JPS62148322A - Production of raw material powder of perovskite and its solid solution - Google Patents

Abstract

PURPOSE:To obtain the titled low-cost raw material powder which has easily sinterable properties, uniformity and high bulk density by removing at least one component of two kinds of the specified oxygen coordination metallic elements and forming a suspension thereof and thereafter adding the removed component, drying and calcinating the precipitate. CONSTITUTION:A raw material powder of perovskite shown in ABO3 and its solid solution is produced by the following treatment. In other words, a precipitate is firstly formed by precipitate forming liquid in an aq. soln. or an alcoholic soln. of the residual component compd. wherein at least one component of the component A and the component B is removed. Then after mixing the above-mentioned removed component compd. to a suspension thereof, the aimed raw material powder is obtained by drying and calcinating the obtained precipitate at 120-1,200 deg.C. In the formula, A shows oxygen 12 coordination metallic element and B shows oxygen 6 coordination metallic element and the sum of the number of the component A and the component B is >=3 kinds.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing easily sinterable perovskite and its solid solution raw material powder by a wet method, and in particular to dielectrics, piezoelectrics, optoelectronic materials, semiconductors, sensors, etc. The present invention relates to a method for producing perovskite and its solid solution raw material powder that can be used as functional ceramics.

<Prior Art> Conventionally, dry methods and wet methods have been known as methods for producing raw material powders of perovskites and solid solutions thereof (hereinafter both will be referred to as perovskite solid solutions for convenience). The dry method is a method in which all the compounds of the constituent raw materials are mixed in a dry method and then calcined.

On the other hand, the wet method is a method in which a mixed solution of all the compounds of the constituent raw materials is prepared, this is added to the precipitate forming solution to cause coprecipitation, and this coprecipitate is dried and calcined (hereinafter referred to as the coprecipitation method). be.

<Problems to be Solved by the Invention> As mentioned above, the dry method and coprecipitation method are known as methods for producing perovskite solid solution raw material powder, but the former makes it difficult to obtain raw material powder with a uniform composition, and also has poor sinterability. However, there was a drawback that perovskite solid solutions with excellent functionality could not be obtained because the perovskite solid solution was insufficient.

In addition, although the latter method can provide raw material powder with excellent uniformity, it has the disadvantage that the particles coagulate together to form secondary particles, making it difficult to easily sinter. Furthermore, since the concentration of the precipitate forming liquid is constant in the coprecipitation method, there is a drawback that it is difficult to obtain a raw material powder with a desired composition due to differences in the precipitate forming ability of each component.

The present invention was made in view of the current situation,
The object of the present invention is to provide a method for producing a raw material powder for a perovskite solid solution that satisfies all four requirements of ease of sintering, uniformity, high bulk density, and low cost and eliminates the drawbacks of the prior art.

In other words, the present invention has the general formula ABO3 (where A is one or more kinds of oxygen 12-coordinated metal elements, and B is one or two kinds of oxygen 6-coordinated metal elements). The above is expressed, and the sum of the numbers of A components and B components is 3 or more types.

) In the method for producing a raw material powder of perovskite and a solid solution thereof, an aqueous solution or an alcohol solution of the remaining component compounds after removing at least one of the components A and B is used to form a precipitate using a precipitate-forming liquid, and then An easily sinterable perovskite characterized by mixing the above-mentioned removed component (hereinafter referred to as component The present invention relates to a method for producing solid solution raw material powder.

In the present invention, the oxygen 12-coordinated metal element which is the component A in the general formula includes, for example, Pb% Ba, Ca,
Examples include rare earth elements such as Sr and La.

Further, as the oxygen hexacoordination metal element which is the B component, for example, T+, ZrXMg, SC%llfXW% Nb,
, Tas Cr.

Mo, Mn, Fe, Co, Ni, Zr+, Cd, 8! ,
Examples include 5n1AS% B1.

Compounds for preparing an aqueous or alcoholic solution of components A and B, which are constituent components of the perovskite solid solution, include oxides, hydroxides, carbonates, nitrates, acetates, Examples include, but are not limited to, formates, oxalates, metals, and the like.

