JPS63218504A - Production of perovskite type compound - Google Patents

Abstract

PURPOSE:To easily obtain the crystalline powder of the title composite oxide, by allowing the water-soluble salts of plural metals to react with each other in an aq. alkaline soln., mixing the reaction product into an org. solvent having higher b.p. than water, and treating the product at a temp. higher than the b.p. of water. CONSTITUTION:An organometallic compd. forming the oxide, hydroxide, and hydrated oxide or plural water-soluble metal salts by hydrolysis or the oxide, hydroxide, and hydrated oxide are prepared. The compds. are allowed to react with each other in an aq. strongly alkaline soln., the obtained reaction product is mixed into an org. solvent having >=100 deg.C b.p., and the mixture is heated at >=100 deg.C. Or the mixture is further distilled to decrease the water content in the mixture. As a result, the crystalline perovskite type compd. contg. plural metals is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing raw material powder for ceramic materials.

Conventional technology Conventionally, the method for manufacturing composite oxide ceramic raw material powder containing two or more metals involves mixing the contained metal oxides, carbonates, etc. in a ball mill, etc., and calcining the mixture at an appropriate temperature. The method was being used. However, the powder obtained by this method has (1) low sinterability due to its large (and non-uniform) particle size; and (2) large variations in properties due to its non-uniform composition. 3) Because the components are mechanically mixed using a ball mill or the like, there are drawbacks such as the inevitable mixing of impurities.

In order to improve these drawbacks, various powder synthesis methods have been carried out. One of them is a metal alkoxide hydrolysis method. This means that a metal alkoxide represented by M(OR)n (M is an n-valent metal atom, R is an alkyl group) reacts with water to produce a metal oxide or hydroxide and alcohol. For example, BaTiO3, which has a perovskite structure, is synthesized by dissolving Ba alkoxide and Ti alkoxide in a 1:1 molar ratio in ethanol, and then adding water dropwise to the solution to cause hydrolysis ( (Japanese Patent Application Laid-Open No. 57-82119). The powder obtained by this method is already crystallized at a low temperature of 70 to 80°C during powder generation, has a fine particle size, has excellent sinterability, and is free of impurities during mixing with a ball mill etc. There were many advantages, such as:

Oxides containing two or more metals that can be synthesized as crystalline powder by a similar method include SrTiO3, Ba
(Tie-xZrx)O+3゜BaZr0a, (Bat
-XSr
nFe20a.

(Mnl-xZnx)Fe2es, ferrite compounds such as NiFe2O* (Japanese Unexamined Patent Publication No. 56-26726),
Germanic acid salts such as 5rGeO3, PbGeO3, ZnGe04 (Japanese Unexamined Patent Publication No. 1997-19971), PbWO
*, S rAs 20a, etc. are known. However, a major problem with this metal alkoxide hydrolysis method is that the metal alkoxide as a raw material is very expensive.

As an alternative to this, a method has been developed in which salts of two or more metals or their hydrolyzed products are reacted in a strongly alkaline aqueous solution to synthesize a raw material powder with a fine particle size. This method does not require the use of expensive raw materials such as metal alkoxides (the powder produced is crystalline and fine particles, and it is possible to avoid contamination with impurities due to mechanical mixing, making it an excellent method. be.

BaTi03 (Industrial Chemistry Magazine, Vol. 71, No. 1,
JP-A No. 59-39726), Ba (Tit-x
Z rx) 03 (Japanese Unexamined Patent Publication No. 103030/1983)
, (Bad-xSrx)Ties, PbTiOs (Japanese Patent Application Laid-open No. 158820/1982), simple perovskite type compounds or solid solutions thereof can be mentioned.

Problems to be Solved by the Invention In this method, when a hydrolysis product of a metal salt is used as a raw material, the reaction takes time because the solid phase raw material is reacted through a strong alkaline aqueous solution. In order to increase the reaction time, it is necessary to raise the reaction temperature. However, since the solvent is water, the upper limit is 100°C under 1 atm. If you want to carry out the reaction at a higher temperature in a short time with good yield. 100℃ for crystallization, such as pbTies.
Autoclaves have been used when higher reaction temperatures are required. This autoclave itself is expensive, and since it is a high-pressure reaction vessel, it is difficult to handle.

Furthermore, in reactions using water as a solvent, if the components include metals that produce water-soluble oxides, compositional deviations from the blended composition tend to occur (in order to prevent this, the blended composition must be changed in advance). In order to make it insolubilized, it was necessary to add other components (Japanese Patent Application Laid-open No. 31345/1983).

Means for Solving the Problems The present invention provides water-soluble salts of two or more metals, or organometallic compounds that produce oxides, hydroxides, or hydrated oxides upon hydrolysis, or oxides or hydroxides. , hydrated oxide,
The reaction is carried out in a strongly alkaline aqueous solution, and then the reactant is mixed in an organic solvent with a boiling point of 100°C or higher and heated, or further the solvent is partially removed by distillation to determine the water content in the mixture. This is a method for synthesizing a crystalline perovskite type compound containing two or more types of metals, which is characterized in that the reaction temperature is 100° C. or higher.

