JPH0328109A - Production of compound oxide powder - Google Patents

Abstract

PURPOSE:To obtain compound oxide powder having a composition of excellent uniformity by heat-treating at a given temperature a precursor for producing a uniform compound oxide comprising a thermally decomposable metallic compound, sol of metal oxide, etc., as raw materials. CONSTITUTION:Plural compounds are selected from a thermally decomposable metallic compound, sol of metal oxide and sol of metal hydroxide. A solution containing the plural compounds and a solvent is blended with a water-soluble polymer compound. Then the solvent is removed from the mixed solution to give a precursor for producing a compound oxide. Then the precursor is heat- treated at >=400 deg.C.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a precursor for producing a complex oxide, and a method for producing a complex oxide powder having a fine and uniform composition using this precursor. .

Composite oxide powders have many uses including dielectrics, piezoelectrics, superconductors, electronic component materials such as optoelectronic materials, and catalysts. In recent years, there has been a demand for higher functionality of these materials, and raw material powders are also required to have low-temperature sinterability, uniform composition, and the like. The present invention meets these needs.

[Prior Art] Conventionally, the following method is known as a method for producing composite oxide powder.

(1) Dry method This method uses raw material compounds (mainly oxides) as constituent components.
This method involves dry mixing or wet mixing and firing the mixture. This method has advantages such as the raw material powder is inexpensive and does not require complicated operations, but it has problems such as difficulty in obtaining raw material powder with a uniform composition and the possibility of contamination with impurities during mixing. . Furthermore, in order to obtain a composite oxide powder with a uniform phase using this method, it is necessary to increase the sintering temperature, which causes the particles of the raw material powder to become coarse.

(2) Co-precipitation method In this method, a mixed solution is prepared by mixing all of the components, a precipitating agent such as an alkali is added to this solution to coprecipitate the components, and this coprecipitate is filtered. , drying and firing. In this coprecipitation method, a fine raw material powder can be obtained, but the precipitate formation state of each metal ion often differs depending on the PL1 of the solution when the precipitant is added, and the composition of the produced oxide may vary. However, there are drawbacks such as the fact that the composition is often different from the initially set composition and it is difficult to obtain the desired composite oxide.

(3) Alkoxide method This method utilizes the production of a metal oxide or hydroxide coprecipitate and alcohol by hydrolyzing a mixture of alkoxide solutions of certain components.

The oxide powder obtained by this method is very fine;
Since the particle size distribution is narrow and the purity is high, the powder obtained by this method has excellent characteristics as a ceramic raw material powder.

However, the alkoxide raw material is expensive, and the solvent must be sufficiently dehydrated to prepare the alkoxide solution, resulting in dehydration costs and solvent recovery costs.

[Problems to be Solved by the Invention] An object of the present invention is to improve the drawbacks of conventional methods for producing composite oxide powder, and to provide a composite oxide powder precursor with excellent compositional uniformity, fineness, and good sinterability. An object of the present invention is to provide a method for producing a composite oxide powder using the precursor and a method for producing a composite oxide powder using the precursor.

[Means to solve the problem] There are many types of composite oxides depending on their crystal structure.

For example, those having a ferromagnetic Subinel structure, a magnetoplumbite structure, a ferroelectric Belobusite structure, etc. are well known.

In order to produce composite oxide powder with excellent compositional uniformity, it is necessary to uniformly mix various metal raw materials.

Such an ideal mixed state can be obtained, for example, by uniformly dissolving various metal compounds in a common solvent. It is believed that in solutions in which various metal salts are dissolved, mixing occurs on the atomic order, and in solutions in which various colloidal solutions are mixed, mixing occurs on the colloidal order. It is believed that by removing the solvent while maintaining such a mixed state and firing the obtained components, it is possible to prepare a composite oxide powder with excellent compositional uniformity at a low temperature. For example, in the coprecipitation method, which is a conventional technique, a precipitant is added to a precipitate in which various metal compounds are dissolved and mixed in a common solvent to obtain a precipitate in which various metal components are mixed. The conditions for precipitating a certain amount of metal differ depending on the metal component, and generally it is practically impossible to precipitate a large number of ions at the same time.