In addition, the compound of component It is desirable to select a material that causes precipitation or a material that causes precipitation.

The compound of component X is preferably an oxide in many cases, but it may also be the above-mentioned salts, and if there are two or more types of component X, it may be a coprecipitate of these and a calcined product thereof. . In order to uniformly mix the compound of component X with the precipitate of the remaining component compounds, it is desirable to use a compound having an average particle size of 1 μm or less.

In the present invention, examples of the precipitation forming liquid include aqueous or alcoholic solutions of ammonia, ammonium carbonate, caustic alkali, oxalic acid, ammonium oxalate, or amines.

Next, a method for producing the raw material powder of the perovskite solid solution of the present invention will be explained.

First, an aqueous solution or alcohol solution of the remaining A component and B component compound excluding component X is added to the precipitate forming solution while stirring, or vice versa, the precipitate forming solution is added to the above solution to form a precipitate. . Incidentally, when forming a precipitate, an aqueous solution or an alcoholic solution of all component compounds except component X may be added to the precipitate forming solution at the same time, but it goes without saying that each solution may be added sequentially depending on the case.

Furthermore, in addition to components A and B, when adding trace components to control the sinterability and other properties of perovskite,
It may be added when preparing each solution of component A and component B.

Next, the obtained precipitate is stirred to suspend it, and then the powder of the X component compound is added and sufficiently dispersed by means such as ultrasonic waves.

After filtering and washing the mixed precipitate thus obtained,
By drying and calcining at 1200° C., a uniform and easily sinterable perovskite solid solution raw material powder is obtained.

In the present invention, the raw material powder of perovskite solid solution is produced as described above, and the selection of the A component and the B component is as follows:
It can be done as appropriate depending on the purpose. For example, when used as a multilayer ceramic capacitor dielectric, niobium, tantalum, or tungsten may be selected as the X component, and lead (component A), iron, or zinc (component B) may be selected as the remaining components.

By the way, barium titanate has been mainly used as the dielectric material of the multilayer ceramic capacitor, but this barium titanate has a sintering temperature of 1300 to 14
00℃, it was necessary to use expensive platinum, palladium, etc. for internal electrodes, but the raw material powder of perovskite solid solution using the above components obtained by the method of the present invention can be sintered at a low temperature of 1200℃ or less. Because it has , it can be replaced with an inexpensive material such as silver as the internal electrode.

<Effects of the Invention> According to the method of the present invention, the formation of secondary particles is small in both the coprecipitation process and the calcination process of the mixture of the coprecipitate and the X component compound, resulting in a uniform and high Easily sinterable fine particles with bulk density are obtained. Compounds that have different precipitate-forming ability from other constituent compounds, or compounds that are difficult to dissolve in water or alcohol, are treated as X-component compounds and are simply mixed and calcined with the rest of the co-precipitated constituents to achieve the desired perovskite composition. It can be made completely, and furthermore, since the selection range of the X component compound is widened, it has the characteristics that, for example, inexpensive raw materials can be selectively used.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 33.12 g of lead nitrate (A component compound) of reagent special grade (Pb(No:+)z 99.5% or more) and reagent special grade (Fe(
NO3)+・9)1z099.0% or more] of ferric nitrate (B component compound) 20.20g was dissolved in pure water,
It was made into a light color aqueous solution of 0Th1. This aqueous solution was gradually dropped into 800 u of 4N ammonia water while stirring to form a coprecipitate.

While continuing to stir further, add niobium pentoxide powder (component B compound and component X compound) having an average particle size of 0.65 μ; 6.
After gradually adding 64 g, the precipitate was filtered and washed with pure water.

Next, after drying at 120°C for 1 hour, it was calcined at 750°C for 2 hours to obtain a raw material powder having a composition of Pb(Feo4·Nbo,s)03, which was pulverized in a ball mill.

As a result of observing this powder with a scanning electron microscope, it was found that approximately 0
．． It has a uniform particle size of 3 μ and β cos by X-ray diffraction method.
As a result of plotting the relationship between θ and sin θ (where β represents the half width of the diffraction line and θ represents the Black angle), the horizontal axis (si
It was confirmed that the crystals were almost parallel to the nθ axis) and had a uniform composition with almost no compositional fluctuations.

