JPH06316414A - Production of perovskite type compound powder - Google Patents

Abstract

PURPOSE:To simply and easily improve dispersibility, packing ratio, dielectric property and piezoelectric property by pulverizing a perovskite type compound with a compacting pulverizer. CONSTITUTION:A water based suspension (C) is obtained by mixing a hydrated oxide (A) of one or more kind of an element selected from Ba, Pb, Sr, Mg and Ca with a hydrated oxide (B) of one or more kind of an element selected from Ti, Zr, Hf and Sn having >=50m<2>/g specific surface area so as to be (1.1-2.0):1 in mol ratio of component (A):component (B). Next, the perovskite type compound (D) is obtained by hydrothermal treating the component (C) at 100-250 deg.C, classifying the obtained product and drying. Next, the component (D) is pulverized with the compacting pulverizer. If necessary, the component (D) is calcined at 100-700 deg.C before or after pulverizing to produce the perovskite type compound powder.

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 perovskite type compound powder.

[0002]

2. Description of the Related Art A perovskite type compound has a chemical formula R
A compound having a perovskite type crystal structure found in the complex oxide represented by MX ₃ , and examples thereof include barium titanate, strontium titanate, lead titanate,
Examples thereof include lead zirconate, lead zirconate titanate, and calcium stannate. A sintered body obtained by sintering a perovskite-type compound has excellent dielectric properties, piezoelectric properties, and semiconductivity. Therefore, it is a material for electric / electronic industries such as capacitors, radio wave filters, ignition elements, thermistors. It is a useful substance.

To produce a perovskite type compound,
So-called solid phase synthesis method in which oxides and carbonates of each element are mixed and baked, oxalates of each element are synthesized in an aqueous system, or oxalates of each element are mixed in a solid phase, and then baked The so-called oxalate method, the so-called hydrothermal synthesis method in which an aqueous solution of each element and an alkaline aqueous solution are mixed, hydrothermally treated, filtered, washed and dried. The perovskite type compound thus obtained is usually crushed or pulverized into a powder, and the powder is mixed with a binder, and then a powder layer is formed on the substrate by a method such as a sheet molding method or a printing method. And then sintered to obtain a sintered body.

[0004]

With the recent miniaturization, weight reduction, high performance, and multi-functionalization of electric and electronic devices, performance requirements for parts and raw materials constituting the same have become more severe. For example, a multilayer capacitor used in an integrated circuit of a computer or the like has a structure in which a thin layer of a sintered body of a perovskite type compound and many internal electrodes are alternately stacked and electrically connected in parallel. With the demand for miniaturization and high capacity of this multilayer capacitor, further thinning of the sintered body and higher permittivity are further demanded. Therefore, the perovskite type compound powder which is the raw material of the sintered body is required. The trends toward finer particles, homogenization, and higher dispersion are becoming more and more prominent. In addition, there are strong demands for price reductions of parts and raw materials. For example, noble metal materials such as platinum, palladium, and silver were used for the internal electrodes of the above-mentioned multilayer capacitors, but cheaper base metal materials such as copper and nickel were used. Is being changed. Along with this, it is desired that the perovskite-type compound powder can be sintered at a lower temperature and has non-reducing property that does not become a semiconductor even when sintered in an atmosphere of low oxygen partial pressure.

In response to such demands, an improved method for producing perovskite type compound powder which is a raw material for the sintered body has been proposed. Taking barium titanate powder as an example, barium hydrated oxide and titanium hydrated oxide are used as raw materials, and both are mixed at a predetermined Ba / Ti molar ratio, and then a predetermined alkali concentration is obtained. The so-called hydrothermal method is well known in which hydrothermal treatment is performed under normal pressure or pressure, and the obtained product is filtered, washed, dried, and crushed. The barium titanate powder thus obtained is finer than that of the above-mentioned prior art and has a homogeneous composition. However, if the perovskite type compound powder is made into fine particles, the oil absorption is high and the dispersibility in the binder is deteriorated. Therefore, it is necessary to increase the amount of the binder to be used. As a result, the filling rate of the perovskite type compound in the obtained sintered body becomes low, and the characteristics such as dielectric property and piezoelectric property deteriorate. In addition, since the perovskite type compound powder produced by a water system such as the hydrothermal method contains a large amount of water in the perovskite type crystal structure, the properties such as dielectric properties and piezoelectricity when formed into a sintered body are particularly high. Is not enough.
As described above, it is difficult to obtain the desired perovskite type compound powder by any method under the present circumstances.

