JPS63285151A - Production of perovskite ceramic - Google Patents

Abstract

PURPOSE:To obtain high-density functional ceramic of perovskite type having readily sintering properties, by preparing raw material powder of modified zirconium oxide by coprecipitation method and rapidly cooling a sintered material in preparation of ceramic raw material powder. CONSTITUTION:Zirconium-containing perovskite ceramic shown by general formula ABO3 (A is metallic element of 12 oxygen; B is metallic element of 6 oxygen coordination) is formed by the following three processes. [first process] A mixed solution of partial amount of components constituting the perovskite compound except zirconium and a zirconium solution is formed, the mixed solution is blended with a coprecipitation forming solution, a coprecipitated material is formed, dried, fired at 700-1,300 deg.C and rapidly cooled. [second process] The fired material of the first process is mixed with a compound as the residual constituent component of perovskite compound in a mixed state, dried, the dried material is fired at 700-1,300 deg.C and the fired material is rapidly cooled. [third process] The fired powder of the second process is molded and sintered at 700-1,700 deg.C. The rapid cooling of the first and the second process is carried out preferably at >=50 deg.C/min rate of temperature drop.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing perovskite ceramics.

Perovskite ceramics are used in a wide range of fields as functional ceramics such as piezoelectric materials, optoelectronic materials, dielectrics, semiconductors, and sensors.

(Prior art and its problems) Many important perovskite functional ceramics contain zirconium.

Conventionally, a dry method has been widely used as a method for producing perovskite raw material powder. However, when perovskite raw material powder is prepared by a dry method using zirconium oxide powder as a starting material, the particle size of commercially available zirconium oxide powder is 1 μm or more, so the obtained perovskite raw material powder also has a particle size of 1 μm or more. It becomes 2 μm or more. If a perovskite raw material powder with a particle size of this size is used, the sinterability is not good, and it is difficult to obtain functional ceramics with high density and advanced functionality.

(Object of the Invention) The present invention was made in order to eliminate the drawbacks in the dry synthesis of perovskite ceramics, and its purpose is to produce submicron-grade modified zirconium oxide raw material powder with good dispersibility by a coprecipitation method. The object of the present invention is to provide a method for producing easily sinterable and high-density perovskite-based functional ceramics by a simple dry method using the powder.

(Technical means for solving the problem) As a result of intensive research to achieve the above object, the present inventors found that the general formula A, DO3 (where A is an oxygen-12-coordinated group element, and B is an oxygen When a zirconium precipitate is formed by mixing a zirconium alone solution and a precipitate forming solution in the dry process of manufacturing perovskite ceramics containing zirconium (B position), which represents a hexacoordinated metal element. The precipitate obtained will be very agglomerated, but by mixing the zirconium solution and a partial amount of the components other than zirconium constituting the perovskite compound, and mixing this mixed solution and the precipitate forming solution, the precipitate can be made into a precipitate. When RI is formed, a coprecipitate with extremely low RI collection is obtained. After calcining this coprecipitate, the calcined product is rapidly cooled to produce submicron-level powder with good dispersibility (altered oxidation Furthermore, using this modified zirconium oxide powder as a raw material, wet-mixing the remaining components of the perovskite compound, calcining the mixture, and rapidly cooling the fired product. For example, a raw material powder with excellent submicron-level powder properties can be easily obtained, and by molding and sintering this raw material powder, extremely high-density perovskite ceramics can be easily obtained even without the use of sintering aids. The present invention was based on this discovery.

That is, the present invention involves forming a mixed solution of a partial amount of components other than zirconium constituting a perovskite compound and a zirconium solution, mixing this mixed solution with a precipitate forming solution to form a coprecipitate, and washing. , 700-130 after drying
After calcining at 0°C, the calcined product is rapidly cooled in the first step. The calcined product from the first step and the remaining components of the Belkovskite compound are wet-mixed, and then dried to obtain a dried product. A second step of rapidly cooling the fired product after calcination at 500 to 1,300°C, and a third step of molding the calcined powder of the second step and sintering at 700 to 1,700°C. This invention relates to a method for producing perovskite ceramics.

As the A component (oxygen 12-coordinated metal element) of the perovskite compound represented by the general formula ABO3, for example, Pb
, Ba, Ca, Sr, and La. In addition to zirconium, the B component (oxygen hexacoordination metal element) includes, for example, Ti, Mg, Sc, Hf, '
T'h; W, Nb, Ta, Cr', Mo, Mn.

Examples include Fe, Co, Ni, Cd, l2, Sn, As, Bi, and the like. The present invention also includes those in which the molar ratio of component A and component B is shifted to a value higher or lower than 1.0.

Each step of the present invention will be explained below.

First step: Examples of compounds for preparing the zirconium solution include zirconium oxychloride, zirconium oxynitrate, zirconium chloride, zirconium nitrate, and metal zirconium, and water and alcohol are usually used as the solvent.