Effects of the present invention The boiling point of the mixture of water and a high-boiling organic solvent is 10
It takes advantage of the fact that the temperature rises above 0°C, and it makes it possible to synthesize crystalline composite oxide powder at low cost and with good yield, without using special reaction equipment such as an autoclave. Although the boiling point organic solvent itself is much more expensive than water, as can be easily inferred from the synthesis method, it can be recovered 100% after the reaction is completed, and the increase in production cost due to this is small.

Examples Example 1 Titanium hydroxide synthesized by adding an alkali to an aqueous solution of titanium chloride and commercially available barium hydroxide were each weighed in an amount of 0.1 mol so that the molar ratio was 1:1, and this was added to 50 mol of water.
This flask was set in an oil bath, and the mixture was heated under reflux at 100°C for 1 hour in a N2 stream. 10,100 O of n-pentanol was added to this, and up to 40 ml of 50 ml of water was removed by distillation. As a result, the boiling point was 115°C. The reaction was continued in this state for an additional hour. For comparison, boiling point (
Samples were also prepared that were reacted at a temperature of approximately 100°C for the same period of time.

The resulting precipitate was separated using a centrifuge and dried at 120°C to form a powder. The powder thus synthesized was subjected to X-ray diffraction measurement, and the amount of crystalline herovskite phase (BaTiO3) produced was determined from the area of the diffraction peak.
In the former reaction using a water-n-pentanol system, the production rate was 96%, whereas in the case of reacting only with water, the production rate was 78%.

Example 2 Lead acetate and Ti isopropoxide were each hydrolyzed,
Fine-particle, amorphous hydrous lead oxide and titanium hydroxide were synthesized. These are each 0.105m so that PbTi03.05.

1 and 0.1 mol were weighed out, and 100 ml of an aqueous NaOH solution whose pH was adjusted to 13.5 was added thereto. After heating the mixture to reflux at 100°C for 5 hours in a N2 stream,
10,100 O of n-hexanol was added to this, and up to 90 ml of 100 ml of water was removed by distillation. As a result, the boiling point was 135°C. The reaction was continued in this state for an additional 5 hours. For comparison, the boiling point (
Samples were also prepared that were reacted at a temperature of approximately 100°C for the same period of time.

The resulting precipitate was filtered and washed with pure water (after washing,
It was dried at ℃ to form a powder. When the powder thus synthesized was subjected to X-ray diffraction measurement, it was confirmed that in the former water-n-hexanol system, a broad but crystalline herovskite phase (PbTi03) was formed. On the other hand, when the reaction was carried out with only water, the reaction was completely amorphous. ◇Example 3 Similar to Example 1, titanium hydroxide synthesized by adding an alkali to an aqueous solution of titanium chloride and commercially available barium hydroxide were combined in mol. Weigh out 0.1 mol of each so that the ratio is 1:1, mix it with 50 ml of water, put it in a flask, set the flask in an oil bath, and add 1 mol in a N2 stream.
The mixture was heated under reflux at 00°C for 1 hour. Add xylene 1000 to this
4 out of 50 ml of water by distillation.
I pulled out up to 0m1. As a result, the boiling point was 105°C.

After reacting in this state for another 1 hour, distillation was performed again to drain all the water. As a result, the boiling point was 138°C. For comparison, a sample was also prepared in which water was reacted at the boiling point (approximately 100°C) for the same period of time.

The resulting precipitate was separated using a centrifuge and dried at 120°C to form a powder. When we analyzed the composition of the powder synthesized in this way, we found that in the former water-xylene system, Ba
TiO3,OO, but in the latter water-only method,
BaTiO3°92.

Effects of the Invention The present invention provides water-soluble salts of two or more metals, or organometallic compounds that produce oxides, hydroxides, or hydrated oxides upon hydrolysis, or oxides, hydroxides, or hydrated oxides. of,
The reaction is carried out in a strongly alkaline aqueous solution, and then the reactant is mixed in an organic solvent with a boiling point of 100°C or higher and heated, or further the solvent is partially removed by distillation to determine the water content in the mixture. This is a method for synthesizing a crystalline composite oxide containing two or more types of metals, which is characterized in that the reaction temperature is 100° C. or higher.

According to the present invention, a complex oxide containing two or more metals can be prepared without using a special pressure vessel such as an autoclave.
It is possible to easily and inexpensively produce fine-particle, highly pure crystalline powder.

Claims (2)

[Claims] (1) Water-soluble salts of two or more metals, or organometallic compounds that produce oxides, hydroxides, or hydrated oxides by hydrolysis, or oxides, hydroxides, or hydrated oxides, in a strongly alkaline solution. React in an aqueous solution, then mix this reactant in an organic solvent with a boiling point of 100°C or higher and heat it, or further remove some of the solvent by distillation to reduce the water content in the mixture. 1. A method for producing a perovskite compound, which comprises producing a crystalline perovskite compound containing two or more metals at a reaction temperature of 100° C. or higher. (2) At least one oxide of two or more metals is water-soluble, and all water in the reaction system is evaporated by distillation of a mixture of raw materials, water, and an organic solvent. , a method for producing a perovskite compound according to claim 1.