[0006]

As a result of various studies to solve the above problems, the inventors of the present invention have found that (1) when a perovskite compound is pulverized, the dispersibility in a binder is improved by using a specific pulverizer. Can be improved (2)
The perovskite-type compound powder thus obtained has excellent properties such as dielectric properties and piezoelectricity when formed into a sintered body, (3) in the hydrothermal method of the above-mentioned prior art,
A perovskite compound powder obtained by using a fine hydrated oxide having a specific specific surface area is pulverized by using the specific pulverizer of (1) above to obtain fine perovskite compound powder having good dispersibility. And (4) firing the perovskite-type compound before or after crushing the perovskite-type compound, water in the perovskite-type crystal structure can be removed, and the dielectric and piezoelectric properties of the sintered body can be improved. The inventors have completed the present invention by discovering that properties such as properties can be further improved.

That is, the present invention is to provide a perovskite type compound powder having excellent dispersibility in a binder.

The present invention is a method of using a consolidation crusher as a crusher when crushing a perovskite type compound. A compaction pulverizer is a pulverizer having both a compression action and an attrition action, and when a perovskite type compound is put into the consolidation pulverizer and pulverized, it is compacted into flakes by the compression action, and at the same time, it is pulverized. It is finely crushed by the crushing action. As the compaction crusher, for example, a crusher, an edge runner, a roller mill or a fret mill can be used.

In the present invention, various compounds can be used as the perovskite type compound, and examples thereof include barium titanate, strontium titanate, lead titanate, lead zirconate, lead zirconate titanate and calcium stannate. Used. These perovskite type compounds are generally produced by conventional methods such as the so-called solid phase synthesis method, oxalate method, hydrothermal synthesis method, hydrothermal method and the like. In the present invention, it is particularly preferable to use a perovskite type compound obtained by the following method in which a fine hydrated oxide having a specific specific surface area is used as a raw material in the hydrothermal method.

Next, a preferred method for producing the perovskite type compound used in the present invention will be described in detail. In a so-called hydrothermal method, an aqueous suspension containing various hydrated oxides is hydrothermally treated to obtain a perovskite type compound. In the present invention, Ba, Pb, Sr, Mg and C are used.
a hydrated oxide of at least one element selected from a,
Specific surface area of 50 m ² / g or more, preferably 80 m ² / g
The above-mentioned aqueous suspension comprising a hydrated oxide of at least one element selected from Ti, Zr, Hf and Sn is hydrothermally treated.

In the present invention, the hydrated oxide includes so-called hydrated oxide, as well as oxide, hydrous oxide and hydroxide. As the hydrated oxide of at least one element selected from Ba, Pb, Sr, Mg and Ca, a commercially available product may be used, but for example, an aqueous solution of a water-soluble salt such as chloride, nitrate or acetate of the element. It is preferable to use a product obtained by adding an alkali to and neutralizing. . The other raw material, Ti, Zr, having a specific surface area of 50 m ² / g or more,
The hydrated oxide of at least one element selected from Hf and Sn is, for example, neutralized by adding an alkali to an aqueous solution of a water-soluble salt such as chloride, nitrate or acetate of the element, or the water-soluble salt. It is obtained by hydrolyzing a salt at a temperature of 70 ° C. or higher. The specific surface area of the hydrated oxide is 50 m ² /
When it is smaller than g, it is difficult to obtain a fine particle perovskite type compound, and it is difficult to obtain a compound having a large amount of impurities and a uniform component composition.
It is not preferable from an industrial viewpoint that the temperature of the hydrothermal treatment needs to be increased or the treatment time needs to be lengthened. The hydrated oxide obtained by the above-mentioned neutralization or hydrolysis is preferably filtered and washed to remove impurities.

