Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/0004—Preparation of sols
  • B01J13/0008—Sols of inorganic materials in water
  • B01J13/0013—Sols of inorganic materials in water from a precipitate
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B35/00—Boron; Compounds thereof
  • C01B35/08—Compounds containing boron and nitrogen, phosphorus, oxygen, sulfur, selenium or tellurium
  • C01B35/10—Compounds containing boron and oxygen
  • C01B35/12—Borates
  • C01B35/127—Borates of heavy metals
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B35/00—Boron; Compounds thereof
  • C01B35/08—Compounds containing boron and nitrogen, phosphorus, oxygen, sulfur, selenium or tellurium
  • C01B35/10—Compounds containing boron and oxygen
  • C01B35/12—Borates
  • C01B35/128—Borates containing plural metal or metal and ammonium
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
  • C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
  • C09K11/778—Borates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
  • C09K11/7783—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals one of which being europium
  • C09K11/7797—Borates

Definitions

• the present invention relates to a colloidal dispersion of a rare earth borate, its method of preparation and its use as a phosphor.
• these materials are required to have specific characteristics of morphology or granulometry, in particular to facilitate their implementation in the desired applications.
• luminophores in the form of particles as much as possible individualized and very fine size.
• Soils or colloidal dispersions can be an interesting way to access such a type of product.
• the object of the invention is to provide a rare earth borate in the form of a colloidal dispersion.
• the colloidal dispersion of rare earth borate according to the invention is characterized in that it comprises a liquid phase and colloids of said borate in dispersion in this phase, these colloids having a mean hydrodynamic diameter measured by DQEL of at most 200 nm and consisting substantially of an elementary particle of average size less than 100 nm.
• the invention also relates to a process for preparing this dispersion which is characterized in that it comprises the following steps: (a) reacting a rare earth oxide with a controlled amount of a monovalent acid, soluble in water and having a pka of 2.5 to 5.0; (b) the medium obtained is heated at the end of the reaction; (c) adding boric acid to the medium obtained at the end of the preceding step and heating the mixture obtained to a temperature of at least 170 ° C .;
• FIG. 1 is an RX diagram of a product according to the invention.
• FIG. 2 is a transmission electron microscopy (TEM) photograph of this same product
• FIG. 3 is a transmission electron microscopy (TEM) photo of another product according to the invention.
• rare earth is understood to mean the elements of the group consisting of scandium, yttrium and the elements of the periodic classification of atomic number inclusive of between 57 and 71.
• colloidal dispersion or soil of a rare earth borate designates any system consisting of colloids of this compound, ie particles whose size is generally at most about 200 nm. (average size determined by quasi-elastic light scattering (DQEL)).
• colloids are in stable suspension in a liquid continuous phase, said colloids may contain, as counter-ions, bound or adsorbed ions such as, for example, acetates, nitrates, chlorides or ammoniums.
• the borate may be either completely in the form of colloids, or simultaneously in the form of ions or polyions and in the form of colloids.
• the rare earth borate of the invention is of the orthoborate type, of formula LnB ⁇ 3, Ln representing at least one rare earth. It is emphasized here that the invention applies to borates of one or more rare earths. Therefore, throughout the description, all that is described about a rare earth borate and its process of preparation should be understood as also applying to the case where several rare earths are presented.
• the rare earth constitutive of the borate of the invention that is to say the one which forms with boron the matrix of the product preferably belongs to the group of rare earths which do not have a luminescence property.
• this constitutive rare earth borate can be chosen, alone or in combination, in the group comprising yttrium, gadolinium, lanthanum, lutetium and scandium. It may be more particularly yttrium and / or gadolinium.
• the borate may further comprise one or more dopants.
• the dopants are used in combination with the matrix to give it luminescence properties.
• These dopants can be chosen from antimony, bismuth and rare earths.
• the rare earth or rare earths used as dopant are chosen from the group of rare earths with luminescence properties and they are different from the rare earth constitutive of the borate.