In addition, when the solvent is removed from a solution in which various metal components are dissolved and mixed by evaporation to dryness or spray drying, segregation of the metal components during drying is avoided because the solubility of the various metal components in the solvent is different. I can't. When attempting to prepare a composite oxide powder by firing the precursor obtained as described above, if the composition of the precursor is non-uniform and an attempt is made to obtain a single composite oxide phase, high sintering or Requires temperature.

In order to solve the above-mentioned problems, the inventors of the present invention have investigated the results of their research, and found that a solution obtained by removing the solvent from a solution in which various metal compounds are dissolved and mixed under certain conditions is a homogeneous solution. The present invention was completed by discovering that a precursor for producing composite oxide powder having the following composition could be obtained. That is, the present invention mixes a water-soluble polymer compound with a solution containing two or more compounds and a solvent selected from the compound group of thermally decomposable metal compounds, metal oxide sols, and metal hydroxide sols, This invention relates to a method for producing a precursor for producing a composite oxide, characterized by removing the solvent from the mixed solution, and further characterized by heat-treating the precursor obtained by this method at a temperature of 400°C or higher. The present invention relates to a method for producing composite oxide powder.

Next, the present invention will be explained in further detail.

The composite oxide obtained in the present invention is not particularly limited, and for example, any composite oxide having a spinel structure or magnetoplumbite structure with ferromagnetism, a belobus-powerite structure with ferroelectricity, etc. can be obtained. However, it is particularly effective for producing perovskite complex oxides.

The present invention will be explained in detail below using as an example a method for obtaining a composite oxide having a perovskite structure.

A belobusite-type composite oxide is generally represented by ABO3. There are many combinations of the A component and the B component in the general formula that have such a bellows power structure. For example, in a material used as a capacitor material, the A component is Pb, Pb,
It is known that the B component consists of TI, Mg, N1, and Nb, and the following compositions are known.

[PbTiO i co - - [Pb
(Mg+, 3 Nb 2zi ) 0 3
] −[Pb (Nll/3 Nb 2/x
) 0 3 ko 2 ( :.:. teX+Y+Z-
(hereinafter abbreviated as PT-PMN-PNN) In the present invention, the raw materials for preparing the precursor for producing a composite oxide include compounds such as thermally decomposable metal compounds, metal oxide sols, and metal hydroxide sols. Two or more compounds of the group are used. Specific thermally decomposable metal compounds include:
Examples include carboxylates and nitrates of various metals. Among these metal elements such as TI and ZrSNb, it is difficult to use carboxylates, nitrates, etc., so it is preferable to use metal oxide sol or metal hydroxide sol. Metal oxide sols and metal hydroxide sols include those obtained by ultrafinely pulverizing metal oxides and metal hydroxides using a ball mill or vibration mill and dispersing them in a solvent, commercially available various metal oxide colloidal solutions, or It is possible to use sol obtained by preparing various metal alkoxides, metal chlorides, metal oxychlorides, metal oxalic acid compounds, etc. through reactions such as hydrolysis, but when metal chlorides etc. are used as raw materials, Chlorine ions and the like remaining in the production system cause a decline in the performance of the product powder, and also combine with other raw materials, such as PB, to form precipitates, so it is necessary to prepare the product sufficiently. In addition, chloride ions and oxalate ions can be used with other raw materials such as p
In order to combine with b and form a precipitate, sufficient purification is required when a sol is prepared using raw materials containing these. The particle size of the sol used here is 500n or less, especially 100r+, since the smaller the particle size, the more reactive it is.
It is preferable to use sol particles of +w or less. In the production of the velocytite complex oxide having the composition PT-PMN-PNN shown above, Pb, Mg, N1
can be made from acetate or nitrate, and TISNb can be made from sol.

