemistry by Paul Pascal, Volume IX ₁ pages 599-61O ₁ provides detailed explanations for modifying the solubility.

At the end of step b), it is thus possible to obtain a suspension of particles or a powder of particles which, after drying, are insoluble in the polar solvent [1] and hydrolyzable. These particles are amorphous except possibly in case of addition of a dopant, as described below.

Anisotropic particles can also be obtained. If necessary, as explained above, routine tests make it possible to search for such particles.

Step c)

Step c) is optional or necessary depending on whether it is desired to manufacture a poorly soluble or acid-soluble secondary derivative in the polar solvent [1], respectively. A derivative is considered to be slightly soluble if its solubility in water at a pH of 2 is less than 10 ^-3 mol / l, otherwise the derivative is considered soluble,

In step c), the primary derivative obtained at the end of step b) may be subjected to a treatment that makes it possible to substitute partially or totally, preferably completely, the anionic groups brought by the second reagent by other anionic groups, called "Anionic substitution groups" having a high complexing power with zirconium and / or hafnium and preferably selected from oxoanions, anions of column 17 (halides), organic molecules comprising a carboxylate group (R-COO ^' ), and their mixtures. More preferably, the oxoanions are selected from phosphates, sulphates and carbonates; the halides are selected from chlorides and fluorides; the organic molecules comprising a carboxylate group are selected from formates, acetates, oxalates and tartrates. To effect said substitution, the primary derivative particles are brought into contact with a compound capable of providing the substitution anionic groups. In step c), the treatment of the primary derivative can for example be a carbonation, phosphatation, fluoridation or chlorination treatment in order to associate with zirconium and / or with hafnium an anionic group carbonate, phosphate, fluoride. or chloride, respectively.

For example, after obtaining an anisotropic ZBS at the end of step b), it can optionally be converted into anisotropic basic zirconium carbonate (ZBC) by a carbonation treatment, or converted into anisotropic basic zirconium phosphate by a treatment of phosphating. It is possible to hold the same reasoning with a basic zirconium phosphate initially. A step c) thus makes it possible to obtain compounds that are impossible to obtain in step b), for example because they are soluble in the polar solvent [1] in an acidic medium. In step c), the treatment does not modify the optionally anisotropic nature of the particles obtained in step b).

At the end of step c), a final operation chosen from filtration, washing, acid-base neutralization, drying and combinations of these techniques may optionally be applied. All techniques known to those skilled in the art can be used. If drying is performed, an optional disagglomeration step may be performed by any technique known to those skilled in the art.

Step d)

Stage d) of basic hydrolysis makes it possible to react the primary derivative obtained at the end of stage b) or the secondary derivative obtained at the end of stage c) and to transform it into zirconium hydrate and / or hafnium. This reaction makes it possible in particular to create porosity within the particles.

All techniques known to those skilled in the art can be used to perform the step d) of basic hydrolysis.

The basic hydrolysis is carried out by contacting said primary or secondary derivative with at least one source of hydroxide anions OH ^" , preferably a strong base, in particular NaOH, KOH, or with at least one amine, for the purpose of substituting the anion of said derivative by OH ^" . The primary or secondary derivative can in particular be presented in the form:

- a powder or

a suspension, directly obtained in step b) or c), or obtained after resuspension in a polar solvent, preferably in water, especially after filtration, washing and / or drying carried out in end of step b) or c). Said contacting may for example result from:

contacting a solid powder of primary or secondary derivative with a liquid basic solution; contacting a solid base with a liquid suspension of primary or secondary derivative,

contacting a liquid basic solution with a liquid suspension of primary or secondary derivative,

contacting a base in gaseous form, for example ammonia, with a liquid suspension of primary or secondary derivative, bringing a base in gaseous form, for example ammonia, into contact with a powder solid primary or secondary derivative.

If the primary or secondary derivative is in suspension in a solution, the following conditions will preferably be used: concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in said solution: preferably less than 10 mol / l and greater than 0, 01 mol / l; pH: preferably greater than 11; reaction temperature: greater than the solidification temperature of the solvent, preferably greater than room temperature, more preferably greater than 50 ° C and less than the boiling point of the solvent, preferably less than 90 ^° C.,

In the case where the suspension of primary or secondary derivative used is the mother liquor, the introduction of the hydroxide anion source (s) OH ^' is preferably carried out at a temperature below 90 ^° C. At the end of the step d), a final operation selected from filtration, washing, acid-base neutralization, drying and combinations of these techniques may optionally be applied. All techniques known to those skilled in the art can be used. If drying is performed, an optional disagglomeration step may be performed by any technique known to those skilled in the art.

Step e) In step el), the calcination conditions modify the porosity index I _n and the specific surface area of the powder. The calcination temperature may in particular be greater than 400 ^° C. and / or less than 1200 ^° C., preferably less than 1100 ^° C., more preferably less than 1000 ^° C. At temperatures greater than 1200 ^° C., the particles obtained have a low porosity index, that is to say they are dense. At temperatures below 1200 ^° C., the particles obtained are porous if the dwell time is limited. The maintenance time is generally between 1 hour and 5 hours, preferably about 2 hours.

The invention also relates to dense or porous particles obtained at the end of step e1).

In step e2), the hydrothermal treatment modifies the porosity index I _p and the specific surface area of the powder. The hydrothermal treatment temperature is higher than the boiling point of the polar solvent, preferably water, to the pressure in question, preferably greater than 130 ⁰ C ₅ and / or less than 25O ⁰ C, preferably less than 200 ° C. At temperatures above 25O ⁰ C, the particles obtained have a low porosity index, that is to say they are dense. At temperatures below 25O ⁰ C, the particles obtained are porous.

The hydrothermal treatment may be carried out by heating, in the presence of water vapor, a powder of a primary or secondary derivative, a hydrate or an oxide, said derivative, hydrate or oxide being optionally doped. This treatment can in particular be carried out with:

the use of an undried powder of primary or secondary derivative, or of hydrate, the use of a liquid suspension of primary or secondary derivative, hydrate or oxide.

If the primary or secondary derivative powder, hydrate or oxide is suspended in a solution, the following conditions are preferred: concentration of Zr ⁴⁺ and / or Hf ⁴⁺ in the total suspension: preferably less than 10 mol / l and greater than 0.01 mol / l; pH: preferably between 6 and 8;

- Reaction temperature: preferably greater than 130 ^° C, and / or less than 250 ° C, preferably less than 200 ⁰ C;

- Hold time temperature: preferably greater than 1 hour and preferably less than 10 hours.

For example, a hydrothermal treatment applied to a primary or secondary derivative of the present invention makes it possible to produce an anisotropic, possibly porous, zirconia. If the derivative is doped, the zirconia obtained will also be doped.

If a hydrothermal treatment is applied to a primary or secondary derivative, it may lead to another primary or secondary derivative, a hydrate or an oxide.

If a hydrothermal treatment is applied to a hydrate or an oxide, it can lead to a hydrate or an oxide. The invention also relates to dense or porous particles obtained at the end of step e2).

Calcination or hydrothermal treatment makes it possible to obtain novel crystallized anisotropic forms, in particular zirconium oxide and / or hafnium oxide particles doped with an oxide of an element chosen from yttrium Y, lanthanum La, cerium Ce, scandium Sc, calcium Ca, magnesium Mg and mixtures thereof, the doping oxide being in solid solution with zirconium oxide and / or hafnium oxide, or particles of oxides of zirconium and / or hafnium doped with an oxide of an element selected from Si, Al, S and mixtures thereof, the doping oxide being dispersed in the particle of zirconium oxide and / or hafnium. These particles are optionally porous if the starting particles are porous. Step e) allows for example the manufacture of a zirconium oxysulfate (crystallized, anisotropic, porous), for example ZrOSO ₄ , by calcination or hydrothermal treatment of a ZBS, or a zirconia doped with yttrium oxide in solid solution, by calcination or hydrothermal treatment of a zirconium hydrate doped with yttrium hydrate in an intimate molecular mixture. The above rules allow the skilled person to find suitable particles for a particular application by simple routine tests, and in particular to find anisotropic particles. If necessary, it is possible to implement the following experimental plan. At the end of step e), the following steps can thus be carried out: f) optionally, carrying out a first conformity test making it possible to check whether the particle powder obtained at the end of the preceding step presents a minimum percentage of particles having a size in a range of acceptable sizes included in the range 50 nm - 200 μm; and a minimum percentage of anisotropic particles; and, optionally, a porosity index, in particular greater than 2; g) if the conformity test is negative, that is to say if said powder is not in conformity, rerun of the previous steps by modifying the manufacturing conditions.

The conformity test in step f) can be, for example, considered as positive if more than 20% or even more than 50% or even more than 80%, or even more than 90%, or even more than 95% by number. particles have an anisotropic morphology and if more than 50% or even more than 80% or even more than 90% by number of the particles have a size in the acceptable size range. These criteria may in particular be used when no step d) has been carried out. To search for porous particles, the conformity test in step f) can be considered as positive if more than 20%, even more than 50%, even more than 80%, or even more than 90%, or even more than 95% in number of particles have an anisotropic morphology, and - if more than 50% or even more than 80% or even more than 90% by number of particles have a size in the acceptable size range, and if the porosity index Ip is greater than 2. These criteria can in particular be used when a basic hydrolysis step (step d)), or even a calcination step (step eθ), or even a hydrothermal treatment step (step e ₂ )) has been performed.

Modifying the conditions of basic hydrolysis and / or calcination and / or hydrothermal treatment also makes it possible to act on the porosity index. An increase in the pH during the basic hydrolysis leads to an increase in the porosity index Ip. During calcination and / or hydrothermal treatment, the index Ip decreases as the heating temperature increases and / or when the dwell time increases.

Whatever the conformity test implemented in step f), the lower limit of the range of acceptable sizes may in particular be 100 nm, 150 nm or even 200 nm and / or the upper limit of the size range. acceptable may in particular be 80 microns.