• doping rare earth mention may be made of cerium, terbium, europium, dysprosium, holmium, ytterbium, neodymium, thulium, erbium and praseodymium. Terbium, thulium, cerium and europium are more particularly used.
• the dopant content is usually at most 50 mol% relative to the rare earth borate matrix ([dopant] / [ ⁇ Ln] ratio), ⁇ Ln representing the rare earth and dopant set in the borate.
• boron borate of the invention may be partially substituted by aluminum in an Al / B atomic ratio of up to 20%.
• the colloids constituting the dispersion of the invention may have a size of at most about 200 nm (average hydrodynamic diameter measured by DQEL), this size may be more particularly at most 150 nm and even more particularly at most
• the colloids of the dispersion consist of elementary particles whose average size is less than 100 nm.
• the average size of the elementary particles is at most 70 nm and can be even more particularly at most 60 nm.
• this size may be between 5 and 100 nm, this latter value being excluded, more particularly between 10 nm and 70 nm and even more particularly between 20 nm and 60 nm. It should be noted that below 5 nm, the interest of the product in the field of luminescence may be less important.
• the average size of the elementary particles is measured using the X-ray diffraction (XRD) technique, this measurement possibly being completed by a MET measurement as indicated below.
• XRD X-ray diffraction
• elementary particle is meant a particle which is not itself composed of an agglomerate of other smaller particles or else which can not be broken down into smaller particles simply by deagglomeration.
• elementary aspect of a particle can also be demonstrated by comparing the mean particle size measured by the TEM technique with the value of the measurement of the crystal size or the coherent domain obtained from the XRD analysis. It is specified here that the value measured in DRX corresponds to the size of the coherent domain calculated from the width of the two most intense diffraction lines.
• the Scherrer model as described in the book Theory and Technique of Radiocrystallography, A.Guinier, Dunod, Paris, 1956, is used for this measurement.
• diffraction lines corresponding to the (1 0 0) and (1 0 2) planes For example, in the case of YBO 3 , diffraction lines corresponding to the (1 0 0) and (1 0 2) planes.
• the two values: average size determined by MET (ti) and average size determined by DRX (t 2 ) have, for the elementary particles of the invention, the same order of magnitude, that is to say, in the sense of the present description, that they are in a ratio Vt 2 of at most 3, more particularly at most 2.
• the borate colloids of the invention consist substantially of an elementary particle. By this is meant that they are in a well separated and individualized form, the bulk of the colloids, preferably the whole, being thus constituted of a single elementary particle. However, there may be some agglomeration rate of the elementary particles.
• the colloids consist of elementary particles by comparing the average hydrodynamic diameter of the colloids measured by DQEL (di) and the average size of the aforementioned elementary particles (ti) determined by (MET).
• the values obtained by these two techniques have the same order of magnitude, ie, in the sense of the present description, that they are in a ratio di / ti of at most 4, more particularly of at most 3. It is specified here that the measurements by DQEL (Malvern apparatus) are made on the dispersion as it is, possibly diluted in water, but without dispersant type additive and without ultrasound treatment.
• the size distribution is given in intensity, according to a monomodal model, with a refractive index of particles in suspension of 1, 8.
• the colloids constituting the dispersion are monodisperse.
• This monodispersity is characterized by a colloid polydispersity index measured by DQEL which is at most 0.6, preferably at most 0.5 and even more preferably at most 0.4.
• the elementary particles which constitute the colloids are in the form of a pure phase.
• the particle X-ray diagram shows only one crystallographic phase which is that corresponding to LnB ⁇ 3.
• the X-ray diagram thus does not reveal parasitic phases such as oxides or hydroxides.
• the liquid phase of the suspensions according to the invention is generally water but it can also be a mixture of water / solvent miscible with water or an organic solvent.
• the organic solvent may be very particularly a solvent miscible with water.
