JPH0558632A - Production of perovskite-type multiple oxide powder - Google Patents

Abstract

PURPOSE:To provide the subject powder of fine particle size with high surface activity, narrow in particle size distribution, and uniform in composition. CONSTITUTION:The objective powder of general formula (A1-xA'x)BO3 (A is at least one kind of alkaline earth metal; A' is at least one kind of doping element selected from bismuth and lanthanide series; B is at least one kind of tetravalent metallic element; x<0 or 1). This powder can be obtained by the following method: an alkoxide of tetravalent metallic element such as titanium is added to a warm aqueous solution of (1) at least one kind of alkaline earth metal hydroxide and (2) 1-4 moles of an alkali per mol of hydroxide to produce and precipitate a basic composition of general formula ABO3 (A is at least one kind of alkaline earth metal; B is at least one kind of tetravalent metallic element) followed by addition of an alkoxide of doping element to produce and precipitate a doping element compound, and the resulting mixed precipitate is calcined.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a perovskite type complex oxide powder, particularly electroceramics,
That is, the present invention relates to a method for producing a perovskite-type composite oxide powder useful as a ceramic material such as a dielectric ceramic, a ferroelectric ceramic, a semiconductor ceramic, and a piezoelectric ceramic used in the electronic field.

[0002]

2. Description of the Related Art As a method for producing this type of perovskite type complex oxide powder, (a) an alkaline earth metal carbonate, an oxide of a tetravalent metal element, and a doping agent as a semiconductor agent or Curie point shift agent A method of mixing powders of elemental carbonates or oxides, pulverizing, calcining at a temperature of 1000 ° C. or higher, and pulverizing, and (4) adding a tetravalent solution to a warm aqueous solution of an alkaline earth metal hydroxide A method is known in which a mixed alkoxide solution containing an alkoxide of a metal element and an alkoxide of the doping element is added and reacted.

[0003]

[Problems to be Solved by the Invention] However, (a)
In the above method, since powder is used as a raw material, it is impossible to uniformly disperse at the molecular level, and it is impossible to obtain a microscopically uniform fine powder.
Since it is generated by a solid phase reaction at a high temperature of ℃ or higher,
The reaction product becomes lumpy and necessarily requires mechanical grinding. For this reason, there are problems that impurities are mixed due to abrasion of the medium during pulverization, and that only powder having poor particle size distribution and low surface activity can be obtained.

On the other hand, in the method (b), in order to form a solid solution of the semiconducting agent and the Curie point shift agent, a reflux operation or a chelating agent is added to form a composite. There is a problem that the doping element that should be solid-dissolved in the A site is dissolved in the B site by the operation, and an electroceramic having desired characteristics cannot be obtained.

Therefore, an object of the present invention is to obtain a perovskite type complex oxide powder having a fine particle size, high surface activity, and a narrow particle size distribution and a uniform composition.

[0006]

SUMMARY OF THE INVENTION The present invention provides, as means for solving the above problems, the general _{formula: (A 1-x A '} x) BO 3,
(In the formula, A represents at least one alkaline earth metal, A ′ represents at least one doping element selected from the group consisting of bismuth and lanthanum series elements, B represents at least one tetravalent metal element, and x <0. In the production method of the perovskite type complex oxide powder represented by
A alkoxide of a tetravalent metal element is added to a warm aqueous solution obtained by dissolving at least one hydroxide of an alkaline earth metal and 1 to 4 mol of alkali corresponding to the hydroxide to give a general formula:
After the basic composition represented by ABO ₃ (wherein A represents at least one alkaline earth metal and B represents at least one tetravalent metal element) is formed and precipitated, an alkoxide of a doping element is added. The doping element compound is produced and precipitated by roasting the obtained mixed precipitate.

As the alkaline earth metal, Ba, S
Examples thereof include r, Mg and Ca, and these may be used alone or in combination of two or more depending on the intended perovskite type composite oxide. Among the doping elements added to convert the complex oxide into a semiconductor or to shift its Curie point to the high temperature side or the low temperature side, typical ones of the lanthanum series elements are La, Ce, Pr, Nd,
Examples thereof include, but are not limited to, Sm. The doping elements may be used alone or in combination of two or more.

Further, typical examples of the tetravalent metal element constituting the B site include Ti, Zr and Sn, and these may be used alone or in combination of two or more kinds. As the alkoxide of these tetravalent metal elements, any one can be used, but an alkoxy group having 15 or less, preferably 8 or less carbon atoms is desirable. Representative examples of titanium alkoxides are titanium isobutoxide (Ti (OC ₄ H ₉ ) ₄ ), titanium isopropoxide (Ti (OC ₃ H ₇ ) ₄ ), dibutoxyditriethanol-aminate. Titanium, dibutoxy
(2- (hydroxyethylamino) ethoxy) titanium (Ti (C
₄ H ₉ O) _2. (N (C ₂ H ₄ OH) ₂ (C ₂ H ₄ O)) ₂ ) and the like, but are not limited thereto.

As the alkali, the general formula: MOH
(However, M represents an alkali metal or ammonium group)
Hydroxide represented by, specifically, NaOH, KOH,
There are LiOH and NH ₄ OH, which can be used alone or in combination of two or more kinds.