In step g), if the particles are not in conformity, it is possible in particular to determine the conditions of a new synthesis by modifying: in step a): the nature of the additive; and / or o the concentration of the additive of a concentration increment preferably greater than 5% of the initial concentration and / or less than 15% of the initial concentration, for example 10% of the initial concentration; and / or the order of introduction into the solvent of the various constituents of the mother liquor, in particular by introducing the additive before the second reagent and immediately before or after the first reagent and / or the pH, in particular by fixing it at a value less than 2; and / or the ratio between the amount of anionic groups and the amount of Zr ⁺ and Hf ⁴⁺ ions of an increment preferably greater than 0.3 and / or less than 0.6, for example 0.4; and / or - in step b): the heating temperature preferably of a temperature increment of at most 15 ° C and / or greater than 5 ° C, for example of 10 ^° C; and / or o the temperature keeping time Δt of an increment of duration preferably greater than 20 minutes and / or less than 40 minutes, for example 30 minutes; and / or the rate of rise to the heating temperature v, preferably setting it to less than 50 ° C / min, then decreasing it by an increment of 5 ° C / min; and / or during step d): the heating temperature of a temperature increment preferably at most 15 ° C and / or greater than 5 ⁰ C, for example 1O ⁰ C; and / or the pH by fixing it preferably to a value greater than 11; and / or during step ei): the heating temperature, preferably fixing it at a temperature below 1200 ^° C .; and / or o the temperature keeping time Δt of an increment of duration preferably greater than 20 minutes and / or less than 40 minutes, for example 30 minutes; and / or during step e ₂ ): the heating temperature by fixing it at a temperature preferably of less than 250 ^° C., or less than 200 ^° C.; and / or o the temperature keeping time Δt of an increment of duration preferably greater than 20 minutes and / or less than 40 minutes, for example 30 minutes. By "increment" is meant a positive or negative variation of a parameter.

The inventors have discovered and advocate the following rules:

To increase the maximum size of the particles, it is preferable, in step a), to increase the acidity of the mother liquor, and / or the ratio between the amount of anionic groups and the amount of Zr ⁴⁺ ions. and Hf ⁴⁺ , and / or the additive content and / or, in step b), increasing the heating temperature and / or the temperature holding time; to reduce the sphericity index, it is preferable, in step a), to increase the acidity of the mother liquor, and / or the ratio between the amount of anionic groups and the amount of Zr ⁴⁺ ions and Hf ⁴⁺ , and / or, in step b), decreasing the heating temperature; to promote the aggregation of the base particles, it is preferable, in step a), to reduce the acidity of the mother liquor, and / or to increase the ratio between the quantity of anionic groups and the amount of Zr ⁴⁺ and Hf ⁴⁺ ions and / or, in step b), to increase the temperature keeping time; to increase the specific surface area of the particles, it is preferable, in step a) to increase the additive content, and / or in step d) to increase the basic hydrolysis temperature, and / or to step ei) decreasing the calcination temperature, and / or in step e ₂ ) decreasing the temperature of the hydrothermal treatment. It is the same to increase the mesoporous and / or microporous volume; to increase the yield, that is to say the amount of solid material precipitated, it is preferable, in step a), to reduce the acidity and / or to choose a ratio between the quantity of anionic groups and the amount of Zr ⁴⁺ and Hf ⁴⁺ ions between 0.5 and 1.2 and / or to increase the additive content and / or, in step b), to increase the temperature of the heating and / or increase the duration of temperature maintenance.

The morphology and the sphericity index of the particles are modified by the values of the various parameters defined above. The inventors have discovered and advocate the following rules:

By modifying the parameters of a synthesis having generated needles so as to increase the ratio between the quantity of anionic groups, for example SO ₄ ^{2 "} _, and the amount of Zr ⁴⁺ and / or Hf ⁴⁺ ions and / or in order to increase the additive content, the quantity of needles relative to the quantity of isotropic particles is increased during a subsequent synthesis by modifying the parameters of a synthesis that has generated platelets so as to increase the acidity of the mother liquor and / or the level of maintenance time, the amount of platelets is increased relative to the amount of isotropic particles during a subsequent synthesis; By modifying the parameters of a synthesis that has generated stars so as to increase, in the mother liquor, the ratio between the quantity of anionic groups, for example SO ₄ ^{2 "} , and the amount of Zr ⁴⁺ ions and / or Hf ⁴⁺ and / or the additive content, the amount of stars is increased relative to the amount of isotropic particles in a subsequent synthesis;

By modifying the parameters of a synthesis that has generated sea urchins so as to increase the acidity of the mother liquor and / or with the additive content, the quantity of sea urchins is increased relative to the quantity of isotropic particles during a following synthesis; By modifying the parameters of a synthesis that has generated hollow spheres so as to increase, in the mother liquor, the ratio between the quantity of anionic groups, for example SO ₄ ^{2 "} , and the amount of Zr ⁺ ions and / or Hf ⁴⁺ and / or the acidity of the mother liquor, the amount of hollow spheres is increased relative to the amount of isotropic particles in a subsequent synthesis;

By modifying the parameters of a synthesis that has generated lamellae so as to increase, in the mother liquor, the ratio between the quantity of anionic groups, for example SO ₄ ^{2 "} , and the amount of Zr ⁺ and / or Hf ions ⁴⁺ and / or the additive content, the amount of lamellae is increased relative to the amount of isotropic particles in a subsequent synthesis;

By modifying the parameters of a synthesis having generated needles so as to reduce the additive content in the mother liquor, the needles are made thinner during a subsequent synthesis; By modifying the parameters of a synthesis having generated needles so as to increase, in the mother liquor, the ratio between the quantity of anionic groups, for example SO ₄ ^" , and the amount of Zr ⁺ and Hr ⁺ ions and / or or the acidity of the mother liquor, the quantity of stars is increased during a subsequent synthesis, the two forms being able to coexist during the transition By modifying the parameters of a synthesis which has generated needles so as to increase the acidity and / or decrease the additive content of the mother liquor, the amount of sea urchins is increased during the following synthesis, the two forms being able to coexist during the transition; By modifying the parameters of a synthesis having generated needles so as to increase the acidity and / or the duration of temperature maintenance of the mother liquor, the quantity of hollow spheres is increased, the two forms being able to coexist during the transition. ; By modifying the parameters of a synthesis which has generated sea urchins so as to increase the acidity and / or the duration of temperature maintenance of the mother liquor, the quantity of hollow spheres is increased, the two forms being able to coexist during the transition;

By modifying the parameters of a synthesis which has generated platelets so as to increase the additive content of the mother liquor, the quantity of lamellae is increased, the two forms being able to coexist during the transition. In one embodiment, the parameters of steps a) and b) are determined in order to obtain, at the end of step b), anisotropic primary derivative particles.

The following table recapitulates the preferred conditions for steps a) and b) to obtain a majority, in number, of particles having certain particular morphologies.

In the first column "*" indicates the most important parameters.

The order of introduction of the components into the mother liquor is the preferred order mentioned above.

The preceding rules and conditions, according to preferred embodiments of the invention, are not limiting. They make it possible, with the examples described below, to manufacture a powder adapted to a particular application.

In addition, the known processes applied to the currently available products have allowed the inventors to make the following observations:

the precipitation of basic solutions or the hydrolysis of derivatives known from the prior art lead to an isotropic morphology of the hydrates produced, whether there is presence or absence of surfactants;

a hydrothermal treatment carried out at a temperature greater than 200 ^° C., or even greater than 250 ^° C., of a suspension of isotropic particles or of a solution leads to powders of crystallized dense particles, possibly anisotropic. This type of hydrothermal treatment is described for example in the article "Morphology of zirconia synthesized hydrothermally from zirconium oxychloride", Journal of the American Ceramic Society, 1992, vol. 75, No. 9, pp. 2515-2519.

a hydrothermal treatment carried out at a temperature below 200 ^° C. leads to powders of isotropic particles. This type of treatment is described for example in "Nucleation and growth for nanoscale zirconia particles by forced hydrolysis", Journal of Colloid and Interface Science, 1998, vol. 198, pp 87-99. the combustion of a metal salt, the oxidation of a metal, or the calcination at high temperature of precursors lead to powders of dense particles, possibly anisotropic.

The steps of the process just described can be modified to dope the particles manufactured. A dopant or several dopants can be introduced in one or more steps, according to techniques known to those skilled in the art:

Step a)

In step a), a dopant A chosen from the compounds of elements of column 17

(halides), column 1 (alkaline) compounds, yttrium compounds

Y, Sc scandium, lanthanide, alkaline earth (elements of column 2 of the periodic table of elements), titanium Ti, silicon Si ₅ sulfur S, phosphorus

P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, gallium Ga, tin Sn ₅ lead Pb and their mixtures may be added optionally to the mother liquor. Said compounds can be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCl ₃ salt.

Preferably, the dopant A is chosen from oxides, hydrates and salts, more preferably from salts. If the dopant A is a compound of sulfur S and / or phosphorus P and mixtures thereof, preferably this compound is SO ₄ ^{2 '} and / or PO ₄ ^{3 "} , preferably introduced by the second reagent.

If the dopant A is an Al aluminum compound, it is preferably chosen from aluminum hydrates. If the dopant A is a Si silicon compound, silicon oxide is preferred.

More preferably, the dopant A is soluble in an acid medium. The dopant A is preferably chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, of scandium Sc, of lanthanum La, of Ce cerium, praseodymium Pr ₅ , neodymium Nd, calcium Ca, magnesium Mg, barium Ba, strontium Sr, titanium Ti, silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb and mixtures thereof, preferably selected from compounds of the elements of column 17 (halides), compounds of elements of column 1 (alkaline), yttrium compounds Y, scandium Sc, lanthanum Ce, Ce cerium, Ca calcium, Mg magnesium, Si silicon, S sulfur, P phosphorus, Al aluminum and mixtures thereof. More preferably, the dopant A is selected from Cl chlorine compounds, fluorine F, sodium Na, potassium K, yttrium Y ₅ scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, phosphorus P, aluminum Al and mixtures thereof. More preferably, the dopant A is chosen from compounds of yttrium Y, scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, aluminum Al and their mixtures. At the end of step b), the primary derivative obtained will then be a primary derivative of zirconium and / or doped hafnium. For example, if in step a) the stock solution contains a zirconium oxychloride, water, an additive that makes it possible to modify the morphology, a second reagent bringing the anionic groups SO ₄ ^{2 "} , and an yttrium salt YCl ₃ , the primary derivative obtained at the end of step b) will be a basic zirconium sulfate doped with a basic yttrium sulfate.