Next, such raw materials are dissolved and mixed using a solvent. The solvent used here is not particularly limited, but it is necessary to select a solvent and conditions that will dissolve all the thermally decomposable metal compounds, and if a sol is used, the sol particles will not aggregate or gel. be. Water is the most suitable solvent that satisfies these conditions, and is also optimal in terms of cost, but it is not limited to water. For example, water and alcohol, or water and organic acids (formic acid, acetic acid, etc.) A mixed solvent or a non-aqueous solvent may be used. In addition, for example, when using titania sol as part of the raw material, it is necessary to maintain conditions that do not cause the solvent to gel, that is, pl1 is 4 or less, and the same precautions are required when using sols with other metal components. be.

When the raw materials are melted and mixed, the various metal components are uniformly mixed on the atomic or colloidal order. By removing the solvent and firing while maintaining such a mixed state, a composite oxide powder with a narrow particle size distribution can be prepared at a low temperature.

In the present invention, it is essential to mix the water-soluble polymer compound into the mixed solution before removing the solvent from the dissolved and mixed solution.

The effect of the water-soluble polymer compound used here is not clear, but when the solvent is removed from the solution in which various metal components are dissolved and mixed, metal ions are present in the network formed by the water-soluble polymer compound. Alternatively, it is considered that the incorporation of colloidal particles suppresses segregation of various metal salts or aggregation of colloidal particles, making it possible to remove the solvent from the mixed solution while maintaining an ideal mixed state. Therefore, in the present invention, the water-soluble polymer compound is not particularly limited, but when the solvent is removed from the solution in which various metal components are dissolved and mixed, the polarization of the metal salt and the colloid. Particularly preferred are materials that are considered to have a strong particle aggregation prevention effect, such as polyvinyl alcohol, polyethylene glycol, polyacrylic acid, and polymethacrylic acid.

The method of adding such a water-soluble polymer compound is not particularly specified, and the water-soluble polymer compound may be added to a mixed solution of various metal compounds, or various metal compounds may be added to a water-soluble polymer solution. They may also be mixed. If the amount of the water-soluble polymer compound used is small, the effect of preventing segregation or aggregation will not be exhibited. Therefore, the amount of water-soluble polymer compound added varies depending on the type of metal component, but
20 wt% or more of the weight of the metal oxide, preferably 50 wt%
The amount is such that it is equal to or higher than vt%.

The method for removing the solvent from the solution containing the various components as described above is not particularly limited, but ordinary evaporation to dryness, spray drying, etc. can be used. When performing evaporation to dryness, it is preferably performed under stirring, and may also be performed under reduced pressure.

A precursor for producing a composite oxide can be obtained by the method described above.

Next, a method for obtaining composite oxide powder from the obtained composite oxide production precursor will be described.

In the present invention, the obtained precursor is heat-treated at a temperature of 400° C. or higher, but it is preferable that the precursor is first subjected to thermal decomposition at a relatively low temperature. This is preferable in that by-product gases generated during the heat treatment are first removed by thermal decomposition and then fired at a high temperature. The thermal decomposition temperature at this time is 250°C or higher, preferably 300°C or higher. If this temperature is less than 250° C., the arc arc q of the precursor will not progress sufficiently. Although the time required for minute angle A varies depending on the amount of the water-soluble polymer compound added, it is sufficient to carry out the reaction in an air atmosphere for about one hour. The pyrolyzed precursor is then incinerated. This sintering step does not need to be strictly separated from the pyrolysis step, and sintering may be carried out following pyrolysis, or may be carried out after the pyrolyzed precursor is once pulverized with a ball mill or the like. . The firing temperature varies greatly depending on the crystal structure of the target composite oxide and ease of production, but is usually 4.
00°C or higher is required. If the firing temperature is less than 400° C., it is not preferable because it is difficult to obtain the desired composite oxide and carbon produced by decomposition of the water-soluble polymer compound may remain. For example, in the case of producing a belobusite type composite oxide, the firing temperature may be 600°C or higher, preferably 700 to 900°C.

