JPS6227328A - Production of easily sinterable powdery starting material for perovskite and its solid solution - Google Patents

Abstract

PURPOSE:To obtain a product having sinterability, uniformity and high bulk density at a low cost when a powdery starting material for perovskite contg. oxygen 12 and 6 coordinating metallic elements and a solid soln. thereof is produced by a wet process, by successively forming precipitates of the constituents. CONSTITUTION:When a powdery starting material for perovskite represented by the general formula (where A and B are one or more kinds of metallic elements coordinating oxygen 12 and 6) and a solid soln. thereof is produced, one or more kinds of aqueous solns. of compounds each contg. metallic elements A and/or B are prepd. An aqueous soln. of a compound contg. the remaining metallic element is further prepd. Those solns. are successively added to a precipitate forming soln. to form precipitates. The resulting slurry is heated at 130-300 deg.C to separate the precipitates, which are then washed, dried and calcined at 200-800 deg.C. Thus, a powdery starting material having sinterability, uniformity and high bulk density is obtd. at a low cost.

Description

[Detailed description of the invention] [Industrial application field] Perovskite structure (hereinafter referred to as perovskite)
and its solid solutions are piezoelectric and dielectric.

It is widely used as functional ceramics such as semiconductor sensors and optoelectronic materials. Recently, the sophistication of functional ceramics has progressed, and easy sinterability and uniformity meet these demands.

There is a need for the development of a technology that can efficiently produce multiple raw material powders of perovskite and its solid solution with high bulk density and low cost.

Conventionally, dry methods and wet methods are known as methods for producing raw material powders of perovskite and solid solutions thereof.

The dry method involves dry mixing the raw material components.

This is a method of calcining it. However, with this method, it is difficult to obtain raw material powder with a uniform composition, so it is difficult to obtain perovskite and its solid solution with excellent functionality, and the sinterability is also not sufficient.

The wet method is a method in which a mixed solution is prepared by combining all of the constituent components, a precipitate forming liquid such as an alkali is added to this solution, and the coprecipitate is dried and calcined (hereinafter referred to as the coprecipitation method). ).

According to this coprecipitation method, it is easy to obtain powder with excellent uniformity, but
Because of their uniformity, the particles tend to coagulate to form secondary particles during precipitation, drying, or calcination, resulting in poor sinterability.

In addition, in the coprecipitation method, if the precipitate forming ability of each component in the precipitate forming liquid is not the same, for example, the acid component may form 100% precipitate, but all other components may not be able to form precipitate. It may be difficult to achieve the desired composition.

Furthermore, perovskite functional materials very often contain lead and titanium at the same time. When producing such materials industrially, it is desirable to use inexpensive titanium tetrachloride as the titanium raw material. However, when this is used in the coprecipitation method,
Because chlorine ions in titanium tetrachloride react with lead to form a white precipitate.

Difficult to use. In this case, the formation of this white precipitate can be prevented by using titanium oxynitrate [T10(NO3)2] instead of titanium tetrachloride, but titanium oxynitrate is expensive and is not practical for industrial production. .

On the other hand, Japanese Patent Application Publication No. 51-59400 and Japanese Patent Publication No. 54-3
No. 1600 describes a method in which a suspension containing a precipitate obtained by a coprecipitation method is subjected to a hydrothermal reaction at 150 to 300°C. However, this method cannot create a sufficiently homogeneous solution because lead chloride is used as the raw material for lead.
It was difficult to obtain uniform precipitated particles by neutralization, and as a result, the calcined powder showed a wide particle size distribution, and the sintered body could not have a high density.

[Purpose of the invention]

The present invention provides a method that can eliminate the drawbacks of conventional coprecipitation methods, and furthermore, a perovskite and its solid solution that satisfies the four requirements of easy sinterability, uniformity, low cost, and high bulk density, by a wet method. An object of the present invention is to provide a method that can efficiently produce raw material powder.