In the process of manufacturing the perovskite type complex oxide, the pH is 12 or more throughout the whole process from the step of forming the basic composition represented by the general formula: ABO ₃ to the step of forming the compound of the doping element. Preferably, it is carried out under conditions of 14 or more and a temperature of 60 to 95 ° C. Also, roasting is usually 10
It is performed at a temperature of 00 ° C. or lower.

[0011]

When an alkoxide of a tetravalent metal element is added to a warm aqueous solution of at least one alkaline earth metal hydroxide under alkali, a general formula: ABO ₃ , (wherein , A represents at least one alkaline earth metal, and B represents at least one tetravalent metal element.) The basic composition of the perovskite-type composite oxide represented by the formula (3) is formed and precipitated, and the reaction solution is further alkoxide of a doping element. Is added, the compound is hydrolyzed and a compound of the doping element, for example, Ce (OH) ₃ is produced and precipitated in a state of being uniformly dispersed in the precipitate of the basic composition. When this mixed precipitate is heat-treated, the semiconducting agent and / or Curie point shift agent dissolves only in the A site, so that a perovskite type complex oxide powder having a desired composition is produced.

An embodiment of the present invention will be described below.

[0013]

Example: Barium hydroxide 0.3 in 3 liters of boiling water
After dissolving 34 mol and 1.05 mol of sodium hydroxide, while stirring the solution, titanium isopropoxide was added.
An alkoxide solution prepared by diluting 0.35 mol of (Ti (OC ₃ H ₇ ) ₄ ) with 150 ml of isopropyl alcohol is added to form and precipitate barium titanate and excess titanium amorphous titanium oxide, and the reaction solution is heated to 90 to 95 ° C. Aging for 3 hours while maintaining During aging, boiling water is occasionally replenished to keep the amount of the reaction solution constant.

After completion of aging, an alkoxide solution prepared by diluting 0.0157 mol of cerium isopropoxide with 50 ml of isopropyl alcohol at the above temperature was added to form and precipitate a cerium compound (Ce (OH) ₃ ), and then the reaction solution. Aging for 1 hour. During the entire reaction and aging steps, nitrogen gas is constantly blown into the reaction vessel to prevent carbon dioxide gas in the air from being dissolved and dissolved in the reaction solution. The precipitate is filtered off and the filtrate pH is 9.5-10.
It is repeatedly washed with pure water to remove Na ions, and the washed precipitate is dispersed in pure water to prepare a slurry, which is dried by a spray drying method, and the dried powder is dried in air at 900 ° C. To obtain a barium titanate-based dielectric ceramic powder.

The result of X-ray diffraction analysis of the obtained powder is shown in FIG. From FIG. 1, it is understood that the produced powder is a single phase of (Ba _0.955 Ce _0.045 ) TiO ₃ in which Ce is completely dissolved. Further, when the powder was observed with a transmission electron microscope, the particle size was very fine as 0.1 to 0.2 μm.

[0016]

[Comparative Example] In order to obtain a perovskite-type composite oxide powder having a composition of (Ba _0.955 Ce _0.045 ) TiO ₃ , 188.5 g of barium carbonate, 79.9 g of titanium oxide, and 7.55 g of cerium oxide were sufficiently mixed and ground by a ball mill. Then, the mixed powder is roasted at 1300 ° C. and then pulverized by a ball mill for 16 hours to obtain a dielectric powder.

The result of X-ray diffraction analysis of the obtained powder is shown in FIG. From this figure, the produced powder is (Ba _0.955 Ce
_0.045 ) It is understood that TiO ₂ , CeO and other oxides are contained instead of the single phase of TiO ₃ . The particle size is 0.
It was 5 to 1.5 μm. From this, it is understood that the particle size distribution width is wide.

[0018]

As is apparent from the above description, according to the present invention, a perovskite-type composite oxide having a basic composition is formed in advance by a solution reaction, and a semiconducting agent and / or Curie point shift is generated in the reaction solution. A solution containing a doping element serving as an agent was added to precipitate a compound of the doping element together with the perovskite-type composite oxide, and the formed mixed precipitate was roasted, so that the desired doping element was dissolved. A single-phase perovskite-type composite oxide powder can be obtained, and furthermore, it can be roasted at a low temperature of around 900 ° C. Moreover, the obtained powder has a fine particle size of about 0.1 to 0.2 μm, and it is possible to obtain a powder having high surface activity, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a view showing an X-ray diffraction pattern of a perovskite type complex oxide produced by the method of the present invention.

FIG. 2 is a view showing an X-ray diffraction pattern of a perovskite type complex oxide manufactured by a conventional method.

Claims (1)

[Claims] 1. The general formula: (A _1-x A ′ _x ) BO ₃ , (wherein A
Is at least one alkaline earth metal, A ′ is at least one doping element selected from the group consisting of bismuth and lanthanum series elements, B is at least one tetravalent metal element, and x <0.1. In the method for producing a perovskite-type composite oxide powder represented by the formula (4), 4 parts are added to a warm aqueous solution in which at least one hydroxide of an alkaline earth metal and 1 to 4 mol of alkali corresponding to the hydroxide are dissolved. Addition of alkoxide of valent metal element General formula: AB
O ₃ , (wherein A is at least one alkaline earth metal,
B represents at least one tetravalent metal element. ), The perovskite-type composite oxide, characterized in that after the basic composition shown in (1) is formed and precipitated, an alkoxide of a doping element is added to form and precipitate a doping element compound, and the obtained mixed precipitate is roasted. Powder manufacturing method.