In the present invention, of course, heat treatment including decomposition and firing may be performed at a temperature of 400° C. or higher from the beginning.

The effect of using a water-soluble polymer in the present invention is to suppress polarization of various metal salts or aggregation of colloidal particles,
It not only makes it possible to remove the solvent from the mixed solution while maintaining the ideal mixing state, but also has the effect of refining the composite oxide powder prepared by thermally decomposing the precursor and then firing it. There is. Although the detailed mechanism is unknown, during the process of thermally decomposing the precursor and further firing, the decomposition effect of the water-soluble polymer compound that is thought to form the network acts effectively, resulting in the formation of complex oxidation. It is thought that a very fine powder with a uniform particle size distribution can be obtained.

The primary particle size of the composite oxide powder obtained in the present invention varies depending on the type and amount of the water-soluble polymer used and the decomposition and firing conditions, but it is usually 1 μm or less. Also,
The particle size can be controlled to some extent by the amount of the polymer compound added, and the larger the amount added, the smaller the primary particle size of the resulting powder tends to be.

[Effects of the Invention] As is clear from the above description, according to the present invention, a uniform precursor composition can be prepared using a thermally decomposable metal compound, metal oxide sol, or metal hydroxide sol as raw materials, and By thermally decomposing the body composition and firing it, a composite oxide with excellent compositional uniformity can be prepared. Furthermore, due to the decomposition of the water-soluble polymer compound used to prepare the uniform precursor composite, a very fine composite oxide powder can be obtained.

[Example code] Next, the present invention will be explained in more detail with reference to Examples.

Example 1 (1-1) Perobus force type Pb (Mg+.2i N
b2/3) 03? Preparation of precursor for powder production In a 200rd fourth flask equipped with a stirrer, add 5.89 g of lead acetate trihydrate, 1.07 g of magnesium acetate tetrahydrate, and 2.6 g of polyethylene glycol (average molecular weight m6000).
4 g of distilled water and 80 g of distilled water were added and dissolved with stirring. A solution of 3.18 g of niobium pentaethoxide in 25 ml of absolute ethanol was added to 80 ml of distilled water to prepare a niobium sol. This diobium sol was added to and mixed with the previously prepared lead and magnesium solution by stirring and pressing. This mixed solution was heated using an oil bath and evaporated to dryness. Although the viscosity of the solution increased as evaporation progressed, no aggregation of niobium sol or segregation of salts was observed.

(1-2) Perobus force type Pb (Mg+/s Nb
2. (3) Preparation of 03 powder The resinous precursor obtained by the above procedure was transferred to a magnetic crucible and thermally decomposed in air at 300°C using a Matsufuru furnace.

The obtained sample was ground in a ball mill for 1 hour, then transferred to a magnetic boat and fired for 2 hours at 850° C. under air circulation using a tubular furnace. The resulting powder? When analyzed using X-ray diffraction, a peak indicating the Pb(Mg1/, Nb273)03 belobite phase and a peak indicating the presence of a trace amount of pyrochlore phase (peak intensity ratio of the strongest peak is less than 1/10)
was observed. In addition, when the shape of the particles was observed using a scanning electron microscope (SEM), the average particle diameter was 0.8 μm.
m primary particles and their weakly aggregated secondary particles were observed.

Example 2 (2-1) Beloved type Pb (Mg+/3Nb2z
3) 0> Preparation of precursor for powder production As a niobium sol, Eiwa niobium oxide (surface area 14011
12/g. Using a niobium sol prepared by finely pulverizing ignition loss 15.9%) in water using a vibrating mill using zirconia beads for 24 hours to finely pulverize it to an average particle size of 0.2 μ flaws. The same operation as in Example 1 (1-1) was performed except that No sol aggregation and salt polarization were observed during precursor preparation.