[Structure of the invention]

As a result of intensive research to achieve the above object, the present inventors found the general formula ABO3 (where A is 1 of the oxygen 12-coordinated metal element).
B represents one or more oxygen hexacoordination metal elements. ) When producing the raw material powder of perovskite and its solid solution represented by
A seed or two or more species are prepared, and an aqueous solution of a compound containing a metal element other than the above is prepared, and these solutions are sequentially added to a precipitate forming solution to form a precipitate. ℃, the obtained precipitate (perovskite precursor) was washed with water, dried, and heated to 200 to 800℃.
Producing the raw material powder by calcination at °C eliminates the drawbacks of the conventional coprecipitation method, and the resulting raw material powder has a uniform particle size.

In addition, the present invention was achieved by discovering that the composition is uniform and that easily sinterable perovskite and its solid solution raw material powder can be manufactured very industrially advantageously.

The present invention relates to a perovskite represented by the general formula ABO3 (where A represents one or more kinds of 12-coordinated metal elements of oxygen, and B represents one or more kinds of 6-coordinated metal elements of oxygen). When producing the raw material powder for the mold structure and its solid solution, one or more aqueous solutions of compounds containing the metal elements of component A and/or component B are prepared, and an aqueous solution of compounds containing metal elements other than the above is further prepared. These solutions are sequentially added to a precipitate forming solution to form a precipitate.

Next, the precipitate slurry is heated at 130 to 600°C, and the obtained precipitate is washed with water, dried, and then calcined at 200 to 800°C. This relates to a manufacturing method.

As the oxygen 12-coordination metal of the A component of the general formula AB○3, 1, for example, + P b + Ba, Ca, S r and L
Examples include rare earth elements such as a. In addition, the oxygen hexacoordination metal element of component B is 9, for example, Ti, Zr, M7, Sc.
・Hf+ Th+ W, Nb+ Ta+ Or
, Mo, Mn, Fe+ Cot Ni.

Examples include Zn, ca, At, Sn, As+Bi, and the like.

A component which is a constituent of perovskite and its solid solution and /=! The component compounds used to prepare an aqueous solution of each compound of component B include, but are not particularly limited to, their hydroxides, carbonates, inorganic salts such as carbonates, sulfates, nitrates, and chlorides, and acetates. , organic acid salts such as oxalate, and oxides.

These are generally used as aqueous solutions. If it is not soluble in water, an acid may be added to make it soluble.

Precipitation forming liquids include ammonia, ammonium carbonate,
Examples include caustic alkali.

In order to generate precipitates of the constituent components, an aqueous solution of each constituent component may be added to the precipitate forming liquid while stirring the precipitate forming liquid, or vice versa.

When adding, it is preferable to stir the liquid sufficiently. When forming a precipitate, for example, after forming a precipitate of one component, washing with water to remove anions, and then dispersing the precipitate in fresh water. Then, an aqueous solution of other components and a precipitate forming liquid may be further added to form a precipitate.

Furthermore, after forming the precipitate of component A and/or component B, by appropriately selecting the type and concentration of the precipitate-forming liquid, a precipitate of a compound containing a metal element other than those mentioned above may be formed.

The slurry containing the precipitate obtained by the above method was heated to 160 ml.
As a method for heating (hydrothermal) treatment at ~300'C, it is common to use an autoclave. Through this treatment, the precipitate becomes perovskite precursor particles with a desired metal atomic ratio, and uniform crystal grains are obtained. If the heating (hydrothermal) treatment temperature is too low, crystallization will not progress sufficiently and it will be difficult to obtain a perovskite precursor with uniform particles that are suitable for sintering; if the heating (hydrothermal) treatment temperature is too high, it will be uneconomical and The particles become larger in size. Therefore, the heat treatment temperature is 160~
This heat treatment yields a perovskite precursor with uniform crystal grains of 0.01 to 0.05 μm suitable for sintering. In addition, in the case of hydrothermal treatment, the pH of the slurry of the precipitate is adjusted to pH 11 with caustic alkali.
It is preferable to carry out the above procedure.

The crystal precipitated particles thus obtained are dried.

When calcined at 200 to 800° C., a compositionally uniform and easily sinterable raw material powder of perovskite and its solid solution with two uniform particle sizes is produced with good reproducibility. Further, a multi-element perovskite with a desired metal element composition can be manufactured.