Also, 1.5t/c++ of this powder! As a result, a PEN solid solution having a density of 7.1, which is almost equal to the theoretical density (7,3), was obtained as a result of sintering at 1050''C for 2 hours in a lead vapor and oxygen atmosphere.

Comparative Example 1 Commercially available reagent grade pbo, FezO:+ and Nb205
Pb (Feo, 5・Nbo, s ) (h) powder was mixed in a ball mill, calcined at 750°C for 2 hours, cooled, and ground again in a ball mill.The obtained powder βcos θ~si by XvA diffraction method per
As a result of plotting the nθ relationship, significant compositional variations were observed. Furthermore, when this powder was molded and sintered in the same manner as in Example 1, the density was 6.2, which was significantly different from the theoretical density.

Example 2 33.12 g of the above reagent grade lead nitrate and 40.40 g of reagent grade ferric nitrate were dissolved in pure water to form a light brown aqueous solution of 1200 g. This aqueous solution was gradually added dropwise to 800 g of 4N ammonia water while stirring to form a coprecipitate.

Further, while stirring was continued, 7.70 g of tungsten trioxide powder having an average particle size of 0.9 μm was gradually added, and the precipitate was filtered and washed with pure water.

Next, 1) After drying at 0°C for 1 hour, calcining at 700°C for 12 hours to produce Pb(Fezz:+'”#+/l)O:+
A raw material powder of the following composition was obtained and ground in a ball mill.

This powder had a uniform particle size of about 0.5 μm, and was confirmed by X-ray diffraction to have a uniform composition with almost no compositional fluctuations.

In addition, this powder was molded at 1,5t/cnl and sintered at 880℃ for 2 hours in a lead vapor and oxygen atmosphere.
The density was 7.5, and a PFW solid solution almost equal to the theoretical density (7,6) was obtained.

Comparative Example 2 Commercially available reagent grade PbO, FezO:+, and Woe powders were blended to have a composition of Pb(Fezzz HW+, z+)Os, mixed in a ball mill, calcined at 700°C for 2 hours, and cooled. After that, it was ground again in a ball mill. According to the X-ray diffraction method, this powder showed significant compositional fluctuations.

Furthermore, when this powder was molded and sintered in the same manner as in Example 2, the density was 6.4, which was significantly different from the theoretical density.

Procedural amendments Commissioner of the Patent Office Black 1) Akio Yu 1, Indication of the case 1985 Patent Application No. 289702
Relationship with No. 3 and 7i Correction Cases Applicant Name Yudo Goto Director, Institute of Inorganic Materials, Science and Technology Agency
(332) Dainippon Toyo Co., Ltd. 4. Agent 5. Date of amendment order. 6. Subject of Uramasa. Detailed explanation of the invention in the specification. In the detailed description of the amendments, the errors in the following places will be corrected.

Claims (4)

[Claims] (1) General formula ABO_3 (where A represents one or more types of oxygen 12-coordinated metal elements, B represents one or more types of oxygen 6-coordinated metal elements, and the number of A components and B components The sum of 3 or more types of perovskites is 3 or more.) In the method for producing raw material powders of perovskites and solid solutions thereof shown in After forming a precipitate using a forming solution and then mixing the removed component compounds with the suspension, the obtained precipitate was heated to 120
A method for producing easily sinterable perovskite and its solid solution raw material powder, characterized by drying and calcining at ~1200°C. (2) the A component is lead, the B component is iron or zinc,
The method for producing easily sinterable perovskite and its solid solution raw material powder according to claim 1, wherein the removed component is niobium, tantalum, or tungsten. (3) The method for producing easily sinterable perovskite and its solid solution raw material powder according to claim (2), wherein the removed component compound is an oxide of niobium, tantalum, or tungsten. (4) A method for producing an easily sinterable perovskite and its solid solution raw material powder according to claim (2) or (3), wherein the raw material powder is used for a ceramic capacitor dielectric.