Next, a hydrated oxide of at least one element selected from Ba, Pb, Sr, Mg and Ca and a hydrated oxide of at least one element selected from Ti, Zr, Hf and Sn. Is suspended in water to prepare an aqueous suspension. The hydrated oxide of at least one element selected from Ba, Pb, Sr, Mg and Ca is T
The hydrated oxide of at least one element selected from i, Zr, Hf and Sn is mixed in a molar ratio of preferably 1 or more, particularly preferably 1.1 to 2.0. When the above molar ratio is less than 1, a perovskite type compound having a desired composition cannot be obtained, or a surplus component is likely to remain in the perovskite type compound, which tends to impair properties such as dielectric properties and piezoelectricity, which is not preferable. . Next, the aqueous suspension is hydrothermally treated at a temperature of preferably 80 ° C or higher, particularly preferably 100 to 250 ° C. When the temperature of the hydrothermal treatment is lower than 80 ° C., the reaction rate is slow, the hydrothermal treatment requires a long time, and unreacted substances tend to remain in the perovskite type compound, which is not preferable. The hydrothermal treatment is usually carried out preferably at a saturated vapor pressure, but may be pressurized to a saturated vapor pressure or higher, or at atmospheric pressure. The hydrothermal treatment can be carried out by a heat and pressure resistant device which is usually used industrially.

The product thus obtained is separated by a conventional method, washed if necessary, and dried to obtain a perovskite type compound. The drying can be performed at any temperature, but a temperature of 80 to 150 ° C is suitable. The perovskite type compound thus obtained is pulverized by the above-mentioned compaction pulverizer to obtain the perovskite type compound powder of the present invention.

In the present invention, a perovskite type compound, particularly a perovskite type compound produced in an aqueous system such as a hydrothermal method, is crushed by a compaction crusher or after crushing,
It is desirable to calcine the perovskite type compound at a temperature of 100 to 700 ° C.

[0015]

【Example】

Example 1 1 liter of a 2.5 mol / l titanium tetrachloride aqueous solution in terms of TiO ₂ and 1 liter of ion-exchanged water were placed in a 5-liter four-necked flask while being cooled with ice. With stirring, 28% aqueous ammonia solution was added dropwise until the pH of the liquid became 7. The obtained precipitate of hydrated titanium oxide was filtered with a suction filter and washed until the conductivity of the filtrate became 20 μS / cm to obtain a filter cake. A part of this filter cake was dried at a temperature of 105 ° C. and its specific surface area (BET method) was measured, and it was 300 m ² / g. Next, an amount of 100 g in terms of TiO ₂ was collected from the above filter cake, and this filter cake and 1 liter of deionized water were placed in a beaker to obtain an aqueous suspension. Then, this aqueous suspension and commercially available barium hydroxide (Ba (OH) ₂ .8H
_After 592 g of ₂ O) (Ba / Ti molar ratio = 1.5) was placed in a 3 liter autoclave, the mixture was heated and kept at a temperature of 150 ° C. for 1 hour for hydrothermal treatment under a saturated steam pressure. The product obtained was then filtered on a suction filter, washed and dried at a temperature of 105 ° C. Obtained dried product 10
g was crushed for 30 minutes by a crusher to obtain barium titanate powder (Sample A) of the present invention.

Example 2 10 g of the dried product obtained in Example 1 was calcined at a temperature of 550 ° C. for 1 hour, and then pulverized with a crusher for 30 minutes to obtain the barium titanate powder (sample B) of the present invention. Obtained.

Comparative Example 1 10 g of the dried product obtained in Example 1 was hand crushed to obtain a comparative sample C.
And

Sample A obtained in the above Examples and Comparative Examples
Oil absorption and relative dielectric constant of the sintered body at 1200 ° C.
Table 1 shows the results of measuring the dielectric loss by a conventional method. The relative permittivity and the dielectric loss were measured at 1 KHz using an LCR meter at room temperature. As a result of chemical analysis of the comparative sample C, the Ba content was 55.3% by weight and the Ti content was 20.
3 wt%, Na content 0.002 wt%, Ba
The molar ratio of / Ti was 0.950. The specific surface area (BET method) of this comparative sample C was 11.0 m ² / g, and the particle size was 0.15 μm. As a result of X-ray diffraction, Comparative Sample C was cubic barium titanate. The specific surface area (BET method) and particle size of Samples A and B are comparable to those of Comparative Sample C, and Samples A and B
Was the same cubic barium titanate as Comparative Sample C.