In a particular preferred embodiment, a dopant A is added during step a).

Step b)

In step b), after obtaining a suspension of particles of primary derivative, possibly doped, or of a powder of particles of primary derivative possibly doped, a dopant B chosen from the compounds of elements of column 17 ( halides), column 1 (alkaline) compounds, yttrium Y compounds, Sc scandium, lanthanides, alkaline earths (elements of column 2 of the periodic table of the elements), Ti titanium, Si silicon, Al aluminum, W tungsten, Cr chromium, Mo molybdenum, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb ₅ galium Ga, tin Sn, lead Pb and mixtures thereof may be added optionally to the mother liquor.

Said compounds can be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCl ₃ salt. Preferably, the dopant B is chosen from oxides, hydrates and salts, more preferably from salts.

If the dopant B is an Al aluminum compound, it is preferably chosen from aluminum hydrates.

If the dopant B is a Si silicon compound, it is preferably silicon oxide. The dopant B is preferably chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the yttrium compounds Y, scandium Sc ₅ of lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, calcium Ca, magnesium Mg, barium Ba, strontium Sr, titanium Ti, silicon Si ₅ Al aluminum, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga ₅ tin Sn, lead Pb and mixtures thereof , preferably chosen from the compounds of the elements of column 17 (halides), the compounds of the elements of column 1 (alkaline), the compounds of yttrium Y, of scandium Sc, of lanthan La, of cerium Ce ₅ of calcium Ca, Mg magnesium, Si silicon, Al aluminum and mixtures thereof. More preferably, the dopant B is chosen from chlorine compounds Cl ₅ of fluorine F ₅ sodium Na, potassium K, yttrium Y, scandium Sc, lanthanum La ₁ cerium Ce, calcium Ca ₅ from Mg magnesium, Si silicon, Al aluminum and mixtures thereof. More preferably, the dopant B is chosen from yttrium compounds Y, scandium Sc, lanthanum La ₅ cerium Ce, calcium Ca, magnesium Mg ₅ Si silicon, aluminum Al and mixtures thereof.

At the end of step b), the primary derivative obtained will then be a primary derivative of zirconium and / or doped hafnium. The dopant B or a successor of the dopant B may be associated with said primary derivative by any method known to those skilled in the art, for example by an impregnation process or by co-precipitation after resuspension.

The addition of a dopant A in step a) does not exclude the addition of a dopant B in step b), and vice versa.

Step c)

In step c), optional, before subjecting the primary derivative of zirconium and / or hafnium treatment intended to substitute the anionic groups of said primary derivative provided by the second reagent by other anionic groups having a high power complexing agent with zirconium and / or hamium, a Cl dopant selected from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), yttrium compounds Y, scandium Sc, lanthanides, alkaline earths (elements of column 2 of the periodic table of the elements), titanium Ti, silicon Si ₅ sulfur S, phosphorus P ₅ aluminum Al, tungsten W, chromium Cr ₅ molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu ₅ zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, Pb lead and their mixtures may be used optionally to dope said primary derivative, Lesd its compounds can be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCI ₃ salt.

Preferably, the dopant C1 is chosen from oxides, hydrates and salts, more preferably from salts. If the dopant Cl is a compound of sulfur S and / or phosphorus P and mixtures thereof, preferably this compound is SO ₄ ^{2 "} and / or PO ₄ ^3" , preferably introduced by the compound capable of providing substitution. anionic groups brought by the second reagent. If the dopant Cl is an Al aluminum compound, it is preferably chosen from aluminum hydrates. If the Cl dopant is a silicon compound Si ₅ it is preferably silicon oxide. The dopant C1 is preferably chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, scandium Sc, lanthanum La, cerium This ₅ Praseodymium Pr ₅ Neodymium Nd, calcium Ca, magnesium Mg, barium barium, strontium Sr, titanium Ti, silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn ₅ iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb and mixtures thereof, preferably selected from compounds of the elements of column 17 (halides), compounds of elements of column 1 (alkaline), yttrium compounds Y, scandium Sc, lanthanum Ce, Ce cerium, Ca calcium, Mg magnesium, Si silicon, S sulfur, P phosphorus, Al aluminum and mixtures thereof. More preferably, the dopant C1 is chosen from the compounds of chlorine Cl, fluorine F, sodium Na ₅ potassium K, yttrium Y, scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, phosphorus P, aluminum Al and mixtures thereof. More preferably, the dopant C1 is chosen from yttrium compounds Y, scandium sc ₅ of lanthanum La ₅ cerium Ce, calcium Ca ₅ magnesium Mg, silicon Si, sulfur S, aluminum Al and their mixtures. At the end of step c), the secondary derivative obtained will then be a secondary derivative of zirconium and / or doped hafnium.

The addition of a dopant A in step a) and / or the addition of a dopant B in step b) does not exclude the addition of a dopant C1 in step c), and reciprocally.

At the end of step c), optional, the secondary derivative obtained, possibly doped, can be doped with a dopant C2 chosen from the compounds of elements of column 17

(halides), compounds of column 1 (alkaline), yttrium Y, sc scandium, lanthanide, alkaline earth compounds (elements of column 2 of the periodic table of elements), titanium Ti, silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V ₅ antimony Sb, nickel Ni, copper Cu, zinc Zn ₅ iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb, cobalt Co, ruthenium Ru, rhodium rh, palladium Pd, silver Ag, Osmium Iridium Ir Os ₁ , platinum Pt, Au gold and mixtures thereof; preferably the C2 dopant is chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the yttrium Y compounds, scandium Sc ₁ of lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, calcium Ca, magnesium Mg, barium Ba, strontium Sr, titanium Ti, silicon Si, sulfur S ₅ phosphorus P, aluminum Al, tungsten W, chromium Cr ₅ molybdenum Mo, vanadium V, antimony Sb ₅ nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn ₅ niobium Nb, galium Ga, tin Sn, lead Pb ₅ cobalt Co, ruthenium Ru, Rh rhodium, Pd palladium, Ag silver, Os osmium, Ir irium, Pt platinum, Au gold and mixtures thereof. More preferably, the C2 dopant is chosen from the compounds of the elements of column 17 (halides), the compounds of the elements of column 1 (alkaline), the yttrium compounds Y, scandium Sc, lanthanum La ₅ cerium Ce ₅ calcium Ca, magnesium Mg, silicon If, sulfur S ₅ P phosphorus, aluminum Al and mixtures thereof. Preferably, the dopant C2 is chosen from chlorine compounds Cl, fluorine F, sodium Na, potassium K, yttrium Y, scandium Sc ₅ of lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, phosphorus P, aluminum Al and mixtures thereof. More preferably, the dopant C2 is chosen from compounds of yttrium Y, scandium sc ₅ of lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S ₅ aluminum Al and their mixtures.

The compounds of column 17 (halides), column 1 (alkaline) compounds, yttrium Y, lanthanide scandium Sc ₅ , alkaline earth compounds (column elements 2 of the periodic table of elements), titanium Ti, silicon If, sulfur S, phosphorus P ₅ Al aluminum, tungsten W, chromium Cr, molybdenum Mo ₅ vanadium V ₅ Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn ₅ niobium Nb, galium Ga, tin Sn, lead Pb and mixtures thereof, can be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCl ₃ salt. Preferably, said compounds are chosen from oxides, hydrates and salts, more preferably from salts. The compounds of cobalt Co, ruthenium Ru, Rh rhodium, palladium Pd, silver Ag, Iridium Ir osmium Os ₁ , platinum Pt, Au gold and mixtures thereof may be for example oxides , hydrates, salts, metals. A platinum compound may for example be a platinum salt. Preferably, said compounds of cobalt Co, ruthenium Ru, rhodium Rh, palladium Pd, silver Ag, osmium Os, iride Ir, platinum Pt, Au gold and mixtures thereof are chosen from oxides, hydrates, salts, metals, more preferably from metals.

To boost the secondary derivative, any method known to those skilled in the art, for example by an impregnation process, by co-precipitation after resuspension, may be considered.

The addition of a dopant A in step a) and / or the addition of a dopant B in step b) and / or the use of a dopant C1 in step c) n ' does not exclude the use of a C2 dopant and vice versa.

Step d)

In step d), when the primary derivative or the secondary derivative, doped or not, is in suspension, before carrying out the basic hydrolysis, a dopant D1 chosen from yttrium Y compounds, scandium Sc, lanthanides, alkaline earths (elements of column 2 of the periodic table of the elements), Ti titanium, Si silicon, sulfur S ₅ phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb and their mixtures, can optionally be added in the suspension. Said compounds can be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCl ₃ salt.

Preferably, the dopant D1 is chosen from oxides, hydrates and salts, more preferably from salts. More preferably, the dopant D1 is soluble in the polar solvent in which the primary derivative or the secondary derivative is in suspension. The dopant D1 is preferably chosen from yttrium compounds Y, scandium Sc, lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, calcium Ca, magnesium Mg, barium Ba, strontium Sr Ti titanium, Si silicon, S sulfur, P phosphorus, Al aluminum, Tungsten W, Cr chromium, Mo molybdenum, Vanadium V, Sb antimony, Ni nickel, Cu copper , Zn zinc, Mn manganese Fe ₁ iron, Nb niobium, Galium Ga, Sn tin, Pb lead and mixtures thereof, more preferably Dl dopant is selected from yttrium compounds Y, Sc scandium, lanthanum La, Ce cerium, Ca calcium, Mg magnesium, Si silicon, S sulfur, Al aluminum and mixtures thereof. The dopant D1 is preferably introduced into the solvent at the same time as the primary derivative or secondary derivative.

