JPH06345520A - Production of multiple oxide - Google Patents

Abstract

PURPOSE:To provide a more convenient process producing composite oxides having a perovskite or composite perovskite structures, in which a compound shown by the structural formulas such as ABO3, A(B<1>1/3B<2>2/3)O3, A(B<3>2/3B<4>1/3)O3 and A(B<5>1/2B<6>1/2) or the solid soln. thereof are contained and being difficult to be sintered. CONSTITUTION:The peroxides of alkali or alkaline-earth metals are used as one or >=1 kind of the constituent, and a uniform multiple oxide is synthesized by heat treatment at a low temp. Since a multiple oxide powder finer than the conventional solid-phase process and having a higher activity is obtained, the perovskite-structure compd. is produced at a lower temp. than in the well- known conventional solid-phase reaction process. Further, as the heat history of the obtained powder is short as compared with the process by the prior art, the powder has a higher surface sctivity, and the powder is sintered at a low temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a perovskite complex oxide used as an electronic material such as a piezoelectric element and a dielectric.

[0002]

2. Description of the Related Art Conventionally, in the production of composite oxides, the powder of each component or its precursor is mixed, and the physically homogeneously mixed raw materials are baked to form a solid-phase reaction. A composite oxide having the component composition of

However, in the preparation by such a solid phase reaction, the progress of the reaction is slow, so that the method of mixing powders of the respective components and firing the mixture requires a high temperature for the reaction of the respective components. However, the obtained powder easily causes grain growth and is difficult to be made fine, and it is difficult to completely react each component with each other in the solid phase reaction. The powder thus obtained usually has low activity and requires firing at a high temperature and addition of a sintering aid in order to obtain a sintered body. Therefore, it is difficult to control the desired chemical composition, and the properties of the obtained product are inferior.

Further, in order to obtain a finer powder in which the components are uniformly dispersed, a wet coprecipitation method or a production method using a metal alkoxide as a starting material has been tried.

For example, "Journal American Ceramic Society (J. Am. Ceram. So
c. ), Issued 1966, 291, 49 ",
In "1969, 523, 52", and also in "1970, 53, 91," BaTiO
_{For the} production of fine particles without deviation of the composition of ₃ and SrTiO ₃ .
It has been reported that production using a metal alkoxide is possible.

However, in the wet coprecipitation method, it is difficult to set the conditions for precipitating multiple components at the same time.
Alkaline earth metals such as Zn and transition metals such as Zn are simply pH
It is difficult to precipitate only by preparing. As a result, the composition of the obtained composite oxide precursor deviates from the intended composition, and the characteristics of the final product such as ceramics are deteriorated.

Further, in the metal alkoxide method, the metal alkoxide as a starting material is expensive except for some elements such as Si and is not practical to use in large quantities. Also, many of the metal alkoxides have low solubility in organic solvents, and it is necessary to study the use of large amounts of solvents and combinations of various organic solvents in order to prepare a uniform solution for hydrolysis, which is necessary for production. The volume is quite large. As a problem in operation, since metal alkoxide is unstable to water, it is necessary to handle it in an atmosphere containing no water. In particular, for alkali metal and alkaline earth metal alkoxides, the hydrolysis product obtained when carbon dioxide gas coexists forms a carbonate, so it is necessary to decarboxylate the water to be added. When it is applied to the production of a type of complex oxide, there is a problem that its adjusting operation is difficult.

Further, as a method for synthesizing a composite perovskite powder, Japanese Patent Laid-Open No. 58-199716 discloses a perovskite type compound of a metal oxide, a piezoelectric ceramic material and a dielectric ceramic material as A alone, and A as B.
a, Sr, Ca, Pb as an element, B as a rare earth element, actinide, Fe, Co, Mn, Ni, R
An element selected from h, In, Ga, V, Cr, Al, Zn, and Mg, and B ² as Nb, Sb, or Ta, have an A (B ¹ 1 / 3B ² 2/3) O ₃ structure. It is disclosed to synthesize a composite perovskite powder having three or more components at a low temperature.

Further, in Japanese Patent Laid-Open No. 62-87456, it is possible to control the oxygen partial pressure in a reducing atmosphere by adding a peroxide of an alkaline earth metal to a pre-synthesized perovskite powder. It is disclosed that the base metal electrode can be fired at the same time.

Further, in Japanese Patent Application Laid-Open No. 63-297262, when SE is a rare earth metal and EA is an alkaline earth metal, an oxide superconductor of SE-EA-Cu-O is chemically and physically prepared. In the production in a closed high-pressure vessel, by adding a thermally decomposable alkaline earth metal peroxide for adjusting the oxygen partial pressure, the composition corresponding to the composition of the specific coexisting phase of the superconductor. It is disclosed that the desired superconductor phase is thermodynamically stabilized by covering it with a protective layer having.

[0011] Furthermore, the Institute of Electronics and Communication Engineers Materials Research Materials, C
PM86-31, p41 (1986) contains Ba (Mg
It has been reported that a rapid heating method in which a compact is rapidly charged into a furnace is effective for producing a 1 / 3Nb2 / 3) O ₃ type sintered body.

[0012] However, the temperature rising method is one of the effective methods for increasing the density of the difficult-to-sinter material, but it requires a special baking apparatus and is therefore expensive. It is not suitable for manufacturing shaped products.

However, the above-mentioned conventional method for producing perovskite powder has a problem that it requires an expensive facility as an industrial production method, or various problems to be solved in terms of producing a large-sized product. .

[0014]

An object of the present invention is to provide a simpler method for producing a perovskite type composite oxide.

