JPS6186423A - Preparation of compound bismuth oxide - Google Patents

Abstract

PURPOSE:To obtain fine particles of compound bismuth oxide having uniform compsn. and high purity by allowing >= two kinds of alkoxide cong. Bi alkoxide to react with each other and hydrolyzing the reaction product and calcining the hydrolyzed product thereafter. CONSTITUTION:Bi alkoxide is mixed with at least one kind of alkoxide of Ba, Sr, Ca, Pb and/or Mo, W, Nb, Ta, Ti, etc. in an org. solvent (e.g. benzene) at 0-100 deg.C to cause reaction. Decarboxylated distilled water is added to the soln. of the reaction product at 0-100 deg.C, or steam is blown out of a pressurized vessel at 100-200 deg.C to contact with the reaction product and to hydrolyze the reaction product, to obtn. powdery white precipitate. Then, the precipitate is filtered and dried, and calcined then at >=600 deg.C and < an initiating temp. of decomposition of the compound oxide. Thus, a compound Bi oxide having high purity contg. <=0.1wt% impurity and 0.01-0.1 micron particle size being expressed by the formula (where A is Ba, Sr, Ca, Pb; B is Mo, W, when n=1; Nb, Ta, when n=2; Nb, Ti, etc. when n=3).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing bismuth double oxide, which is a layered compound, by a hydrolysis reaction of an alkoxide. More specifically, the present invention relates to a method for producing bismuth double oxide, which is a ferroelectric material suitable for electronic materials.

[Prior Art] Conventionally, bismuth double oxide has been manufactured by mixing oxides of each component element and repeatedly performing a calcining and pulverizing process.

[Problems to be solved by the invention] In recent years, electronic components have been required to be smaller and have more advanced characteristics, and therefore the raw material powder used for them has also become smaller.
More than ever before, it has become necessary to have uniform composition and highly purified fine particles.

However, according to the conventional method, the obtained bismuth double oxide tends to have a non-uniform composition when observed microscopically because the oxides of each component element do not always distribute or react uniformly. It was difficult to stabilize the characteristics. In addition, there is a problem in that impurities are easily mixed in from the crushing device during crushing, resulting in deterioration of the properties as a dielectric material.

An object of the present invention is to provide a method for producing fine particles of bismuth double oxide with uniform composition and high purity.

[Means for Solving the Problems] The present invention involves mixing and reacting two or more alkoxides containing at least bismuth alkoxide, hydrolyzing the reaction product, and then calcining the hydrolysis product. This is a method to obtain bismuth double oxide.

The bismuth double oxide is (Bi2(h)""(A n-
IBn 03 n-+ F (However, A is Ba, Sr, C
a or Pb, B is Mo or W when n=1, Nb or Ta when n=2, Nb or Ti when n=3, n
= 4.5 or 8, Ti) c7) structure can be taken.

As used herein, "alkoxide" refers to a compound in which the hydrogen element of the OH group of alcohol is replaced with a metal element.

The starting materials of the present invention are two or more alkoxides including bismuth alkoxide, and the alkoxides other than bismuth alkoxide include barium alkoxide, strontium alkoxide, calcium alkoxide, lead alkoxide, molybdenum alkoxide, tungsten alkoxide, niobium alkoxide, and tantalum alkoxide. , titanium alkoxide. In the present invention, in addition to bismuth alkoxide, two or three alkoxides, which are a combination of one or two alkoxides selected from the above alkoxides, are used as starting materials.

The component alkoxides of each of the above two or three combinations are mixed to a desired composition and reacted. In this case, the mixing and reaction are preferably carried out in an organic solvent. This is for the purpose of facilitating mixing, promoting the reaction, and making the composition of the precipitate produced by hydrolysis, which will be described later, match the composition of the mixture. As this organic solvent, benzene, alcohol, toluene, xylene, etc. are suitable, but benzene is most suitable because of its high solubility. There is no problem as long as the reaction temperature is lower than the temperature at which each component alkoxide decomposes, but for convenience of handling, the reaction temperature is 0 to 100°C, particularly preferably 40 to 100°C.

Hydrolysis of the reaction product produced by two-leg mixing and reaction can be carried out by directly adding decarboxylated distilled water into the reaction solution. This can also be done by contacting the The reaction temperature for this hydrolysis is such that no pressure is applied! For E, each component alkoxide does not decompose and is easy to handle in the range of 0 to 100°C, particularly preferably at a temperature of 25°C.
~100°C. In the case of applying pressure or contacting with a steam stream, a temperature of 100 to 200°C is appropriate.

This hydrolysis produces a powdery white precipitate. This precipitate is separated from the hydrolyzed solution by centrifugation or filtration, and if necessary, drying such as vacuum drying is performed to obtain a powder.

4-2 Examine the physical properties and structure of the powder obtained by the reaction by X-ray diffraction, thermal analysis, and electron microscopy. Although the hydrolysis product as it is is often an amorphous bismuth double oxide, a crystalline bismuth double oxide can be easily obtained by calcination. The calcination temperature is preferably 600°C or higher and lower than the decomposition start temperature of the bismuth double oxide in order to improve the efficiency of the transition to the crystalline state, but it can also be obtained at a lower temperature or by vacuum heating. be able to.

In particular, the starting materials are bismuth alkoxide and divalent metal Ba.
, Sr 2 , Ca 2 , and Pb alkoxides, a bismuth double oxide having the following structural formula can be obtained.