• alcohols such as methanol or ethanol
• glycols such as ethylene glycol
• acetate derivatives of glycols such as ethylene glycol monoacetate
• glycol ethers such as glycol ethers, polyols or ketones.
• the liquid phase may also include a complexing agent. This is the case more particularly for aqueous dispersions intended to be transferred into an organic liquid phase or for dispersions in the organic liquid phase.
• This complexing agent may be chosen from known complexing agents, for example from polyphosphates (M n + 2 P n O 3n + -I) or metaphosphates ([MPO 3 ] n) which are alkaline (M denotes an alkaline such as sodium), especially as sodium hexametaphosphate. It can also be chosen from alkali silicates (sodium silicate), amino alcohols, phosphonates, citric acid and its salts, phosphosuccinic acid derivatives ((HOOC) n -R-PO 3 H 2 where R is an alkyl radical), polyacrylic acid, polymethacrylic acid, polystyrene sulphonic acid and salts thereof. Citric acid and metaphosphates are particularly preferred.
• the amount of complexing agent may be between 0.1% and 10%, more particularly between 2.5% and 5%, this amount being expressed as the weight of complexing agent relative to the mass of solid in the dispersion.
• the concentration of the dispersion may be for example between about 10 g / l and about 100 g / l, this concentration being expressed in grams of rare earth borate and given for information only.
• the dispersion of the invention is stable for at least 1 month, ie no decantation is observed after this time.
• the invention also relates to a borate which is in solid form, that is to say a powder and which can be obtained by drying the dispersion as described above.
• This powder has the property of being redispersible that is to say to be redispersed in water so that after release into the water, and possibly a slight treatment with ultrasound, for example 5 minutes at low power (100W), a colloidal dispersion is obtained having all the characteristics which have been described above (size of the elementary particles in particular).
• This process comprises a first step, step (a), in which a rare earth oxide is reacted with a specific acid.
• a rare earth oxide is reacted with a specific acid.
• the oxide used is of high purity, preferably greater than or equal to 99% and, more preferably, an oxide having a purity of 99.99% is used.
• the rare earth oxide is generally in the form of a fine powder whose particle size is a few microns and whose average diameter is, usually between 1 and 5 microns (laser granulometry).
• the mean diameter is defined here as a diameter such that 50% by weight of the particles have a diameter greater than or less than the average diameter.
• a preferred variant of the process of the invention consists in using a rare earth oxide having undergone calcination at a temperature of between 850 ° C. and 1050 ° C.
• the calcination time is preferably between 2 and 4 hours.
• Acetic acid is quite suitable for carrying out the process of the invention. It is preferable to use an acid free of impurities. Its initial concentration is not critical and it can be used diluted, for example, 1 N or concentrated up to 17 N. Generally, the concentration of the solution of said acid is chosen between 1 and 4N because it constitutes the dispersion medium rare earth oxide and must therefore constitute a liquid phase sufficiently large to allow the attack to be carried out under good stirring conditions.
• the amount of acid used is an important part of the process of the invention. It must be in default with respect to stoichiometry, which means that the molar ratio between the acid used and the rare earth oxide (or all of the rare earth oxides in the case of borates comprising several rare earth elements The lower limit is defined with regard to the economic requirements of good reaction efficiency and good reaction kinetics. In a preferential manner, said molar ratio is chosen between 1, 1 and 2.2 and, preferably, between 1, 2 and 1, 8.
• the rare earth oxide is added to the solution of the acid whose concentration is adjusted so that it corresponds to what is indicated above.
• the rare earth oxide is suspended in water and the acid is then added in an adequate amount. This operation is carried out in both cases with stirring and at a temperature which can be ambient (15 0 C - 25 ° C) or a higher temperature.
• the second step (step b) of the process of the invention consists in subjecting the medium resulting from step (a) to heating.
• This heating is generally at a temperature which is between 50 ° C and the reflux temperature of the reaction medium.
