JPH01111724A - Production of barium titanate - Google Patents

Abstract

PURPOSE:To obtain the above substance of formula Ba2Ti9O20, by substituting Zr alkoxide in a specified amt. for Ti alkoxide and by calcining in air at a low temp. in producing barium titanate from Ba compd. selected among barium acetate, Ba(OH)2 and Ba alkoxide, and Ti alkoxide by hydrolyzing, drying and calcining. CONSTITUTION:One or more kinds of Ba compd. selected among barium acetate, Ba(OH)2 and Ba alkoxide, Ti alkoxide and 1-10mol.% Zr alkoxide, basing on the amt. of Ti alkoxide, are used by the total amt. of Ti and Zr and the amt. of Ba compd. equiv. to Ba2Ti9O20, respectively, mixed with ethylene glycol monomethyl ether or the mixed solvent of >=10vol.% ethylene glycol monomethyl ether and alcohol, hydrolyzed in the presence of water in the amt. of 0.001-4 times mol., base on the total mol. of Ti and Zr, to gelatinize, dried and thereafter, calcined at 800-1,000 deg.C in air to obtain the expected substance.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for producing barium titanate, and more particularly to a method for producing barium titanate in which the firing humidity can be lowered.

Technical background of the invention and its problems Conventionally, as a method for producing barium titanate, a method has been known in which titanium oxide and barium oxide are mixed and then the mixture is heated and sintered to cause an in-phase reaction. It was getting worse. These conventional methods generally require firing temperatures as high as 1300'C.

By the way, J of American Ceramic
5ociety Volume 41, Volume 10 @, Volumes 390-39
Page 4 discloses a BaO-TiO2 system stabilized with ZrO2;
OT! Even in the 02 series, the firing temperature reaches as high as 1150'C, and the firing temperature has not been sufficiently lowered.

In addition, the present inventors have disclosed in Japanese Patent Application No. 163975/1983 that titanium alkoxide and lower carboxylic acid barium salt are uniformly mixed in a solvent containing ethylene glycol monomethyl ether, and the mixture is gelled by hydrolysis to form a rough texture. We proposed a method for producing barium titanate, which is characterized by calcination.

According to this method, a barium compound that is inexpensive and easy to handle can be used as a raw material, and barium titanate with a small shrinkage rate and less possibility of cracking can be obtained. If you try to do this, it will require quite a high temperature even if the firing is done in an oxygen atmosphere.
Therefore, when forming a thin film of barium titanate on the surface of a substrate or electrode, it is necessary to select a substrate or electrode material that can withstand high temperatures.

The inventors of the present invention conducted intensive research to solve the above-mentioned problems, and found that by replacing titanium with a small amount of zirconium in the barium titanate crystal phase, 1000'
Ba 2 T by calcination in air at a low temperature of about C.
! The present invention was completed by discovering that the crystal phase of barium titanate represented by g 020 is 1q.

OBJECT OF THE INVENTION The present invention attempts to solve the problems associated with the prior art as described above, by firing in air at a temperature lower than that required by the prior art. It is an object of the present invention to provide a method for producing barium titanate, which can produce barium titanate represented by BaTi902o.

The method for producing barium titanate according to the present invention comprises at least one barium compound selected from the group consisting of barium acetate, barium hydroxide, and barium alkoxide, a titanium alkoxide, and one of the titanium alkoxides. ~10% by mole of zirconium alkoxide is uniformly mixed with ethylene glycol monomethyl ether or a mixed solvent of ethylene glycol monomethyl ether and alcohol containing 10% by volume or more of ethylene glycol monomethyl ether, and hydrolysis is performed. It is characterized in that it is gelatinized, then dried and fired.