For example, if before carrying out the basic hydrolysis of a ZBS, an yttrium salt is added to the suspension, the hydrate obtained will be a zirconium hydrate doped with an yttrium hydrate. The addition of a dopant A in step a) and / or the addition of a dopant B in step b) and / or the use of a dopant C1 in step c) and / or a C2 dopant at the end of step c) does not exclude the addition of a dopant D1 in step d), and vice versa. In a particular embodiment, a dopant A is added to step a) and a dopant D1 in step d), dopant A being different from dopant D1. The hydrate obtained at the end of step d) is then co-doped, and for example is a co-doped zirconium hydrate.

After basic hydrolysis, the optionally doped, possibly dried, zirconium and / or hafnium hydrate may be doped with a dopant D2 chosen from the compounds of elements of column 17 (halides), the composed of elements of column 1 (alkaline), yttrium Y, scandium Sc, lanthanide, alkaline earth compounds (elements of column 2 of the periodic table of elements), Ti titanium, silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb, cobalt Co, ruthenium Ru, rhodium rh, palladium Pd, silver Ag, osmium bone, d Iridium Ir, Pt platinum, Au gold and mixtures thereof; preferably, the dopant D2 is chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, of scandium Sc, of lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, calcium Ca, magnesium Mg, barium Ba, strontium Sr, titanium Ti, silicon Si, sulfur S, phosphorus P, aluminum al ₅ W tungsten, chromium Cr, molybdenum Mo, vanadium V, Sb antimony, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, gallium Ga , Sn tin, Pb lead, Cobalt Co, Ru ruthenium, Rh rhodium, Pd palladium, Ag silver, Os osmium, Ir irium, Pt platinum, Au gold and their mixtures; more preferably, the dopant D2 is chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, scandium Sc, lanthanum La , Ce cerium, Ca calcium, Mg magnesium, Si silicon, S sulfur, P phosphorus, Al aluminum and mixtures thereof. More preferably, the dopant D2 is chosen from compounds of chlorine Cl, fluorine F, sodium Na, potassium K, yttrium Y, scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, phosphorus P, aluminum Al and mixtures thereof. More preferably, the dopant D2 is chosen from compounds of yttrium Y, scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, aluminum Al and their mixtures.

Compounds of column 17 (halides), column 1 (alkaline) compounds, yttrium Y, scandium Sc, lanthanide, alkaline earth compounds (column elements 2 of the periodic table of the elements), titanium Ti, silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb and mixtures thereof may be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCl ₃ salt.

Preferably, said compounds are chosen from oxides, hydrates, salts, and more preferably, from hydrates, where appropriate.

The compounds of cobalt Co, ruthenium Ru, Rh rhodium, palladium Pd, silver Ag, osmium Os, Ir irium, platinum Pt, Au gold and mixtures thereof can be for example oxides , hydrates, salts, metals. A platinum compound may for example be a platinum salt. Preferably, said compounds of cobalt Co, ruthenium Ru ₅ of rhodium Rh, palladium Pd, silver Ag, osmium Os, Ir irium, platinum Pt, Au gold and mixtures thereof are chosen from oxides, hydrates, salts, metals, more preferably from metals. To dope the hydrate, any method known to those skilled in the art, for example by an impregnation process, by co-precipitation after resuspension, may be used.

This doping operation can be performed several times.

The addition of a dopant A in step a) and / or the addition of a dopant B in step b) and / or the use of a dopant C1 in step c) and / or the use of a C2 dopant at the end of step c) and / or the addition of a D1 dopant before basic hydrolysis does not exclude the use of a D2 dopant after basic hydrolysis, and vice versa.

Step e)

In step e), before carrying out the calcination of the derivative obtained at the end of step b) or c), or of the hydrate obtained at the end of step d), a dopant El chosen from the compounds of elements of column 17 (halides), compounds of column 1 (alkaline), yttrium Y, scandium Sc, lanthanide, alkaline earth compounds (elements of column 2 of the periodic table of elements), titanium Ti ₅ of silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb, cobalt Co, ruthenium Ru, rhodium rh, palladium Pd, silver Ag, osmium Os, Ir iridium, Pt platinum, Au gold; and mixtures thereof can optionally be used to dope the derivative or hydrate. The dopant E1 is preferably chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, of scandium Sc, of lanthanum La, of cerium Ce, praseodymium Pr, neodymium Nd, calcium Ca, magnesium Mg, barium Ba, strontium Sr, titanium Ti, silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, Fe ₃ manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb, cobalt Co, ruthenium Ru, rhodium Rh, palladium Pd, silver Ag, osmium Os, Ir irium, platinum Pt, Au gold, and mixtures thereof; more preferably, the dopant E1 is chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, scandium Sc, lanthanum La , Ce cerium, calcium Ca, magnesium Mg, silicon Si, sulfur S ₅ phosphorus P, aluminum Al and mixtures thereof.

More preferably, the dopant El is selected from Cl chlorine compounds, fluorine F, sodium Na, potassium K, yttrium Y ₅ scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, phosphorus P ₃ aluminum Al and mixtures thereof. More preferably, the dopant E1 is chosen from compounds of yttrium Y, scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S, aluminum Al and their mixtures. Compounds of column 17 (halides), column 1 (alkaline) compounds, yttrium Y, scandium Sc, lanthanide, alkaline earth compounds (column elements 2 of the periodic table of the elements), titanium Ti, silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V, antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe, manganese Mn, niobium Nb, galium Ga, tin Sn, lead Pb and mixtures thereof may be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCl ₃ salt.

Preferably, said compounds are chosen from oxides, hydrates, salts, and more preferably, optionally, from oxides. The compounds of cobalt Co, ruthenium Ru, rhodium Rh, palladium Pd, silver

Ag, osmium Os, Ir irium, Pt platinum, Au gold and mixtures thereof can be for example oxides, hydrates, salts, metals. A platinum compound may for example be a platinum salt.

Preferably, said compounds of cobalt Co, ruthenium Ru, rhodium Rh, palladium Pd, silver Ag, osmium Os, iride Ir, platinum Pt, Au gold and mixtures thereof are chosen from oxides, hydrates, salts, metals, more preferably from metals. The oxide obtained after calcination will be a doped oxide.

Doping can be carried out by any technique known to those skilled in the art, in particular by adding a powder or impregnation by means of a suspension.

The addition of a dopant A in step a) and / or the addition of a dopant B in step b) and / or the use of a dopant C1 in step c) and / or the use of a C2 dopant at the end of step c) and / or the addition of a D1 dopant before basic hydrolysis and / or the use of a D2 dopant after basic hydrolysis does not exclude the use of an El dopant before calcination, and vice versa.

After the calcination step, the possibly doped, optionally dried, zirconium and / or hafnium oxide may be doped with an E2 dopant chosen from the compounds of elements of column 17 (halides ), compounds of column 1 (alkaline), yttrium Y, scandium Sc, lanthanide, alkaline earth (column 2 of the Periodic Table of Elements), Ti titanium , silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo ₅ vanadium V ₅ antimony Sb, nickel Ni, copper Cu, zinc Zn iron Fe ₅ ₅ ₅ Mn manganese niobium Nb, gallium Ga, Sn tin, lead Pb ₅ cobalt Co ₅ of ruthenium Ru, rhodium Rh, palladium Pd, Ag silver, osmium Bone, Irium Ir ₅ Pt platinum, Au gold and mixtures thereof; preferably, the dopant E2 is chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, of scandium Sc, of lanthanum La, of Ce cerium, praseodymium Pr, neodymium Nd ₅ calcium Ca, magnesium Mg, barium ba, strontium Sr, titanium Ti, silicon Si ₃ sulfur S, phosphorus P ₅ aluminum Al ₅ tungsten W, chromium Cr, molybdenum Mo, vanadium V ₅ antimony Sb, nickel Ni, copper Cu, zinc Zn ₅ iron Fe ₅ manganese Mn ₅ niobium Nb, galium Ga, tin Sn, lead Pb, cobalt Co, ruthenium Ru ₅ rh rhodium, palladium Pd ₅ silver Ag, osmium Os, Ir irium, platinum Pt, Au gold and mixtures thereof; more preferably, the dopant E2 is chosen from the compounds of elements of column 17 (halides), the compounds of elements of column 1 (alkaline), the compounds of yttrium Y, scandium Sc, lanthanum La , cerium Ce, calcium Ca, magnesium Mg, silicon Si, sulfur S ₁ phosphorus P, Al aluminum and mixtures thereof. More preferably, the dopant E2 is chosen from the compounds of chlorine Cl, fluorine F, sodium Na, potassium K, yttrium Y, scandium Sc, lanthanum La ₅ cerium Ce, calcium Ca ₅ of magnesium Mg, silicon Si ₁ sulfur S, phosphorus P, aluminum Al and mixtures thereof. More preferably, the dopant E2 is chosen from compounds of yttrium Y, scandium Sc, lanthanum La, cerium Ce, calcium Ca, magnesium Mg ₁ of silicon Si, sulfur S, aluminum Al and their mixtures.

Compounds of column 17 (halides), column 1 (alkaline) compounds, yttrium Y, scandium Sc, lanthanide, alkaline earth compounds (column elements 2 of the periodic table of the elements), titanium Ti ₅ of silicon Si, sulfur S, phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo ₅ vanadium V, antimony Sb, nickel Ni ₅ Cu copper, zinc Zn, iron Fe, manganese Mn, niobium Nb, gallium Ga, Sn tin, lead Pb and mixtures thereof, can be for example oxides, hydrates, salts, carbides, nitrides, metals. An yttrium compound may for example be an yttrium salt, for example YCl ₃ salt.

Preferably, said compounds are chosen from oxides, hydrates and salts, more preferably from salts.

The compounds of cobalt Co, ruthenium Ru, Rh rhodium, palladium Pd, silver Ag, osmium Os, Ir irium, platinum Pt, Au gold and mixtures thereof can be for example oxides , hydrates, salts, metals. A platinum compound may for example be a platinum salt.