(2-2) Belobus-type Pb (MglJb2/i
) Preparation of Oi powder (2-1) The precursor obtained in Example 1 (1-2)
When the powder obtained by performing the same operation as above was analyzed using X-ray diffraction, it was found that Pb(Mg+/i Nb2/i)03
A peak indicating the belobus pyrite phase and a peak indicating the presence of a trace amount of pyrochlore phase (the peak intensity ratio of the strongest peak is about 1
1) was observed. In addition, when the shape of the particles was observed using a scanning electron microscope, the average particle diameter was 0.8 μm.
m primary particles and their weakly aggregated secondary particles were observed.

Example 3 (3-1) Perovskite type 0.2PTO-0.2PM
Preparation of Precursor for N-0.6PNN Powder Production 50 g of distilled water in a 200 four-necked flask equipped with a stirrer.
4.4 g of polyvinyl alcohol was added and dissolved with stirring under heating. Additionally, 5.69 g of lead acetate trihydrate, 0.215 g of magnesium acetate tetrahydrate, and 0.74 g of nickel acetate tetrahydrate.
7 g was added and stirred to dissolve. Niopbentaethoxide 2.
A niobium sol was prepared by dissolving 55 g of the solution in 20 bottles of absolute ethanol and adding it to 70 bottles of distilled water.

A solution of 0.684 g of titanium tetraethoxide in 15 rni of absolute ethanol was added to 1 ml of polyvinyl alcohol.
A titania sol was prepared by adding the titania sol to 40 g of a 4 wt % formic acid aqueous solution containing vL%. The niobium sol and titania sol were added to and mixed with the previously prepared lead, nickel, and magnesium solution under stirring. This mixed melt was heated using an oil bath and evaporated to dryness. Although the viscosity of the solution increased as the evaporation proceeded, no aggregation of the niobium sol and titania sol and segregation of salts were observed, and a resinous precursor was obtained at the end of the evaporation to dryness.

(3-2) Preparation of perovskite type PT-PMN-PNN powder The resinous precursor obtained by the above operation was transferred to a magnetic Lupo and thermally decomposed in air at 300°C using a Matsufuru furnace. The obtained sample was ground in a ball mill for 30 minutes, then transferred to a magnetic boat and incinerated at 850° C. for 2 hours under air circulation using a tubular furnace. When the obtained powder was analyzed using X-ray diffraction, it was found that PbTIO3: Pb(Mg+・3Nb2
/3) 03: Pb (Nl+,・3Nb2/
3) A peak indicative of a belobite phase in which 03 was dissolved as a solid solution and a peak indicative of the presence of a trace amount of pyrochlore phase (peak intensity ratio of the strongest peak was less than 1/IO) were observed.

In addition, when the shape of the particles was observed using a scanning electron microscope (SEM), it was found that primary particles with an average particle diameter of 0.5 μm;
and its weakly aggregated secondary particles were observed. Figure 1 shows the X-ray diffraction pattern.

Example 4 (4-1) Peropskite type 0.2PT-0.2PMN
-0. Preparation of precursor for ePNN powder production As titania sol, chloride ions contained in commercially available titania sol were removed and purified by repeating the operation of concentrating the titania sol using an ultrafiltration membrane and diluting it with an aqueous formic acid solution. A niobium sol is prepared by dissolving hydrated niobium oxide and oxalic acid dihydrate in water at 110°C, cooling it on ice, and filtering off the precipitated oxalic acid. The same operation as in Example 3 (3-1) was performed, except that the purified product was used. No sol aggregation and salt polarization were observed during precursor preparation. (4-2) Perovsky? The precursor obtained in the preparation of type PT-PMN-PNN powder (4-1) was prepared in Example 3 (3-2).
When the powder obtained by performing the same operation was analyzed using X-ray diffraction, it was found that PbTIO*: Pb
(Mg+/3Nb2/i)Oi; Pb(Ni+7i
Nb2. (2) A peak indicating a belobite phase in which Oi is solidly dissolved and a peak indicating the presence of a trace amount of pyrochlore phase (peak intensity ratio of the strongest peak is less than 1/IO) were observed. Further, when the shape of the particles was observed using a scanning electron microscope, primary particles with a flat particle diameter of 0.6 μm and weakly aggregated secondary particles thereof were observed.