〔Example〕

EXAMPLES The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Example 1 Lead nitrate 66.2 a y, Okine zirconium nitrate 2
1 t of solution was prepared by dissolving 3.127 in water. While stirring this aqueous solution, 1 t of 6N ammonia water was added to form a precipitate of the above two components, and titanium tetrachloride 18
．． Pb, by adding 400 CC of an aqueous solution containing 99
A homogeneous precipitate of Zr and Ti was produced.

After removing the ammonia content from this precipitate slurry, the pH was adjusted to about 12 with caustic soda, and the slurry was transferred to an autoclave and subjected to hydrothermal treatment at 250° C. for 2 hours.

After thoroughly washing and drying the hydrothermally treated precipitate (pre-perovskite, precursor), it was heated in a Matsufuru furnace at 50″C, 2
Pb (Zr65 Tio, 5) 03 after heat treatment for a time
A powder was obtained.

After taking a portion of this powder and ball milling it.

Observation of the particle shape of the calcined powder using a scanning electron microscope revealed that it contained almost no secondary agglomerated particles.

The average particle size is 0.33 μm and the particle width is 0.12 to 0.4
It was in the range of 2μA.

0.8 g of polyvinyl alcohol (hereinafter abbreviated as PVA) was added to this powder and molded at 1 tonm.
Its density after firing in a lead atmosphere for about 4 hours at C was 7.99.
It was f/CO.

Comparative Example 1 A calcined powder of Pb(ZrO2Tio, 5)03 was prepared in the same manner as in Example 1 except that the precipitate slurry was not hydrothermally treated in an autoclave.

As a result of particle observation of this powder using a scanning electron microscope, the average particle diameter was 0.38 μm and the particle distribution was 0.01 μm.
It was ~0.56 μm.

This powder was added with 0.8% PVA, molded at 1 ton/crA, and fired at 1100'C in a lead atmosphere for about 4 hours, resulting in a density of 7.80? /QC.

Example 2 In Example 1, the hydrothermal treatment temperature of the precipitate slurry was changed to 25
Pt) (Zro, s Tio, 5) 03 calcined powder was obtained in the same manner as in Example 1, except that 0''C was changed to 200°C.

As a result of observing the particles of this powder using a scanning electron microscope, the average particle diameter was 0.34 μm, and the 9-particle distribution was 0.13 to
It was 0.51 μm.

PVA was added to this powder by 0.8%, it was molded at 1 t/i, and it was fired at 1100° C. in a lead atmosphere for about 4 hours, and the density was 7.95 g/CC.

Comparative Example 2 Lead chloride 55.6 f, zirconium oxychloride 32.
Add 22 to 400 Co of water and add 1 while stirring.
．． 9 mol titanium tetrachloride aqueous solution 51 (A: add j,
Make a total solution of 500 CG.

Add 100 QC of 1ON caustic soda aqueous solution to this solution while stirring thoroughly, and add water to make the total volume 700.
I made it into a cc slurry.

The above precipitate slurry was placed in an autoclave and subjected to hydrothermal treatment at 250°C for 4 hours.

The obtained precipitate was washed with water, dried at 70°C for 20 hours, and then heat-treated at 500°C for 2 hours in a Mac furnace to form Pb(Z
rO,5Ti(1,5)03 powder was obtained.

As a result of particle observation of this powder using a scanning electron microscope, the average particle diameter was 0.56 μm, and the particle distribution was 0.0 μm.
It was in a wide range of 5 to 1.2 μm.

Further, 0.8% PVA was added to this powder, molded in 1 ton L, and fired at 1100° C. in a lead atmosphere for about 4 hours. Its density was 7.53 if/CC.