Preferably, said Co cobalt compounds, ruthenium Ru, Rh rhodium, palladium Pd and silver Ag ₅ osmium Os, iridium Ir, platinum Pt, gold Au and mixtures thereof are selected from oxides, hydrates, salts, metals, more preferably from metals.

The doping of said oxide can be carried out by any method known to those skilled in the art, for example by an impregnation process.

The addition of a dopant A in step a) and / or the addition of a dopant B in step b) and / or the use of a dopant C1 in step c) and / or the use of a C2 dopant at the end of step c) and / or the addition of a D1 dopant before basic hydrolysis and / or the use of a D 2 dopant after basic hydrolysis and / or the use of an El dopant before calcination does not exclude the use of an E2 dopant after calcination, and vice versa.

In a variant of the invention, a triple doping of the zirconia is carried out by adding a first, a second and a third dopant. For example, a Y-doped ZBS derivative is made by adding an yttrium salt. Then a hydrate co-doped Y / Ce by adding a cerium salt. Finally, before calcination, an aluminum salt is added and a Y / Ce / Al doped zirconia is obtained. In general, the use of a dopant can be carried out independently of the use of one or more other dopants.

However, for the dopant to be located inside the particle in the form of a defined compound, a solid solution, or an intimate molecular mixture, it is preferable that the dopants are of type A and / or or C1 and / or D1 and / or E1. In order for the dopant to be located inside the particle in the form of a dispersion or inclusion, or to be located on the surface of the particle, it is preferable that the dopant is of type B and / or C2 and / or D2 and / or E2.

The molar quantity of dopant in the particles may be less than 40%, less than 20%, less than 10%, or even less than 5% or even less than 3%.

EXAMPLES

The following examples are provided for illustrative purposes and do not limit the invention.

Comparative Example 1: Powder Excluding Invention

11 g of zirconium oxycholide in 300 ml of deionized water are dissolved in a Pyrex 1 1 beaker, then 28 g of sodium sulphate are added and 500 ml are added to the mixture. permuted water. The acidity of the mother liquor is 1.2, the concentration of (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6 mol / l and the molar ratio between the anionic groups SO4 ^{2 "} and (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6 After complete dissolution of the reagents, the solution is brought, still with stirring, at 90 ^° C. with a heating ramp of 1 ° C./min The solution is maintained at 90 ^° C. for 1 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake obtained consists of a basic zirconium sulfate, ZBS. The powder thus obtained has a specific surface area of 3 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in a characteristic quasi-spherical form known as a "grape bunch".

In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second beaker of 1 1 teflon PTFE, 25 g of NaOH soda in 250 ml of deionized water are dissolved. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ^° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ° C for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water. on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 11 by adding 1 N ammonia (NH ₄ OH). The suspension is then filtered and then washed twice with 1 l of water. permutated water on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO. The powder thus obtained has a specific surface area of 320 m ² / g. The sum of the mesoporous and microporous volumes of 0.18 cm ³ / g and the powder is amorphous by X-ray diffraction. The ZHO particles are in a quasi-spherical form similar to that of the starting ZBS derivative.

The cake obtained is then dried in an oven for at least 12 hours at ^{0 °} C, and then stirred with agate mortar. The powder obtained is calcined under air for 2 hours (ramp temperature of 2 ° C / min, air flow rate of 100 ml / min _f is a hourly volume velocity VVH of 300 h ^-1 ) at 500 ^° C.

The powder thus obtained has a specific surface area of 60 m 2 / g; the sum of the mesoporous and microporous volumes is 0.12 cm ³ / g; the powder is crystallized in the form of a mixture of quadratic and monoclinic phases determined by X-ray diffraction. The zirconia particles are in a quasi-spherical form similar to that of the initial particles of the ZBS derivative (shown in FIG. ) and ZHO.

Example 2: Powder in the form of needles In a pyrex 1 1 beaker, 210 g of zirconium oxychloride are dissolved in 300 ml of deionized water at 50 ^° C. with stirring, then 2.5 g of sodium dodecyl sulphate or SDS, then 52 g of sodium sulphate and is added to 500 ml with deionized water, the temperature is adjusted to 50 ^° C. and maintained for 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 2, the concentration of (Zr ⁴⁺ + Hf ⁴⁺ ) is 1 mol / l, the molar ratio between the anionic groups SO ₄ ^{2 "} and (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6, and the concentration of SDS additive is 0.02 mol / 1. The presence of foam on the surface of the solution is observed.The solution is then brought, still stirring, at 70 ^° C. with a heating ramp of 1 ° C./min The solution is maintained at 70 ^° C. for 15 min and then allowed to cool freely to below 50 ^° C.

This procedure generates a suspension consisting of a solid phase and a liquid supernatant as well as foam. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake obtained consists of a basic zirconium sulfate, ZBS. The ZBS powder thus obtained has a specific surface area of 6 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of needles with a length L of between 0.5 and 3 μm. width 1 between 0.3 and 0.8 microns, and thickness e between 0.25 and 0.8 microns. For each of these hands, L / l is between 1, 67 and 50, and the thickness e is greater than 0.5 times the width 1. In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second 1 1 Teflon® PTFE beaker, 25 g of NaOH sodium hydroxide are dissolved in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water. on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 1 1 by adding 1 N ammonia (NH ₄ OH). The suspension is then filtered and then washed twice with 1 l of water. permutated water on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO.

The powder thus obtained has a specific surface area of 360 m ² / g and is amorphous by X-ray diffraction. The sum of the mesoporous and microporous volumes is 0.25 cm ³ / g. The ZHO particles are in the form of needles of length L between 0.5 and 3 μm, width 1 between 0.3 and 0.8 μm, and thickness e between 0.25 and 0. , 8 μm, similar to those of the starting ZBS derivative. For each of these needles, L / l is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1. The cake obtained is then dried in an oven for at least 12 hours at HO ⁰ C, then swept with agate mortar. The powder obtained is calcined in air for 2 hours (temperature ramp of 2 ° C./min, air flow rate of 100 ml / min, ie a VHV hourly volume velocity of 300 h ^-1 ) at 500 ^° C.

The powder thus obtained has a specific surface area of 120 m ² / g, the sum of the mesoporous and microporous volumes is 0.20 cm ³ / g and the powder is crystallized in the form of a mixture of quadratic and monoclinic phases determined by diffraction X-rays. The zirconia particles are in the form of needles of length L between 1 and 2 μm, width 1 between 0.3 and 0.8 μm, and thickness e between 0.25 and 0.8 μm, similar to the initial particles of the derivative ZBS (shown in Figure 3b) and ZHO. For each of these hands, L / l is between 1, 67 and 50, and the thickness e is greater than 0.5 times the width 1.

Example 3: Powder in the form of needles

In a beaker 1 1 Pyrex, are brought into solution at 5O ⁰ C with stirring 110 g of zirconium oxycholure in 300 ml of deionized water and then 20 g of bromide or CTAB cétyltriméthylarnmonium then added 42 g of sodium sulphate and make up to 500 ml with deionized water. The temperature is adjusted to 50 ⁰ C and maintained for 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 1.2, the concentration of (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6 mol / l, the molar ratio between the anionic groups SO ₄ ^{2 "} and (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.9, and the concentration of CTAB additive is 0.1 mol / l, the presence of foam on the surface of the solution is observed, the solution is then brought, still under stirring, to 60.degree. ⁰ C with a heating ramp of 1 ° C./min The solution is maintained at 60 ^° C. for 30 min and then allowed to cool freely to below 50 ^° C.

This procedure generates a suspension consisting of a solid phase and a liquid supernatant as well as foam. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake obtained consists of a basic zirconium sulfate, ZBS.

The ZBS powder thus obtained has a specific surface area of 3 m 2 / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of needles with a length L of between 20 and 40 μm, of width 1 included between 2 and 5 microns, and with a thickness e between 1.5 and 5 microns. For each of these needles, L / l is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1.

In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second 1 1 Teflon® PTFE beaker, 25 g of NaOH sodium hydroxide are dissolved in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then raised to 90 ^° C. with a ramp of heating of 1 ° C / min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water. on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 1 1 by adding 1 N ammonia (NH ₄ OH). The suspension is then filtered and then washed twice with 1 l of water. permutated water on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO,

The powder thus obtained has a specific surface area of 350 m ² / g, the sum of the mesoporous and microporous volumes is 0.20 cm / g and the powder is amorphous by X-ray diffraction. The ZHO particles are in a form needles of length L between 20 and 40 microns, width 1 between 2 and 5 microns, and thickness e between 1, 5 and 5 microns. For each of these needles, L / l is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1. The needles are similar to those of the starting ZBS derivative. The cake obtained is then dried in an oven for at least 12 hours at 110 ⁰ C, then spotted with agate mortar. The powder obtained was calcined in air for 2 hours (ramp 2 ° C / min, air flow rate of 100 ml / min, an hourly space velocity HSV of 300 ^{h -1)} at 500 ° C.

The powder thus obtained has a specific surface area of 100 m ² / g, the sum of the mesoporous and microporous volumes is 0.18 cm ² / g and the powder is crystallized under a mixture of quadratic and monoclinic phases determined by ray diffraction.

X. The zirconia particles are in the form of needles of length L between 15 and 30 microns, width 1 between 1 and 4 microns, and thickness e between 0.7 and 4 microns. For each of these needles, L / 1 is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1. The needles are similar to those of the ZBS derivative (shown in FIG. 3c) and ZHO initials. Example 4: Powder in the form of stars

In a Pyrex 1 1 beaker, 110 g of zirconium oxycholide are dissolved in 300 ml of deionized water at 50 ° C. and then 5 g of cetyltrimethylammonium bromide or CTAB are added, followed by 50 ml of acid. 36% hydrochloric acid HCl, then 28 g of sodium sulphate are added and the mixture is made up to 500 ml with deionized water. The temperature is adjusted to 50 ⁰ C and maintained for 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 2.4, the concentration of (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6 mol / l, the molar ratio between the anionic groups SO ₄ ^{2 "} and (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6, and the concentration of CTAB additive is 0.025 mol / 1. The presence of foam on the surface of the solution is observed.The solution is then brought, still with stirring, to 60 ^° C. with a heating ramp of 1 ° C / min, the solution is maintained at 60 ^° C. for 1 h and then allowed to cool freely to below 50 ^° C.