• the heat treatment is carried out between 70 ° C and 100 ° C. The duration of said treatment is very variable and will be even shorter as the temperature is high. Once the reaction temperature is reached, it is maintained for 1 to 4 hours and preferably for 3 to 4 hours.
• step c of the process of the invention is added boric acid to the medium obtained at the end of the previous step.
• This acid is added in an amount which can vary over a wide range, preferably in an amount such that the molar ratio B / Ln is between 0.9 and 2, because, in this case, the borate is optimally obtained in the form of a pure phase.
• the mixture thus formed is then heated to a temperature of at least 170 ° C, preferably 180 ° C to 200 ° C.
• a temperature of at least 180 ° C easily leads to a well crystallized product.
• Below 170 ° C the borate may be amorphous.
• the heating operation is conducted by introducing the liquid medium into a closed chamber (autoclave type closed reactor), preferably equipped with a stirring system.
• the heating can be conducted either under air or under an inert gas atmosphere, preferably N 2 .
• the duration of the heating is not critical, and can thus vary within wide limits, for example between 1 and 48 hours, preferably between 2 and 24 hours.
• the rise in temperature is carried out at a speed which is not critical, and it is thus possible to reach the reaction temperature set by heating the medium for example between 30 minutes and 4 hours, these values being given for all purposes. indicative, it being understood that it is necessary to heat over a time and at a temperature sufficient to form the desired orthoborate phase.
• step d the solid product is separated from the liquid medium obtained at the end of the heating of step (c). This separation is done according to the known techniques of solid-liquid separation: filtration, decantation or centrifugation preferably.
• the product thus separated can be optionally washed. It is thus possible to make two successive solid-liquid separations and to wash the separated product resulting from the first separation by redispersing it in water.
• this complexing agent can be added at the time of washing.
• the product is finally redispersed in water with possibly a light treatment with ultrasound, for example 5 minutes at low power (100W).
• a light treatment with ultrasound for example 5 minutes at low power (100W).
• the re-dispersion is done in water at neutral pH, and a dispersion according to the invention is thus obtained.
• this dispersion can be prepared from an aqueous dispersion as obtained by the process just described and by addition of the organic solvent. of the type mentioned above to this aqueous dispersion and then distillation to remove water.
• the description which has just been made concerns the preparation of the borate in the form of a colloidal dispersion.
• this dispersion is dispersed and dried by any known means, preferably at a rather low temperature, that is to say not more than 120.degree. C, in an oven for example.
• the solid product thus obtained can be resuspended in water to give a colloidal dispersion according to the invention as indicated above.
• the borates of the invention are understood to mean here and for the rest of the description, the borates in the form of a colloidal dispersion or the borates in solid form or the borates obtained by the method of preparation which has been described above, can be used directly or not (that is to say in the latter case after a heat treatment) as phosphors.
• borates exhibit luminescence properties under electromagnetic excitation in the wavelength range used in plasma systems (screens and lamps where the excitation is created by a rare gas or a mixture of noble gases such as xenon and / or and neon) and in mercury vapor lamps in the case of borates doped with cerium and terbium in combination. Therefore, they can be used as phosphors in plasma systems (display screen or lighting system) or in mercury vapor lamps. In the particular case of borates doped with cerium and terbium, these products can also be used as luminophores in UV-emitting light-emitting diodes.
• the invention therefore also relates to luminescent devices, in particular comprising the borate of the invention, as defined in the preceding paragraph, or devices manufactured using this same borate.
• the invention relates to plasma systems, mercury vapor lamps or light emitting diodes, in the manufacture of which the borate can enter, or comprising the same borate.
• the use of phosphors in the manufacture of plasma systems is done according to well-known techniques, for example by screen printing, electrophoresis or sedimentation.
• the particle size properties of borates of the invention are that they can be used as markers in transparent inks using the mechanisms by addition of photons (up-conversion) in I 1 I R- Visible luminescence or in the IR, for example for carrying out a marking by an invisible bar code system.