The method for producing barium titanate according to the present invention comprises at least one barium compound selected from the group consisting of barium acetate, barium hydroxide, and barium alkoxide, a titanium alkoxide, and a 1 to 10 mol% base of the titanium alkoxide. of zirconium alkoxide is uniformly mixed with ethylene glycol monomethyl ether or a mixed solvent of ethylene glycol monomethyl ether and alcohol containing 10% or more by volume of ethylene glycol monomethyl needles, and the mixture is hydrolyzed to form a gel. Since it is then dried and calcined, barium titanate having a crystalline phase represented by B" 2 T' 9020 is obtained by firing at a temperature lower than that required by the prior art and in air. be able to.

Therefore, when forming a thin film of barium titanate on the surface of a substrate, electrode, etc., the heat resistance temperature required for the substrate, electrode material, etc. may be low, and as a result, a thin film can be formed on a wide range of substrates, electrode materials, etc. The effect is that barium titanate can be formed.

DETAILED DESCRIPTION OF THE INVENTION The method for producing barium titanate according to the present invention will be specifically described below.

Reaction Raw Materials In the present invention, barium acetate, barium hydroxide, or barium alkoxide is used alone or in combination as a barium source.

Specifically, barium alkoxide includes barium methoxide, barium ethoxide, barium n-propoxide, barium isopropoxide, and the like.

Among these, barium isopropoxide is preferred.

Furthermore, titanium alkoxide is used as a titanium source. Specifically, such titanium alkoxides include titanium methoxide, titanium ethoxide, titanium n-
Propoxide, titanium isopropoxide, titanium butoxide, etc. are used, and among these, titanium isopropoxide is preferred.

Zirconium alkoxide is used as the zirconium source.

Specific examples of such zirconium alkoxide include zirconium methoxide, zirconium ethoxide, zirconium n-propoxide, zirconium isopropoxide, and zirconium butoxide. Propoxide is preferred.

In the present invention, in order to hydrolyze the above alkoxides, it is necessary to coexist water in the reaction system.

As described below, this water may be water added to the reaction system, or may be moisture in the air depending on the case.

Paris, rum compounds, titanium alkoxides, as mentioned above,
Each of the zirconium alkoxides is used in the following amounts. That is, the barium compound is used in a proportion that corresponds to the composition of the target barium titanate. Further, titanium alkoxide and zirconium alkoxide are used in such an amount that the total amount of titanium and zirconium corresponds to the composition of barium titanate, and that 1 to 10% of titanium alkoxide is replaced with zirconium alkoxide. .

If the amount of zirconium alkoxide exceeds 10 mol % of the amount of titanium alkoxide, it is undesirable because the original properties of barium titanium will be lost, while if it is less than 1%, 3a 2 T! Barium titanate having the crystal phase shown by 9020 must be fired at a high temperature to prepare it (7), which is not preferred.

Solvent In the present invention, the reaction of each component as described above is carried out using an ethylene glycol monomethyl ether solvent or a mixed solvent of ethylene glycol monomethyl ether and alcohol containing 10% by volume or more of ethylene glycol-thumedel needles.

Alcohols used at this time include methanol, ethanol, n-propanol, isopropanol, n-propanol,
Butanol, 5ec-butanol, t-butanol, etc. are used. Of these, methanol or ethanol is preferred.

Reaction method At least one barium compound selected from barium acetate, barium hydroxide, or barium alkoxide,
Titanium alkoxide and tin alkoxide are uniformly mixed in ethylene glycol monomethyl ether or a mixed solvent of ethylene glycol monomethyl ether and alcohol containing 10% by volume or more of ethylene glycol monomethyl ether, and then the resulting mixture is hydrated. Decompose and gel.

Hydrolysis of the mixture as described above can be carried out, for example, by refluxing the mixture while heating with JrO to mix it uniformly, and then adding water to the system.

The water required for hydrolysis may be water added to the reaction system as described above, or may be water that has absorbed moisture in the air.

Such water is preferably used in an amount of 0.001 to 4 times the total number of moles of S1 of titanium and zirconium, preferably 0.01 to . It is desirable that the weight is 4 times the weight, particularly preferably 1 to 2 times the weight.