The ZBS powder thus obtained has a specific surface area of 3 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of stars of between 5 and 40 μm in length.

In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second 1 1 Teflon® PTFE beaker, 25 g of NaOH sodium hydroxide are dissolved in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ^° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5. by adding 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 11 by adding 1 N ammonia (NH ₄ OH). The suspension is then filtered and then washed twice with 1 l of water. permutated water on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO.

The powder thus obtained has a specific surface area of 340 m ² / g, the sum of the mesoporous and microporous volumes is 0.20 cm ³ / g and the powder is amorphous by X-ray diffraction. The ZHO particles are presented under the star shape of length between 5 and 40 microns, similar to those of the starting ZBS derivative.

The cake obtained is then dried in an oven for at least 12 hours at ^{0 °} C, and then stirred with agate mortar. The powder obtained is calcined under air for 2 hours (temperature ramp of 2 ° C./min, air flow rate of 100 ml / min, ie a VHV hourly volume velocity of 300 h ^-1 ) at 500 ° C. The powder thus obtained has a specific surface area of 90 m ² / g, the sum of the mesoporous and microporous volumes is 0.18 cm ³ / g and the powder is crystallized in the form of a mixture of quadratic and monoclinic phases determined by diffraction with X-rays. The zirconia particles are in the form of stars of between 5 and 30 μm in length, similar to that of the initial particles of the ZBS derivative (shown in FIG. 3d) and ZHO.

As shown in Figure 3d, the ZBS star forming needles have a tapered and pointed shape. These needles are substantially of revolution about their longitudinal axis. The surface of their cross section, substantially discoidal, decreases gradually as the tip (s). In addition, the lateral outer surface of the needles is particularly smooth. ZHO and zirconia needles have similar shapes.

Example 5: Powder in the form of sea urchins

In a beaker 1 1 Pyrex, are brought into solution at 5O ⁰ C with stirring 110 g of zirconium oxycholure in 300 ml of deionized water and then 0.5 g of cetyltrimethylammonium bromide or CTAB then added 28 g of sodium sulphate and complete with 500 ml of deionized water. The temperature is adjusted to 50 ⁰ C and maintained for 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 1.2, the concentration of (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6 mol / l, the molar ratio between the anionic groups SO ₄ ^{2 '} and (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6, and the concentration of CTAB additive is 0.0025 mol / l. The presence of foam on the surface of the solution is observed. The solution is then brought, still with stirring, to 60 ^° C. with a heating ramp of 1 ° C./min. The solution is maintained at 60 ^° C. for 1 h and then allowed to cool freely to below 50 ^° C.

The ZBS powder thus obtained has a specific surface area of 6 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of aggregates with a particle size of between 10 and 30 μm consisting of particles of length L of 2 μm in the form of needles and stars.

In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second 1 1 Teflon® PTFE beaker, 25 g of NaOH sodium hydroxide are dissolved in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ^° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water. on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 11 by adding 1 N ammonia (NH ₄ OH). The suspension is then filtered and then washed twice with 1 l of water. water swapped on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO.

The powder thus obtained has a specific surface area of 360 m ² / g, the sum of the mesoporous and microporous volumes is 0.25 cm ³ / g and the powder is amorphous by X-ray diffraction. The ZHO particles are presented under a form of aggregates whose largest dimension is between 10 and 30 microns, consisting of particles of 2 microns in the form of needles and stars, similar to those of the starting ZBS derivative.

The cake obtained is then dried in an oven for at least 12 hours at ^{0 °} C, and then stirred with agate mortar. The powder obtained was calcined in air for 2 hours (ramp 2 ° C / min, air flow rate of 100 ml / min, an hourly space velocity HSV of 300 h ^" ') at 500 ⁰ C.

The powder thus obtained has a specific surface area of 120 m ² / g, the sum of the mesoporous and microporous volumes is 0.21 cm ² / g and the powder is crystallized in the form of a mixture of quadratic and monoclinic phases determined by ray diffraction. X. The zirconia particles are in the form of aggregates whose largest dimension is between 5 and 20 μm, consisting of particles of 1 μm in the form of needles and stars, similar to those of initial particles of the derivative ZBS (shown in Figure 3e) and ZHO.

Example 6: Powder in the form of platelets

In a beaker 1 1 Pyrex, are brought into solution at 5O ⁰ C with stirring 110 g of zirconium oxycholure in 300 ml of deionized water and then 5 g of cétyltriméthylamrnonium bromide or CTAB then 25 ml of acid 36% hydrochloric acid HCl, then 28 g of sodium sulphate are added and the mixture is made up to 500 ml with deionized water. The temperature is adjusted to 50 ^° C. and maintained for 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 2, the concentration of (Zr ⁺ + Hf ⁴⁺ ) is 0.6 mol / l, the molar ratio between the anionic groups SO ₄ ^{2 *} and (Zr ⁴⁺ + Hf ^{4 +} ) is 0.6, and the concentration of CTAB additive is 0.025 mol / l. The presence of foam on the surface of the solution is observed. The solution is then brought, still with stirring, to 60 ^° C. with a heating ramp of 1 ° C./min. The solution is maintained at 60 ^° C. for 1 h and then allowed to cool freely to below 50 ^° C.

⁰ C.

The ZBS powder thus obtained has a specific surface area of 3 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of a mixture of approximately 50% of quasi-spherical particles. so-called "bunch of grapes" and 50% platelets with a thickness e of between 1 and 3 μm, of length L between 10 and 20 μm, and of width 1 between 10 and 15 μm. For each of these platelets, L / l is less than 1.5.

In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second 1 1 Teflon® PTFE beaker, 25 g of NaOH soda are dissolved in 250 ml of water. permuted water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water. on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 11 by adding 1 N ammonia (NH ₄ OH). The suspension is then filtered and then washed twice with 1 l of water. permutated water on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO. The powder thus obtained has a specific surface area of 340 m ² / g, the sum of the mesoporous and microporous volumes is 0.22 cm ³ / g and the powder is diffractionally amorphous The ZHO particles are in the form of a mixture of approximately 50% of particles of quasi-spherical shape called "bunch of grapes" and 50% of platelets with a thickness e of between 1 and 3 μm. , of length L between 10 and 20 microns, and width 1 between 10 and 15 microns, similar to those of the starting ZBS derivative. For each of these platelets, L / 1 is less than 1.5.

The cake obtained is then dried in an oven for at least 12 hours at 110 ⁰ C, then spotted with agate mortar. The powder obtained is calcined in air for 2 hours (temperature ramp of 2 ° C./min, air flow rate of 100 ml / min, ie a volume hourly velocity VVH of 300 h ^-1 ) at 500 ^° C. The powder thus obtained has a specific surface area of 80 m ² / g, the sum of the mesoporous and microporous volumes is 0.15 cm ³ / g and the powder is crystallized in the form of a mixture of quadratic and monoclinic phases determined by diffraction with X-rays. The zirconia particles are in the form of a mixture of about 50% of particles of quasi-spherical shape called "grape bunch" and 50% of platelets with a thickness e of between 1 and 2 μm. It has a length L between 8 and 15 μm, and a width 1 between 8 and 12 μm, which is similar to that of the initial particles of the ZBS derivative (represented in FIG. 3f) and of ZHO. L / l is less than 1.5.

EXAMPLE 7 Powder in the form of hollow particles In a Pyrex 1 1 beaker, 55 g of zirconium oxycholide are dissolved in 300 ml of deionized water at 50 ^° C. with stirring, then 2.5 g of cetyltrimethylammonium bromide or CTAB then 25 ml of 36% hydrochloric acid HCl, then 7 g of sodium sulfate and is added to 500 ml with deionized water, the temperature is adjusted to 50 ⁰ C and maintained during 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 1.2, the concentration of (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.3 mol / l, the molar ratio between the anionic groups SO ₄ ^" and (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.4, and the concentration of CTAB additive is 0.015 mol / l The presence of foam on the surface of the solution is observed The solution is then brought, still with stirring, at 60 ^° C. with a heating ramp of 1 ° C./min The solution is maintained at 60 ^° C. for 1 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant as well as foam. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake obtained consists of a basic zirconium sulfate, ZBS. The ZBS powder thus obtained has a specific surface area of 2 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of a mixture of approximately 50% quasi-spherical particles. so-called "bunch of grapes" and 50% of hollow particles, with a sphericity index between 0.85 and 0.9, with a larger outside diameter D of between 50 and 300 μm, and with a larger inside diameter D inclusive between 35 and 280 μm. The thickness of the wall of these spheres is between 5 and 20 microns, and the ratio D / D 'is less than 2.

In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second 1 1 Teflon® PTFE beaker, 25 g of NaOH sodium hydroxide are dissolved in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ^° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water. on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 1 1 by adding 1 N ammonia (NH ₄ OH). The suspension is then filtered and then washed twice with 1 l of water. permutated water on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO.

The powder thus obtained has a specific surface area of 280 m ² / g, the sum of the mesoporous and microporous volumes is 0.15 cm ³ / g and the powder is amorphous by X-ray diffraction. The ZHO particles are presented under the shape of a 50% mixture of particles of quasi-spherical shape called "grape bunch" and 50% of hollow particles, with a sphericity index between 0.85 and 0.9, with a larger outside diameter D of between 50 and 300 μm , and with a larger internal diameter D of between 35 and 280 μm. The thickness of the wall of these spheres is between 5 and 20 microns, and the D / D 'ratio is between 1.1 and 1.5. These forms are similar to those of the starting ZBS derivative.

The resulting cake is then dried in an oven for at least 12 hours at 110 C ^α and clods in agate mortar. The powder obtained is calcined under air for 2 hours (temperature ramp of 2 ° C./min, air flow rate of 100 ml / min, ie a hourly volume velocity VVH of 300 h ^-1 ) at 500 ^° C.