• the pair of dopants will preferably be Yb and Er. Similar use but using UV excitation is also possible with thulium or the cerium / terbium pair as the dopant.
• the borates of the invention can also be used as markers in a material such as paper, cardboard, textile, glass or a macromolecular material. This can be of different types: elastomeric, thermoplastic, thermosetting.
• these borates when they are not doped, in the visible range and UV (no absorption), make them suitable for use as a reflecting barrier in system lighting lamps. mercury vapor or plasma.
• the invention also relates to a luminescent material which comprises or may be manufactured using at least one borate according to the invention, that is to say again in the form of a colloidal dispersion or in solid form or else obtained by the method of preparation described above. According to a preferred embodiment, this luminescent material may be furthermore transparent.
• this material may comprise, or be manufactured using, in addition to the borate of the invention, other borates, or more generally, other luminophores, in the form of submicron or nanometric particles.
• This material can be in two forms, that is to say either in a mass form, the whole of the material having the properties of transparency and luminescence is in a composite form, that is to say in this case in the form of a substrate and a layer on this substrate, the layer then only having these properties of transparency and luminescence.
• the borate of the invention is contained in said layer.
• the substrate of the material is a substrate which may be silicon, silicone-based or quartz-based. It can also be a glass or a polymer such as polycarbonate.
• the substrate, for example the polymer may be in a rigid form and a sheet or plate a few millimeters thick. It can also be in the form of a film of a few tens of microns or even a few microns to a few tenths of a millimeter thick.
• the term "transparent material” means a material which has a haze of at most 50% and a total transmission of at least 60% and preferably a haze of at most 30% and a total transmission of at least 80% and, even more preferentially, a disturbance of not more than 20% and a total transmission of at least 85%.
• the total transmission is the amount of total light that passes through the layer, relative to the amount of incident light.
• the haze corresponds to the ratio of the diffuse transmission of the layer to its total transmission.
• the layer of material with a thickness of between 0.2 ⁇ m and 1 ⁇ m is deposited on a standard glass substrate, 0.5 mm thick.
• the mass fraction of borate particles in the material is at least 20%.
• the total transmission and diffuse transmission measurements are made through the material and substrate layer, using a standard procedure on a Perkin Elmer Lamda 900 spectrometer, equipped with an integrating sphere, for a wavelength of 550 nm.
• the material may comprise, besides a borate according to the invention, binders or fillers of the polymer (polycarbonate, methacrylate), silicate, silica ball, phosphate, titanium oxide or other mineral fillers type. to improve in particular the mechanical and optical properties of the material.
• binders or fillers of the polymer polycarbonate, methacrylate
• silicate silica ball
• phosphate titanium oxide
• titanium oxide titanium oxide
• the mass fraction of borate particles in the material may be between 20% and 99%.
• the thickness of the layer may be between 30 nm and 10 ⁇ m, preferably between 100 nm and 3 ⁇ m and even more preferably between 100 nm and 1 ⁇ m.
• the material, in its composite form, can be obtained by depositing on the substrate, optionally previously washed for example with a sulpho-chromic mixture or subjected beforehand to a plasma hydrophilizing treatment, a borate dispersion of the invention. It is also possible to add at the time of this deposit, binders or charges mentioned above. This deposit can be achieved by a spraying technique, "spin-coating” or "dip-coating". After deposition of the layer, the substrate is dried in air and it can optionally subsequently undergo a heat treatment. The heat treatment is carried out by heating to a temperature which is generally at least 200 ° C. and the higher value of which is fixed in particular taking into account the compatibility of the layer with the substrate so as to avoid interfering reactions in particular.
• the drying and the heat treatment can be conducted under air, under an inert atmosphere, under vacuum or under hydrogen.
• the material may comprise binders or fillers. It is possible in this case to use suspensions which themselves comprise at least one of these binders or these fillers or precursors thereof.