Example 5 (5-1) Preparation of Precursor for Manufacturing Subinel Type Code 20 4 Complex Oxide Powder In a 100rd flask equipped with a stirrer, 2.49 g of cobalt acetate tetrahydrate, 8.08 g of iron nitrate nonahydrate, distilled water 4
0 g and 4 g of polyvinyl alcohol were added and dissolved with stirring.

This mixed solution was heated using an oil bath and evaporated to dryness. Although the viscosity of the solution increased as the evaporation progressed, no salt segregation was observed, and a resinous precursor was obtained at the end of the evaporation to dryness.

(5-2> Preparation of Subinel type COFe204 composite oxide powder The resinous precursor obtained by the above operation was transferred to a magnetic crucible and thermally decomposed in air at 300°C using a Matsufuru furnace.

The obtained sample was ground in a ball mill for 1 hour, then transferred to a magnetic boat and calcined for 2 hours at 500° C. under air circulation using a tubular furnace. When the obtained powder was analyzed using X-ray diffraction, only a peak indicating a spinel structure was observed. Furthermore, when the shape of the particles was observed using a scanning electron microscope (SEM), primary particles with an average particle diameter of 0.4 μm and weakly aggregated secondary particles thereof were observed.

Comparative Example 1 Perovskite type PT-PMN-PN by powder mixing method
Preparation of N powder Lead oxide 13.69g, Magnesium oxide 0.166g,
Nickel oxide 0.916g, titanium dioxide 0.98g,
4.3 g of niobium pentoxide was mixed for 18 hours using a ball mill. After drying the mixture, it was transferred to a magnetic boat and fired at 850° C. for 2 hours under air circulation using a tubular furnace. When the obtained powder was analyzed using X-ray diffraction, it was found that PbTI0
3; Pb CMg+/3Nb2. ) 03:
A peak indicating a belobite phase in which Pb (N11/3Nb2/3)03 is solidly dissolved and a peak indicating the presence of a large amount of pyrochlore phase (peak intensity ratio of the strongest peak 10:4)
was observed.

Comparative Example 2 Preparation of Perovskite Type PT Powder In a 200d fourth flask equipped with a stirrer, 5.89 g of lead acetate trihydrate, 1.07 g of magnesium acetate trihydrate,
80 g of distilled water was added and dissolved with stirring. Dissolve 3.18 g of niopbentaethoxide in 25 mN of absolute ethanol and add 80 mj of distilled water! was added to prepare a niobium sol. This niobium sol was added to and mixed with the previously prepared lead and Mg solution under stirring. This mixed solution was heated using an oil bath and evaporated to dryness. As evaporation to dryness progresses,
Niobium sol agglomeration and salt segregation were observed. By evaporation to dryness? The filtrated solid was transferred to a magnetic boat and calcined at 850° C. for 2 hours under air circulation using a tubular furnace. When the generated powder was analyzed using X-ray diffraction, it was found that Pb (Mg+/
3Nb2/3) 0 3 A peak indicating the berovskite phase and a peak indicating the presence of a large amount of pyrochlore phase (peak intensity ratio of the strongest peak: lo: 3) were observed.

[Brief explanation of drawings]

Figure-1 shows the X of the PT-PMN-PNN powder obtained in Example 3.
This is a glandular diffraction diagram.

Claims (1)

[Claims] 1) Mix a water-soluble polymer compound with a solution containing two or more compounds selected from the compound group of thermally decomposable metal compounds, metal oxide sol, and metal hydroxide sol and a solvent, and extract the solvent from the mixed solution. 2) A method for producing a precursor for producing a composite oxide, characterized by removing 2) 2 selected from the compound group of thermally decomposable metal compounds, metal oxide sol, and metal hydroxide sol.
A composite oxide characterized in that a precursor obtained by mixing a solution containing at least one type of compound and a solvent with a water-soluble polymer compound and removing the solvent from the mixed solution is heat-treated at a temperature of 400°C or higher. Powder manufacturing method