The powder thus obtained has a specific surface area of 60 m ² / g, the sum of the mesoporous and microporous volumes is 0.10 cm ³ / g and the powder is crystallized in the form of a mixture of quadratic and monoclinic phases determined by X-ray diffraction. The zirconia particles are in the form of a mixture of about 50% of particles of quasi-spherical shape called "bunch of grapes" and 50% of hollow particles, of sphericity index between 0.85 and 0.9, larger outside diameter D between 50 and 300 μm, and larger inside diameter D 'between 35 and 280 μm. The thickness of the wall of these spheres is between 5 and 20 microns, and the D / D 'ratio is between 1.1 and 1.5. This form is similar to that of the initial particles of the ZBS derivative (shown in Figure 3g) and ZHO.

Example 8: Powder in the form of lamellae

In a 1-liter Pyrex beaker, 110 g of zirconium oxycholide are dissolved in 300 ml of deionized water at a temperature of 50 ^° C., and then 100 g of cetyltrimethylammonium bromide (CTAB) are added and 28 of sodium sulphate and make up to 500 ml with deionized water. The temperature is adjusted to 50 ^° C. and maintained for 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 1, 2, the concentration of (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6 mol / l, the molar ratio between the anionic groups SO4 ^{2 "} and (Zr ⁴⁺ + Hf ⁴⁺ ) is 0.6, and the concentration of additive CTAB is 1 mol / 1. The presence of foam on the surface of the solution is observed.The solution is then brought, still with stirring, at 60 ^° C. with a heating ramp of 1 ° C / min. The solution is kept at 60 ° C. for 1 h and then allowed to cool freely to below 50 ^° C.

The ZBS powder thus obtained has a specific surface area of 4 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of a mixture of approximately 50% quasi-spherical particles. so-called "bunch of grapes" and 50% of platelets composed of 10 to 15 platelets of thickness e of 1 to 2 microns, length L between 10 and 20 microns, and width 1 between 10 and 15 microns. For each of these platelets, L / l is less than 1.5.

In a 1 1 Teflon® PTFE beaker, the cake is then suspended in 250 ml of deionized water. In a second beaker 1 liter Teflon® PTFE ₅ is dissolved 25 g of NaOH in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The suspension is then filtered and then washed with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 1 l of deionized water. on a Buchner type filter. The cake obtained is resuspended in 1 l of deionized water and the pH is adjusted to 1 liter by addition of ammonia (NH ₄ OH) to 1 N. The suspension is then filtered, then washed twice with 1 liter of permutated water on a Buchner type filter. The cake obtained is constituted by a zirconium hydrate, or ZHO. The powder thus obtained has a specific surface area of 340 m ² / g, the sum of the mesoporous and microporous volumes is 0.25 cm ² / g and the powder is amorphous by X-ray diffraction. The ZHO particles are in the form of a mixture of about 50% of particles of quasi-spherical shape called "bunch of grapes" and 50% of slats composed of 10 to 15 platelets thick e of 1 to 2 microns, length L between 10 and 20 microns, and width 1 between 10 and 15 microns, similar to those of the particles of the starting ZBS derivative. For each of these platelets, L / l is less than 1.5.

The cake obtained is then dried in an oven for at least 12 hours at 110 ⁰ C, then spotted with agate mortar. The powder obtained was calcined in air for 2 hours (ramp 2 ° C / min, air flow rate of 100 ml / min, an hourly space velocity HSV of 300 h ^"!) At 500 ° C.

The powder thus obtained has a specific surface area of 100 m ² / g, the sum of the mesoporous and microporous volumes is 0.20 cm ² / g and is crystallized in the form of a mixture of quadratic and monoclinic phases determined by X-ray diffraction. The zirconia particles are in the form of a mixture of approximately 50% of particles of quasi-spherical shape called "bunch of grapes" and 50% of slats composed of 10 to 15 plates of thickness e 0.5 at 1 μm, length L between 8 and 15 microns, and width 1 between 8 and 12 microns. This form is similar to that of the initial particles of the ZBS derivative and ZHO. For each of these platelets, L / 1 is less than 1.5.

Example 9: Powder in the form of needles, with a dopant introduced in the form of vttrium chloride YC13

In a 1 1 Teflon® PTFE beaker, 100 g of the ZBS of Example 3 is suspended in 250 ml of deionized water and then 80 g of yttrium chloride solution YC13 at 1 mol / l are added. (dopant type Dl). In a second 1 1 Teflon® PTFE beaker, 25 g of NaOH sodium hydroxide are dissolved in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ^° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid, then adjusted to 11 by adding ammonia (NH ₄ OH) to 1 N. The suspension is then filtered, then washed twice with 1 l of deionized water on a Buchner type filter. The cake obtained consists of a zirconium hydrate doped with an yttrium hydrate, or ZHY.

The main physicochemical properties of the powder thus obtained are given in Table Ib. This powder has a specific surface area of 300 m 2 / g, the sum of the mesoporous and microporous volumes of 0.18 cm 2 / g and is amorphous by diffraction. X-rays, ZHY particles are in the form of needles of length L ranging between 20 and 40 microns, width 1 between 2 and 5 microns, and thickness e between 1, 5 and 5 microns, similar to that of the starting ZBS derivative. For each of these needles, L / l is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1.

The cake obtained is then dried in an oven for at least 12 hours at 110 ⁰ C, then spotted with agate mortar. The powder obtained is calcined under air for 2 hours (temperature ramp of 2 ° C./min, air flow rate of 100 ml / min, ie a hourly volume velocity VVH of 300 h ^-1 ) at 800 ^° C.

The powder thus obtained has a specific surface area of 50 m ² / g, the sum of the mesoporous and microporous volumes is 0.15 cm ³ / g and the powder is crystallized in quadratic form determined by X-ray diffraction. The zirconia particles doped with 3 mol% of YiCh are in the form of needles of length L between 15 and 30 microns, width 1 between 1 and 4 microns, and thickness e between 0.7 and 4 microns, similar to the initial particles of the initial ZBS derivative and ZHY. For each of these needles, L / l is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1.

Example 10: Powder in the form of needles, with a dopant introduced in the form of yttrium chloride YCh

In a Teflon® PTFE 1 1 beaker, 100 g of the ZBS of Example 3 is suspended in 250 ml of deionized water, 220 g of yttrium chloride solution YCl ₃ at 1 mol / l are added. . In a second 1 1 Teflon® PTFE beaker, dissolve 25 g of sodium hydroxide in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ^° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 1 l of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid, then adjusted to 11 by adding ammonia (NH ₄ OH) to The suspension is then filtered and then washed twice with 1 l of deionized water on a Buchner type filter. The cake obtained consists of a zirconium hydrate doped with an yttrium hydrate, or ZHY.

The powder thus obtained has a specific surface area of 300 m ² / g, the sum of the mesoporous and microporous volumes is 0.15 cm ³ / g, and the powder is amorphous by X-ray diffraction. The particles of ZHY are presented under a shape of needles of length L between 20 and 40 microns, width 1 between 2 and 5 microns, and thickness e between 1.5 and 5 microns, similar to those of the starting ZBS derivative. For each of these needles, L / l is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1. The cake obtained is then dried in an oven for at least 12 hours at 1 10 ⁰ C, then spotted with agate mortar. The powder obtained is calcined in air for 2 hours (temperature ramp of 2 ° C./min, air flow rate of 100 ml / min, ie a hourly volume velocity VVH of 300 h ^-1 ) at 800 ^° C.

The powder thus obtained has a specific surface area of 45 m 2 / g, the sum of the mesoporous and microporous volumes is 0.13 cm ³ / g and the powder is crystallized in a cubic form determined by X-ray diffraction. The zirconia particles doped with 8 mol% of Y ₂ θ ₃ are in the form of needles of length L between

15 and 30 μm, width 1 between 1 and 4 microns, and thickness e between 0.7 and

4 .mu.m, similar to the initial particles of the initial derivative ZBS and ZHY. For each of these needles, L / l is between 1.67 and 50, and the thickness e is greater than 0.5 times the width 1. Example 11; Powder in the form of stars

In a Pyrex 11 beaker, 110 g of zirconium oxycholide are dissolved in 300 ml of deionized water at a temperature of 50 ^° C. and then 5 g of cetyltrimethylammonium bromide or CTAB and then 50 ml of hydrochloric acid are added. 36% HCl, then 28 g of sodium sulphate and is added to 500 ml with deionized water, the temperature is adjusted to 50 ⁰ C and maintained for 15 minutes after complete dissolution of the reagents. The acidity of the mother liquor is 2.4, the concentration of Zr ⁴⁺ ions and / or Hf ⁴⁺ is 0.6 mol / l, the molar ratio between the anionic groups SO ₄ ^{2 "} and the Zr ions ⁴⁺ and / or Hf ⁴⁺ is 0.6, and the concentration of CTAB additive is 0.025 mol / 1. The presence of foam on the surface of the mother liquor is observed.The mother liquor is then brought, still stirring. at 60 ° C. with a heating ramp of 1 ° C./min The mother liquor is maintained at 60 ^° C. for 1 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant, and the foam The suspension is then filtered and then washed with 11 of permutated water on a Buchner type filter The cake obtained consists of a basic zirconium sulfate, ZBS .

The main physico-chemical properties of the ZBS powder thus obtained are given in the following tables. This powder has a specific surface area of 3 m ² / g and is amorphous by X-ray diffraction. The ZBS particles are in the form of stars whose largest dimension is between 5 and 40 μm.