[0015]

The production of the perovskite type complex oxide according to the present invention is characterized by using one or more of the constituent components as an alkali or alkaline earth metal peroxide.

The present invention is generally effective in the production of a compound having a perovskite or complex perovskite structure which is difficult to sinter. For example, the structural formula ABO ₃ , A
(B ¹ l / 3B ² 2/3) O ₃ , A (B ³ 2 / 3B ⁴ 1
/ 3) O ₃ and compounds represented by A (B ⁵ 1 / 2B ⁶ 1/2) O ₃ and solid solutions thereof. A is Ba, Sr,
There are Ca, Mg, Li and the like. B includes Ti, Zr, Sn and the like. B ¹ is Mg, Ca, Sr, Ba, Ni, Zn, C
There are o etc. B ² includes Ta, Nb, V, Sb and the like. B
³ and B ⁵ have Fe and the like. B ⁴ has W etc. B ⁶ is N
b etc. These elements exclude alkaline earth metals,
Used as an oxide.

The alkali or alkaline earth metal which is a constituent element of the A site is used in the form of peroxide. For example,
There are peroxides of alkali metals such as lithium peroxide, sodium peroxide and potassium peroxide, and alkaline earth metal peroxides such as magnesium peroxide, calcium peroxide, strontium peroxide and barium peroxide. A perovskite compound containing these elements at the B site can also be used.

By heating the mixed powder containing one or more peroxides, the desired composite oxide can be obtained. The heat treatment temperature is set individually because the suitable temperature varies depending on the individual compound. The obtained powder is mixed with an organic binder or the like and then molded into a desired shape by a known method. For example, molded articles of various shapes can be obtained by the uniaxial pressing method, CIP method, casting method, injection method, doctor blade method or the like. The molded body is fired in an oxidizing atmosphere or a non-oxidizing atmosphere depending on the purpose and composition. The firing temperature is individually determined by the composition.

[0019]

The action of the alkali metal or alkaline earth metal peroxide used in the present invention has not been clearly clarified, but it is considered to have the following action.

Alkali metal or alkaline earth metal peroxides are melted and decomposed at a low temperature of 1000 ° C. or less to form fine oxides. As a result, the resulting melt or fine particles are mixed with other components. Therefore, it is considered that the compound oxide can be uniformly permeated and dispersed, and a uniform composite oxide is generated at a lower temperature. Since a complex oxide powder finer and more active than the ordinary solid-phase method can be obtained, the perovskite compound can be produced at a lower temperature than the already known ordinary solid-phase reaction method using a carbonate. Further, the obtained powder has less heat history and higher surface activity as compared with the conventional method, and thus low temperature sintering becomes possible.

[0021]

Examples As examples of the present invention, starting materials, formation temperatures, specific surface areas of the obtained powders, and target complex oxides are shown in Table 1.
Summarized in.

As the starting materials shown in Table 1,
As an alkali or alkaline earth metal peroxide, B ₄
O ₂ , SiO ₂ and LiO ₂ were used and weighed so that the composition ratio of the target composite oxide was obtained. The mixed oxide was wet-mixed in methanol, dried, and calcined at a temperature of 300 to 1400 ° C. in steps of 50 ° C. in the atmosphere for 2 hours. The crystal phase of the obtained powder was measured by the powder X-ray diffraction method. As a result, it was found that the target perovskite compound was obtained.

[0023]

[Table 1] As a comparative example, a complex oxide powder was similarly prepared using the carbonate shown in Table 1 as a starting material.

The perovskite complex oxides shown in Examples 1 to 6 are prepared by using the A-site metal peroxide.
Compared to the case of Comparative Example 1-3 using ordinary carbonate, the number 1
Low temperature synthesis of 00 ° C is possible. As a product,
Specific surface area of 2.5 m ² / g or more (specific surface area diameter 0.5 μm
The following fine powder was obtained.

As shown in Examples 7 and 8, Ba (Mg1 / 3Ta2 / 3) O ₃ having a composite perovskite structure.
As the powder, a single-phase powder having a specific surface area of 0.5 μm or less could be synthesized at a low temperature of 150 ° C. as compared with Comparative Examples 4 and 5 of the conventional method. In particular, the columbite method (B site elements MgO and T
a ₂ O ₅ is reacted in advance to synthesize MgTa ₂ O ₆ .
In Example 8 in which this is used together with the method of reacting it with Ba which is an A site element, Ba (Mg1 / 3T) at 1050 ° C.
Since a single-phase powder of a2 / 3) O ₃ can be obtained and the target product can be obtained by calcination at a lower temperature, it can be seen that it is more effective. Comparative example 5 even when the columbite method was used together
It can be seen that the conventional method of (1) requires a high temperature of 1250 ° C. to obtain a single-phase powder, and the specific surface area is as small as 0.6 m ² / g.

[0026]

The uniform powder can be synthesized at a lower temperature than the conventional method.

As a result, since the obtained powder is obtained at a low temperature, grain growth has not progressed so much, so that it is easy to pulverize and it is possible to minimize contamination of impurities during pulverization.

Further, it is possible to obtain a powder of perovskite type complex oxide having a high surface activity and excellent sinterability as compared with the conventional method at a low temperature.

Therefore, it is not necessary to add a second component such as a sintering aid in the sintering machine, and a sintered body having a composition close to the stoichiometric ratio can be easily manufactured.

Claims (1)

[Claims] 1. A method for producing a perovskite type complex oxide, which comprises subjecting one or more of the composition components as a peroxide of an alkali or alkaline earth metal to a heat treatment, and carrying out heat treatment.