[0019]

[Table 1]

Example 3 20 ml of a 2.5 mol / l titanium tetrachloride aqueous solution in terms of TiO ₂ , 52 ml of a 1 mol / l zirconium oxychloride aqueous solution and 300 ml of ion-exchanged water were placed in a 5-liter four-necked flask. . A 10N aqueous sodium hydroxide solution was added dropwise until the pH of this solution reached 7. In addition, a part of the obtained precipitate was collected, filtered with a suction filter, washed, and dried at a temperature of 105 ° C. to obtain a specific surface area (BE
It was 200 m < ² > / g when the T method) was measured. Next, 105 ml of a 1 mol / l lead nitrate aqueous solution was added to the above-mentioned precipitation-produced solution under stirring, and 10 N sodium hydroxide aqueous solution was added dropwise until the pH of the solution became 7, and then 10 N sodium hydroxide was added. 25 ml of an aqueous solution and ion-exchanged water were added dropwise to obtain an aqueous suspension having a total liquid volume of 1 liter. The molar ratio (addition amount) of Pb: Zr: Ti is 1.0.
It was 5: 0.52: 0.50. Then, the aqueous suspension was put into a 3 liter autoclave, heated, and kept at a temperature of 200 ° C. for 0.5 hours to carry out hydrothermal treatment under a saturated steam pressure. The product obtained is filtered on a suction filter, washed and dried at a temperature of 105 ° C. Then
10 g of the obtained dried product was pulverized with a crusher for 30 minutes to obtain a lead zirconate titanate powder (Sample D) of the present invention.

Example 4 10 g of the dried product obtained in Example 3 was calcined at a temperature of 350 ° C. for 1 hour, and then pulverized with a crusher for 30 minutes to obtain the lead zirconate titanate powder of the present invention (Sample E). ) Got.

Comparative Example 2 10 g of the dried product obtained in Example 3 was hand ground to obtain a comparative sample F.
And

As a result of chemical analysis of the comparative sample F, the Pb content was 64.5% by weight, the Zr content was 14.0% by weight, and the T
The i content was 7.5% by weight, the Na content was 0.008% by weight, and the molar ratio of Pb: Zr: Ti was 1.00: 0.
It was 49: 0.50. The specific surface area of this comparative sample F was 8.9 m ² / g, and the particle size was 0.5 μm. As a result of X-ray diffraction, the comparative sample F was cubic lead zirconate titanate. The specific surface area (BET method) and particle size of Samples D and E are similar to those of Comparative Sample F, and Samples D and E are the same cubic zirconate titanate as Comparative Sample F. It was lead acid. The oil absorptions of Samples D to F obtained in the above Examples and Comparative Examples, the sintering temperatures of Samples D to F and commercially available lead zirconate titanate powder, and the particle sizes at those sintering temperatures were determined by a conventional method. Table 2 shows the measurement results
Shown in.

[0024]

[Table 2]

[0025]

INDUSTRIAL APPLICABILITY The present invention is a method for producing a perovskite type compound powder in which a perovskite type compound is crushed using a compaction crusher, and the dispersibility in a binder is improved to obtain a sintered body. This is an industrially useful method in which the filling rate at that time can be increased, and the characteristics such as dielectric properties and piezoelectricity can be easily and easily improved. Desirable method of the present invention, in the hydrothermal method of the prior art, a method of pulverizing a perovskite compound obtained by using a fine hydrated oxide having a specific specific surface area using a compaction pulverizer, or Before or after compaction pulverization of the perovskite-type compound, the perovskite-type compound is calcined at a temperature of 100 to 700 ° C. By these methods, fine particles of perovskite having a low content of impurities and good dispersibility in a binder are obtained. A type compound powder is obtained, which is excellent in low-temperature sinterability and can improve properties such as dielectric properties and piezoelectricity when a sintered body is formed.

Claims (3)

[Claims] 1. A method for producing a perovskite type compound powder, which comprises pulverizing a perovskite type compound with a compaction pulverizer. 2. A hydrated oxide of at least one element selected from Ba, Pb, Sr, Mg and Ca, and at least one selected from Ti, Zr, Hf and Sn having a specific surface area of 50 m ² / g or more. A method for producing a perovskite-type compound powder, characterized in that a perovskite-type compound obtained by hydrothermally treating an aqueous suspension comprising a hydrated oxide of the element is pulverized with a compaction pulverizer. 3. A method for producing a perovskite type compound powder, which comprises firing the perovskite type compound at a temperature of 100 to 700 ° C. before or after the pulverization according to claim 1 or 2.