Compounds of perovskite components that dissolve in zirconium solution include inorganic salts such as hydroxides, carbonates, oxysalts, sulfates, nitrates, and chlorides, and organic acid salts such as acetates and oxalates. Appropriately selected from. These are generally used as an aqueous solution, but if they are not soluble in water, they can be dissolved by adding an acid.For insoluble raw materials, they can be used as a suspension solution, or an alcohol solution can be used instead of an aqueous solution. may be used.

In the present invention, "partial amount of components other than zirconium"
(1) A partial amount of one component other than zirconium, or a partial amount of two or more components, each of component E, and (2) a total amount of one component other than zirconium, or two or more components. For example, if a perovskite compound is composed of zirconium and two components X and Y other than zirconium, the partial amount of the components other than zirconium is: ■X ■ Partial amount of Y ■ Partial amount of X and Y partial amount ■ Partial amount of X and total amount of Y ■ Partial amount of Y and total amount of X ■ Total amount of X ■ Total amount of Y. .

Examples of reagents for preparing the precipitate-forming solution include organic reagents such as ammonia, ammonium carbonate, caustic alkali, oxalic acid, ammonium oxalate, amines, and oxine.

The obtained coprecipitate was washed and dried, and the dry matter was
After calcining at a temperature of 300°C, the fired product is rapidly cooled.

If the calcination temperature is lower than 700℃, agglomeration will occur significantly, 13
When the temperature exceeds 00°C, the particles tend to become coarse. Furthermore, if rapid cooling is not performed, sintering between particles will be large and the particle size distribution will be poor.

Further, in the perovskite-based functional ceramics, am additives such as boron oxide, bismuth oxide, etc. can be added to improve the sinterability and properties. These auxiliaries can be appropriately added in the first and second steps.

Second step: - Add the remaining components other than zirconium to the calcined powder obtained in the first step and wet-mix. As a solvent, -
Water and ethanol are used for a.

The constituent compounds to be added include their carbonates,
Oxides etc. are used. In this case, by using submicron-grade compound powders, the obtained perovskite powder will also be of submicron-grade powder, resulting in excellent powder properties. However, even if lead oxide powder with a coarse particle size is used, it has almost no effect on the properties of the obtained Perot and Buskaite powders.

Next, the obtained mixture is dried, the dried product is calcined, and then the fired product is rapidly cooled. The calcination temperature is determined depending on whether PB is included, Ba or SR is included, or Nb or Ta is included.
It varies significantly in the range of 700-1300°C. In short, the temperature needs to be higher than the minimum temperature at which the solid phase reaction is almost or completely completed, and within the maximum temperature range at which significant particle growth does not occur.

Furthermore, if rapid cooling is not performed, sintering between particles will be large and the particle size distribution will be poor.

Third step: The calcined powder obtained in the second step is molded and sintered.

The sintering temperature generally ranges from 700 to 1700°C. If the temperature is lower than 700°C, sintering will be insufficient;
If the temperature exceeds 0°C, the sperm become coarse or the constituent components evaporate.

(Example) The present invention will be described in detail below using Examples and Comparative Examples.

Example 1 Aqueous solution of titanium tetrachloride (Ti Cj4) (0,9641
mol/1) 2178 mN and an aqueous solution of zirconium oxynitrate (0,854 mol/41) 226.46 m1
mixed with. This mixed aqueous solution was gradually added to 1j of stirring 6N-ammonia water to form Ti4+ and Zr4+.
A hydroxide coprecipitate of was obtained.

After washing and drying this, the dried material is sized and calcined in a rotary kiln at 1000°C for 30 minutes in an air atmosphere, and then rapidly cooled to room temperature at a cooling rate of 200°C/min to form modified zirconium oxide powder. It was created.

The average particle size of this powder is 0.30μ! n, and had a well-aligned, nearly spherical shape.

6.8293 g of the powder and T with an average particle size of 0.15 μm
i Wet-mix 3.3267 g of O2 rutile fine powder and 2232 g of PBO powder with an average particle size of 13 μm using ethanol in a ball mill for a day and night, then dry it, size the dried product, and heat it in a rotary kiln at 750°C for 1 hour. After baking, it was rapidly cooled to room temperature at a cooling rate of 250° C./min to obtain Pb (Zr, 5Tio, 5)03 powder. The average particle diameter was 0.30 μm, and the shape was well-aligned and nearly spherical. A tablet formed from the powder by It/J was sintered at 1200° C. for 1 hour in an atmosphere containing lead vapor and oxygen gas.

The density of the obtained product reaches 7.95 g/aJ, which is very close to the theoretical density.