• the material in the mass form can be obtained by incorporating the borate particles in a polymer type matrix for example, such as polycarbonate, polymethacrylate or silicone.
• the invention relates to a luminescent system which comprises a material of the type described above and, in addition, an excitation source which may be a source of UV photons, such as a UV diode or an excitation of the Hg gas type. rare or X-rays.
• an excitation source which may be a source of UV photons, such as a UV diode or an excitation of the Hg gas type. rare or X-rays.
• the system can be used as a transparent wall lighting device, of the illuminating glazing type.
• This example relates to yttrium and europium borate, (Y 1 Eu) BO 3 , which is a red phosphor.
• the colloidal dispersion obtained is highly luminescent in the orange-red under UV and VUV excitation.
• the size of the crystallites measured by Scherrer's law, is 31 nm for the diffraction line corresponding to the plane (1 0 2) and 37 nm for the diffraction line corresponding to the (1 0 0) plane.
• the TEM microscopy shows the presence of particles of average size (in number) of 50 nm.
• This example relates to an yttrium and terbium borate, (Y 1 Tb) BO 3 , which is a green phosphor.
• the X-ray diffraction carried out on the oven-dried product at 60 ° C. shows that the product consists of a pure phase of YBO 3 type.
• the size of the crystallites, measured by Scherrer's law, is 22 nm for the diffraction line corresponding to the plane (1 0 2) and 31 nm for the diffraction line corresponding to the (1 0 0) plane.
• the TEM microscopy (FIG. 3) shows the presence of particles of average size (in number) of approximately 50 nm.
• EXAMPLE 3 This example relates to yttrium, gadolinium and terbium borate,
• the mixture is autoclaved and brought to 200 ° C for 17h. At the end of this treatment, the product is then washed with water by centrifugation and resuspended in water.
• the colloidal dispersion according to the invention is then obtained.
• the colloidal dispersion obtained is highly luminescent in the green under UV and VUV excitation.
• the X-ray diffraction carried out on the oven-dried product at 60 ° C. shows that the product consists of a pure phase of YBO 3 type.
• the size of the crystallites, measured by Scherrer's law, is 38 nm for the diffraction line corresponding to the (1 0 2) plane and 43 nm for the diffraction line corresponding to the (1 0 0) plane.
• the TEM microscopy picture shows the presence of particles of average size (in number) of about 50 nm.
• EXAMPLE 4 This example relates to yttrium and thulium borate, (Y 1 Tm) BO 3 .
• the X-ray diffraction carried out on the oven-dried product at 60 ° C. shows that the product consists of a pure phase of YBO 3 type. Size crystallites, measured by Scherrer's law, is 31 nm for the diffraction line corresponding to the plane (1 0 2) and 43 nm for the diffraction line corresponding to the (1 0 0) plane.
• the TEM microscopy picture shows the presence of particles of average size (in number) of about 50 nm.
• This example concerns the production of a nanocomposite transparent and luminescent thin film based on nanoparticles of (Y 1 Eu) BO 3 and silica.
• the dispersion of Example 1 (3 mL at 30 g / L) is mixed with a solution of 10% by weight of lithium polysilicate in solution in water in proportions such that the silicate / borate ratio is 10% by mass. .
• the mixture is deposited on a previously hydrophilized glass substrate (plasma treatment of 30 seconds) by spin-coating (1900 rpm for 65 seconds).
• the film is then dried for 1 h at 120 ° C. in an oven. Two successive deposits are made.
• the thickness of the layer after deposition is about 300 nm.
• a film transparent and luminescent to the eye under UV excitation is obtained.
• the film has a total transmission of 90.6% and a haze of 3% at 550 nm (values measured under the conditions described above).
• the film luminesce in the red under UV excitation (230 nm) and VUV (172 nm).
• the brightness and the transparency of the films are not impaired after thermal aftertreatment (at 450 ° C. for 1 hour), as well as under UV irradiation (24h at 230 nm).

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