Example 3 Lead nitrate (Pb(NO3)2) 60.28 ? *Lanthanum nitrate (La (NO3)3 ・6H20) 7.7
9 f, zirconium oxynitrate (ZrO(NO3)
2-2H20) An aqueous solution in which 33.98 ft' was dissolved in 1 t of water was dropped into 1 part of stirred 2N ammonia water to form a precipitate. Titanium tetrachloride (T
iq14) 13. Add solution ao to 7 in which Oqt was dissolved.
o ac was added to obtain a dense precipitate of lead, lanthanum, zirconium, and titanium hydroxides. After washing this precipitate slurry, 6N'-caustic soda (NaoH) was added and p
The mixture was adjusted to H=12 and transferred to an autoclave, where it was subjected to hydrothermal treatment at 270° C. for 2 hours.

After thoroughly washing and drying the hydrothermally treated precipitate (belovskite formation), it was heat-treated at 500°C for 22 hours in a Matsunolu furnace to form PbO,9,ILao,o9 (Zr
A powder having a composition of 6.65 rTi(1,3s), q'T'l5O3 was obtained.

After this powder was pulverized using a wet ball mill using ethanol, the particles of the powder were observed using a scanning electron microscope, and a powder having a substantially uniform particle size with an average particle size of 0.11 μm was obtained. As a result of measuring compositional fluctuations using X-ray diffraction, almost no fluctuations were observed.

This powder was molded at 1.5 t/cTA and sintered at 1120° C. for 40 hours in a mixed atmosphere of oxygen gas and lead vapor. The density at that time is 7.83, and the transmittance is 74 coefficient (1 pigeon thickness)
Translucent PLZT of 100% was obtained.

Example 4 Lead nitrate (Pb(NO3)z) 66.2 ay,
Zirconyl nitrate A (ZrO(NO3)2) 6.12
6 S', magnesium nitrate (Mf(NO3)z・6
H20) 1ON solution of 8.5461 dissolved in 300 m/of water - 200 m/! of caustic soda! In addition to.

A precipitate is formed, and titanium tetrachloride (Tict) is added to this solution.
4) 13.85 r and niobium chloride (N bcz, )
18.012 to 100. A solution of J dissolved in water was added to form a precipitate. This precipitate was subjected to a hydrothermal reaction at 250°C for 2 hours. The hydrothermally treated precipitate (composite perovskite formation) was thoroughly washed, dried, and then heat treated in a Matsufuru furnace at 600'C for 2 hours to 50[P cold S'l/3
Nb2/3) 03':l -! 16.5 (pbTi
o3) A powder with a composition of -13,5(PbZrO+) was obtained.

After processing this powder in a wet ball mill using ethanol, it was observed using a scanning electron microscope and found that the average grain size was 0.
．． The particles were uniform in both cases.

This powder was molded at 1.5 t/17A and sintered at 1150°C in a lead atmosphere for 2 hours. Density at that time is 7.9497C
It was C.

〔Effect of the invention〕

According to the method of the present invention, unlike the conventional coprecipitation method in which all components are coprecipitated at the same time, precipitates are generated sequentially and the precipitates are crystallized by hydrothermal treatment, so that each particle is highly dispersed. The powder is obtained in a state where the grain growth is suppressed during drying or calcination, and there are few secondary particles. Raw material powders of perovskite and its solid solution can be efficiently produced.

Furthermore, even if an inexpensive chloride such as titanium tetrachloride is used as a raw material, it is possible to obtain a suitable raw material powder for perovskite and its solid solution by separating it from a solution of a lead-containing compound and producing precipitation in multiple stages. .

Furthermore, by appropriately selecting the components to be precipitated first, the powder characteristics of the produced precipitate can be easily controlled.

Claims (1)

[Claims] The perovskite structure represented by the general formula ABO_3 (where A represents one or more 12-coordinate oxygen metal elements, and B represents one or more 6-coordinate oxygen metal elements) and its When producing solid solution raw material powder,
Making one or more aqueous solutions of compounds containing metal elements of component A and/or component B, further making aqueous solutions of compounds containing metal elements other than those mentioned above, and sequentially converting these solutions into a precipitation forming solution. Easy sinterability characterized by adding the precipitate to form a precipitate, then heating the precipitate slurry at 130 to 600°C, washing the obtained precipitate with water, drying, and then calcining at 200 to 800°C. A method for producing perovskite and its solid solution raw material powder.