Comparative Example 1 A dried hydroxide coprecipitate of Ti'+ and Zr4+ prepared in the same manner as in Example 1 was placed in a crucible and calcined at 1000°C for 30 minutes in an air atmosphere using a Matsufuru furnace. ,
Create a modified zirconium oxide powder by leaving it to cool to room temperature at a cooling rate of 150°C/hour.

Although the average particle size of this powder was 0.30 μm, the shape of the particles was slightly poor, and sintering between particles was observed.

6.8293 g of the powder and Ti with an average particle size of 0.15 μm
O2 rutile fine powder 3.3267g and average particle size 1
After wet-mixing 2232 g of 3 μm Pb0J9 powder with ethanol in a ball mill for a day and night, drying, putting the dried product into a crucible and calcining it at 750°C for 1 hour using a Matsufuru furnace, the cooling rate was 50°C. / hour to room temperature to obtain p b (z ro, 5Tio, s > os powder. The average particle size of this powder was 0.3 μm, but the particle size distribution was poor. molded with it/aJ,
Sintering was carried out in the same manner as in Example 1.

The density of the obtained ceramics is 7.90g,,'! Met.

Example 2 Modified zirconium powder 3 produced in the same manner as Example 1
．． 41. ．． 57 g, 26616 g of pbO powder with an average particle size of 13 μm, 22.32 g of TiO2 fine powder with an average particle size of 013 μm, Nb2 with an average particle size of 0.23 ttm.
M (IQ powder 0, 5038 g) obtained by firing 3.3226 g of O5 fine powder and magnesium hydroxide at 750°C
After wet-mixing using ethanol in a ball mill for a day and night, drying, sizing the dried product and calcining it in a rotary kiln at 750°C for 1 hour, cooling rate of 250°C /
0.375Pb (Mg1,3Nb2/3) 03-0.
375Pb TiO3o, 25PbZrO
A composition powder of No. 3 was obtained. The average particle diameter was 0.34 μm, the particle size distribution was good, and the shape was close to spherical. The powder is
/- molded tablets were sintered at 1200° C. for 1 hour in an atmosphere containing lead vapor and oxygen gas.

The density of the obtained ceramic was 7.97 g/J, which was extremely close to the theoretical density.

Comparative Example 2 A mixture of the modified zirconium powder obtained in the same manner as in Example 2 and the remaining components was placed in a crucible and calcined at 750°C for 1 hour using a Matsufuru furnace, followed by a cooling rate of 150°C/
0.375 Pb (Ma1/3
Nb2/3) 03-0.375 PbTi 03-
A powder composition of 0.25Pb Zr O3 was obtained.

The powder was molded at it/cd and sintered in the same manner as in Example 2. The density of the obtained ceramics is 7.90g/
-It was.

(Effects of the Invention) According to the method of the present invention, the zirconium oxide powder (modified zirconium oxide powder) containing a part of the constituent components of the perovskite compound obtained in the first step is submicron particles with extremely few secondary particles, By using this, it is possible to easily obtain a submicron-level perovskite raw material powder by a dry process, and furthermore, it is possible to obtain an excellent effect in that a ceramic with a high density extremely close to the theoretical density can be obtained using this as a raw material. You can also obtain the following effects.

1) The modified zirconium oxide powder obtained by rapidly cooling the calcined product after calcining has a good iP shape and is sufficiently dispersed. Can be supplied as a powder.

2) After calcining the mixture of the calcined modified zirconium oxide powder and the remaining perovskite compound constituent compounds, the perovskite powder obtained by rapidly cooling the calcined product can also be obtained in a monodisperse state, and therefore Even without the pulverization step, it has sufficient sinterability and high bulk density.

3) Perovskite-based functional ceramics, which require extremely high density, can be produced by simple solid-phase sintering, omitting operations such as hot pressing and 1-11P (hot gas pressure sintering), and by using sintering aids. High densities that are extremely close to the theoretical density can be obtained without necessarily using .

4) By mass-producing modified zirconium oxide powder with excellent powder properties, it is possible to supply berovskite+ raw material powder and high-performance herovskite-based functional ceramics containing countless silconium oxides at extremely low cost.

Claims (2)

[Claims] (1) Form a mixed solution of a partial amount of components other than zirconium constituting the perovskite compound and a zirconium solution, mix this mixed solution and a precipitate forming solution to form a coprecipitate, and after washing and drying. After calcining at 700 to 1,300°C, the calcined product is rapidly cooled in the first step. The calcined product from the first step and the remaining perovskite compound components are wet-mixed, and then dried.
A second step of rapidly cooling the fired product after calcination at 00 to 1,300°C, and a third step of molding the calcined powder of the second step and sintering at 700 to 1,700°C. Method of manufacturing perovskite ceramics. (2) The method for producing perovskite ceramics according to claim 1, wherein the rapid cooling in the first step and the second step has a temperature decreasing rate of 50° C./min or more.