(BizOz)” (An+tBnOin++))・-
--------(1) (However, A is Ba, Sr, Ca or Pb, B is Mo or W when n=1 (7), Nb or Ta when n=2, Nb when n=3 or Ti, n
= 4.5 or 8, there is Tate. ) As a result of chemical analysis, the bismuth double oxide obtained by calcination showed no impurities.
It is a substance with a high purity of 1% or less, and according to electron microscope observation, it is a fine particle with a particle size of 0.01 to 111 Lm.Also, the composition ratio of each component of metal atoms is extremely close to the stoichiometric ratio. I can confirm that there is.

[Effects of the Invention] As described above, according to the present invention, high purity, fine-grained bismuth double oxide can be produced with an atomic ratio extremely close to the target, without the conventional pulverization process, and with low energy consumption. , it has the excellent effect of being able to be manufactured uniformly.

[Examples] Next, in order to show specific embodiments of the present invention, the present invention will be explained in more detail using Examples, but the examples shown below are merely examples, and the technical scope of the present invention is limited thereby. It's not a thing.

<Example 1> 6.8 g of high-purity metallic sodium was taken, added to 100 g of dehydrated ethanol, reacted to synthesize sodium ethoxide, and anhydrous bismuth chloride BiCIx
Bismuth ethoxide Bi (OEth) was obtained by adding 31.5 g of the mixture and heating under reflux at about 80° C. for 2 hours.

The obtained bismuth ethoxide and commercially available titanium isopropoxide Ti(OPr')4 were mixed in an atomic ratio of Bi/Ti.
= 8/1.4/3.1/2 and reacted under reflux at about 80°C for 1 hour. Next, 50 Il of distilled water was decarboxylated while refluxing! When 1 was added dropwise little by little and hydrolyzed, a white powdery precipitate was formed in each reaction system. The precipitates were separated from the hydrolyzed solution by filtration, and then dried at 70° C. for 20 hours to obtain three types of powder.

The properties of the three types of powders obtained were examined by X-ray diffraction, differential thermal analysis, and thermogravimetric analysis. Furthermore, these powders were calcined at temperatures of 400°C, 600°C, 800°C, and 1000°C, respectively, and their structures were investigated by X-ray diffraction. Table 1 shows the results of X-ray diffraction analysis.

(Hereinafter, the margin of this page) Table 1 The three types of powders shown in Table 1 are all hydrolysis products and are amorphous when calcined at 400°C or lower, and monolithic when calcined at 600°C or higher. It was confirmed that a crystalline target material could be obtained.

The obtained powder was also subjected to particle size observation and composition analysis using an analytical electron microscope. As a result, the particle size of the hydrolyzed product of each powder was several tens of particles, and the particle size after calcination at 800° C. was 1000 particles (0.1 l). In addition, the composition analysis results showed that the composition of each particle was in good agreement with the batch composition.

<Example 2> Ba occupies the position "A" in the crystal lattice of the bismuth double oxide represented by the above-mentioned structural formula (1).

The alkoxides of the elements Sr and Pb, the alkoxides of the elements Ti and Nb occupying the rBJ position, and the three alkoxides of bismuth ethoxide obtained in Example 1 were prepared in an atomic ratio of ■Ba/Bi/ Ti=1/4/4■
Sr/Old/Ti=2/415 ■Bi/Nb/Ti=3/1/1■
Sr/Nb/Bi = 1/2/2■P
When mixed so that b/Nb/Bi = 1/2/2 and subjected to reflux reaction and hydrolysis in the same manner as in Example 1, a white precipitate similar to that in Example 1 was found in both reaction systems. was generated. This precipitate was separated from the hydrolyzate and dried in the same manner as in Example 1 to obtain five types of powder. The five types of powder obtained were measured in the same manner as in Example 1, and the results are shown in Table 2.

Table 2 This powder was subjected to particle size observation and composition analysis using an analytical electron microscope in the same manner as in Example 1. As a result, all powders were found to be fine particles with a uniform composition that closely matched the batch composition.

Patent applicant: Mitsubishi Mining and Cement Co., Ltd. Patent attorney, Su 1) Masayoshi (2 others), Kantenri Yu♀ Ichimasho (spontaneous) October 27, 1980 Commissioner of the Patent Office Manabu Shiga ■, 2 Indication of 1982 Patent Application No. 207171 2 Title of invention Method for producing bismuth double oxide 3 Person making amendment = Relationship with IN case Patent applicant address 5 Marunouchi-chome, Chiyoda-ku, Tokyo No. 1 Name Mitsubishi Mining Cement Co., Ltd. Representative Hisaaki Kobayashi 4, Agent 6, No increase in invention due to amendment 8,! I
Contents of the i-stop (1) On page 7, line 4 of the specification, ``According to the inventor'' is corrected to ``According to the invention.''

(2) Table 2 (3) on page 11 of the specification (3) From line 4 on page 7 to line 3 on page 3 of the specification, ``any powder'' is corrected to ``any powder.''

Claims (1)

[Claims] 1) A mixing reaction step of mixing and reacting two or more alkoxides including at least bismuth alkoxide, a hydrolysis step of hydrolyzing this reaction product, and calcination of this hydrolysis product. A method for producing bismuth double oxide, comprising: a calcination step to obtain bismuth double oxide. 2) Bismuth double oxide is (Bi_2O_2)^2^+(A_n_+_1B_nO
_3_n_+_1)^2^-(However, A is Ba, Sr,
Ca or Pb, B is Mo or W when n=1, Nb or Ta when n=2, Nb or Ti when n=3, n=4
, 5 or 8, the method for producing a bismuth composite oxide according to claim 1, having a structure of Ti).