In a Teflon® PTFE 11 beaker, the cake is then suspended in 250 ml of deionized water. In a second beaker of Teflon PTFE, 25 g of NaOH sodium hydroxide are dissolved in 250 ml of deionized water. The basic solution of sodium hydroxide is then gradually added to the suspension of ZBS; the pH of the final suspension is between 12 and 13. The suspension is then heated to 90 ^° C. with a heating ramp of 1 ° C./min. The suspension is maintained at 90 ^° C. for 2 h and then allowed to cool freely to below 50 ^° C. This procedure generates a suspension consisting of a solid phase and a liquid supernatant. The suspension is then filtered and then washed twice with 11 of deionized water on a Buchner type filter. The suspension is then filtered, then washed with 11 of deionized water on a Buchner type filter. The cake thus obtained is then resuspended in 11 of deionized water and the pH is adjusted to 5 by addition of 0.1 N hydrochloric acid. The suspension is then filtered and then washed with 11% of deionized water on a Buchner type filter. The cake obtained is resuspended in 11 of deionized water and the pH is adjusted to 11 by adding ammonia (NH 4 OH) to 1 N. The suspension is then filtered, then washed twice with 11 of deionized water on a Buchner type filter. The cake obtained consists of a zirconium oxyhydroxide, or ZHO.

The powder thus obtained has a specific surface area of 340 m ² / g, the sum of the mesoporous and microporous volumes of 0.20 cm ³ / g and the powder is amorphous by X-ray diffraction. The ZHO particles are in the form of stars whose largest dimension is between 5 and 40 microns, similar to those of the ZBS derivative of departure.

The cake obtained is then dried in an oven for at least 12 hours at 110 ⁰ C, then spotted with agate mortar. The powder obtained is calcined in air for 2 hours (temperature ramp of 5 ° C./min, without air flow) at 1250 ° C.

The powder thus obtained has a specific surface area of 2 m ² / g, the sum of the mesoporous and microporous volumes equal to 0.01 cm ³ / g and the powder is crystallized under the monoclinic phase determined by X-ray diffraction. zirconia are in the form of stars whose largest dimension is between 5 and 30 microns, similar to those of the derivative ZBS (shown in Figure 3h) and hydrate ZHO initial.

As shown in FIG. 3h, the needles forming the zirconia stars have a tapered, rectilinear and pointed shape. These needles are substantially of revolution about their longitudinal axis. The surface of their cross section, substantially discoidal, decreases gradually as the tip (s). In addition, the lateral outer surface of the needles is particularly smooth.

The following tables specify the compositions of the examples manufactured, as well as their loss on ignition.

The following tables provide the results of measurements made on the particles of the examples.

"P" is the sum of the mesoporous volume and the microporous volume.

Dpores is the average equivalent diameter of pores less than 50 nm in size.

"Mono" refers to the monoclinic phase.

"Quadra" refers to the quadratic phase.

"Cub" refers to the cubic phase

As now clearly apparent, the invention makes it possible to manufacture new anisotropic particles or particles consisting of anisotropic base particles which, advantageously, make it possible to create a body or a powder having a high porosity. Such bodies and powders are particularly useful in applications to catalysis or filtration.

In addition, these anisotropic particles or particles consisting of anisotropic base particles may themselves be of a porous material, and in particular may have microporosity and / or mesoporosity. These microporosity and / or mesoporosity are

10 in particular exploitable for the catalysis of certain chemical reactions.

Claims

1. Powder having a maximum particle size D _{9915 of} less than 200 μm and having a porosity index Ip of greater than 2, the porosity index being equal to the ratio A _sr / A _sg where o A _sg is the specific surface area theoretical geometry of the particles of the powder; o A _sr is the measurement of the actual specific area by BET, and / or - when all the dimensions of the basic particles of the powder are greater than 50nm, a specific surface area greater than 10mVg and a sum of upper mesoporous and microporous volumes at 0.05 cm ³ / g, said powder comprising more than 20% by number of basic particles, aggregated or not, all dimensions of which are greater than 200 nm, having a sphericity index of less than 0.6, and constituted in a zirconium and / or hafnium oxide of formula MO _x , M being Zr ⁴⁺ , Hf ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , and x being a non-zero positive number.

2. Powder according to the preceding claim, comprising more than 90% by number of said basic particles.

The powder of any preceding claim, wherein said base particles have a sphericity index greater than 0.02.

4. Powder according to the preceding claim, wherein said base particles have a sphericity index greater than 0.1 and less than 0.3.

5. A powder according to any preceding claim, having a surface area greater than 50 m ^z / g and a sum of mesopore and micropore volumes of greater than 0.10 cm / g.

6. Powder according to the preceding claim, having a specific surface area greater than 100 mVg and a sum of mesoporous and microporous volumes greater than 0.10 cm ³ / g.

A powder according to any one of the preceding claims, wherein at least 80% by number of said base particles are needle and / or wafer shaped.

8. Powder according to the preceding claim, wherein at least 80% by number of said base particles are assembled in the form of aggregated ordered and / or disordered particles.

9. Powder according to the preceding claim, wherein said aggregated particles are in the form of stars having 3 to 15 branches.

The powder of claim 8, wherein said aggregated particles are in the form of lamellae consisting of 2 to 50 platelets.

The powder of claim 8, wherein said aggregated particles are in the form of hollow spheres having a sphericity index greater than 0.7 and having a central cavity such that, if D is the largest outer diameter of the particle and D 'denotes the largest inside diameter of the cavity, D / D' <2.

Powder according to any one of the preceding claims, wherein all the dimensions of the base particles are greater than 200 nm.

13. Powder according to any one of the preceding claims, having a maximum particle size DMs less than 150 microns.

14. Powder according to any one of the preceding claims, said oxide being doped by means of a dopant chosen from the compounds of elements of column 17, the compounds of elements of column 1, yttrium compounds Y , scandium Sc, lanthanides, alkaline earth, titanium Ti, silicon If, sulfur S ₅ phosphorus P, aluminum Al, tungsten W, chromium Cr, molybdenum Mo, vanadium V , antimony Sb, nickel Ni, copper Cu, zinc Zn, iron Fe ₅ manganese Mn, niobium Nb, gallium Ga, tin Sn, lead Pb, cobalt Co, ruthenium Ru , rhodium Rh, palladium Pd and silver Ag ₅ osmium Os, iridium Ir, Pt platinum, gold Au, and mixtures thereof.

15. Powder according to the preceding claim, said oxide, called "first oxide", being doped by means of a dopant chosen from: a second oxide of an element chosen from Y, La, Ce, Sc, Ca, Mg and their mixtures, in solid solution with said first oxide;

- a second oxide of an element selected from Si, AI ₅ O and mixtures thereof dispersed in said first oxide; - and their mixtures.

16. Powder according to any one of the two immediately preceding claims, the molar amount of dopant being less than or equal to 20%.

17. Powder according to any one of the preceding claims, the particles having a shape different from that of a wafer, a needle or a coverslip.

18. Powder having a maximum particle size of 0 _99.5 less than 200 μm, a specific surface area of less than 10 μm and a sum of mesoporous and microporous volumes of less than 0.05 cm ³ / g, all the dimensions of the basic particles constituting said powder being greater than 50 nm, said powder comprising more than 20% by number of base particles having a sphericity index of less than 0.6, aggregated in the form of stars comprising from 3 to 15 tapered and / or rectilinear branches or platelets consisting of 2 to 50 platelets, and consisting of a zirconium and / or hafhium oxide of formula MO _x , M being Zr ⁴⁺ , Hf ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , and x being a non-zero positive number.

19. Powder having a maximum particle size D _{9915 of} less than 200 μm, a specific surface area of less than 10 μm and a sum of mesoporous and microporous volumes of less than 0.05 cm ³ / g, all the dimensions of the basic particles of said powder being greater than 50 nm, said powder comprising more than 20% by number of base particles having a sphericity index of less than 0.6, and consisting of a zirconium and / or hafnium oxide of formula MO _x , M being Zr ⁴⁺ , Hf ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , and x being a nonzero positive number, said oxide, called "first oxide", being doped by means of a dopant chosen from: a second oxide of an element chosen from Y, La, Ce, Sc, Ca, Mg and their mixtures, in solid solution with said first oxide;

a second oxide of an element chosen from Si, Al, S and their mixtures dispersed in said first oxide; - and their mixtures.

20. Powder according to the preceding claim, wherein said base particles are in the form of platelets and / or are aggregated in the form of stars and / or lamellae and / or sea urchins and / or hollow spheres.

21. Powder according to any one of the two immediately preceding claims, wherein all the dimensions of the base particles are greater than 200 nm.

22. A process for producing a powder of particles of zirconium oxides and / or hafnium, doped or not, comprising a step of calcination (eθ) or hydrothermal treatment (e ₂ )) of a particle powder starting material, consisting of base particles, aggregated or not, said base particles having a sphericity index of less than 0.6, said starting particles being of a material selected from

the zirconium and / or hafnium derivatives of formula M (OH) _x (N ') _y (OH 2) _z , M being Zr ⁴⁺ , Hf ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , N 'being an anion or a mixture of anions, the indices x and y being strictly positive numbers, z being a positive or zero number, said material having a solubility in water at a temperature below 20 ^° C. 10 ^"3 mol / 1, said derivative being dopable or not,

the hydrates of zirconium and / or of hafnium of formula MO _x (OH) _y (OH 2) _z , M being Zr ⁴⁺ , Hr ⁴⁺ , or a mixture of Zr ⁴⁺ and Hf ⁴⁺ , the indices x and z being positive or zero numbers, the index y being a positive number, and 2x + y being equal to 4, doped or not, or a mixture of such hydrates, doped or not, and

their mixtures, or a mixture of these particles, and when said starting particles are in a hydrate, said starting particle powder having a porosity index Ip greater than 2, the porosity index being equal to the ratio A _sr / A _sg where o A _sg is the theoretical geometric specific surface area of the particles of the powder; o A _sr is the measurement of the actual specific area by BET, and / or

a specific surface area greater than 10 m ² / g and a sum of mesoporous and microporous volumes greater than 0.05 cm / g, all the dimensions of said base particles being greater than 50 nm.

23. Method according to the preceding claim, wherein said material is selected from basic zirconium sulfate and / or hafnium, doped or not, the basic phosphate of zirconium and / or hafnium doped or not, the basic carbonate of zirconium and / or hafnium doped or not, and mixtures thereof.

24. Device selected from a catalyst, a catalyst support, a filter element, a fuel cell element, a piezoelectric material, an optical connector, a dental ceramic, a structural ceramic, comprising or obtained (e) from a powder according to any one of claims 1 to

21.