If the amount of water added is less than 4 times the molar amount of the total amount of titanium and zirconium, a sol suitable for dipping can be obtained, but if it exceeds 4 times the molar amount, it will easily change into a gel. Undesirable.

The gel thus obtained is then dried and calcined. Drying is usually carried out by maintaining the jqed gel at 25-70'C.

The gel dried in this way was ao o in the air.
For example, Ba 2 T! A barium titanate crystal having a crystalline phase of g 020 is obtained.

This calcination may be carried out under oxygen conditions, but it can also be carried out in air. In the present invention, even if the gel as described above is fired in air, the firing temperature at that time is 1100℃.
It can be carried out at a temperature of 1000°C or lower, preferably 1000°C or lower. In addition, in the conventional manufacturing method of barium titanate, a firing temperature of 1150'C or higher is required even when firing in oxygen.

For example, barium titanate obtained in this way is
Despite containing a small amount of zirconium, B a
2 T j , a crystalline phase represented by 020, etc.,
It has properties of barium titanate.

The barium titanate according to the present invention may be in the form of a powder or a thin film.

Effects of the Invention In the method for producing barium titanate according to the present invention, at least one barium compound selected from the group consisting of barium acetate, barium hydroxide, and barium alkoxide, titanium alkoxide, and 1 to 10 of titanium alkoxides. Mol% mother zirconium alkoxide and
Ethylene glycol monomethyl ether or a mixed solvent of ethylene glycol monomethyl ether and alcohol containing 10% by volume or more of ethylene glycol monomethyl ether is uniformly mixed, hydrolyzed to form a gel, and then dried and fired. Therefore, barium titanate having a crystal phase represented by Ba2T' 9020 can be obtained by firing in air at a temperature lower than that required by the prior art.

Therefore, when forming a thin film of barium titanate on the surface of a substrate, electrode, etc., the heat resistance temperature required for the substrate, electrode material, etc. is low. It is also excellent in that barium can be formed.

EXAMPLES The present invention will be explained below with reference to examples, but the present invention is not limited to these examples.

Example 1 Barium acetate 5.68g, titanium isopropoxide 27g
．． oog, 1.649 ml of zirconium n-propoxide were weighed and added to 150 ml of solvent to obtain a mixed solution. Each digit of barium, titanium, and zirconium is barium acetate 18.2 mol%, titanium isopropoxide 77.7
mol %, corresponding to 4.1 mol % of zirconium n-propoxide. A 10:90 mixture of ethylene glycol and ethanol was used as the solvent.

The mixture obtained in this way is heated in an oil bath,
A homogeneous solution [I] was prepared by refluxing.

Next, 3.69 parts of water, which is twice the amount of the total amount of titanium and zirconium contained in the solution [I], was weighed, and the above mixture of ethylene glycol and ethanol was added to the 3.69 parts of water. 50 d of was added in advance to solution [I] and hydrolyzed to obtain a gelled product.

The obtained white gel powder was calcined at 1000'C for 12 hours under air flow of 1 g per minute of drying wheat to obtain a crystalline powder.

When the obtained crystal powder was measured by X-ray diffraction, B
A crystal structure of a2Ti902o phase was observed.

Agent: Patent Attorney: Shunbetsu Suzuki

Claims (1)

[Claims] (1) At least one barium compound selected from the group consisting of barium acetate, barium hydroxide, and barium alkoxide, titanium alkoxide, and zirconium alkoxide in an amount of 1 to 10 mol% of the titanium alkoxide, and ethylene glycol monomethyl ether,
Or titanic acid, which is characterized in that it is uniformly mixed in a mixed solvent of ethylene glycol monomethyl ether and alcohol containing ethylene glycol monomethyl ether in an amount of 10% by volume or more, hydrolyzed to form a gel, and then dried and calcined. Method of manufacturing barium.