JPH0678191B2 - Method for producing zirconium titanate-based ceramics - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a low-expansion zirconium titanate-based ceramics.

This ceramic is used as a low expansion material.

[Conventional technology]

Among the raw material powders of the zirconium titanate-based ceramics, the zirconia raw material powder is extremely likely to aggregate. Even if a ceramic raw material powder is prepared by a dry method using such a zirconia raw material powder, the average particle size is 1 to 2 μm.
That is all. It is difficult to obtain a high-density and high-performance structural material ceramics even if such a raw material powder is used.

[Problems to be solved by the invention]

The present invention has been made to solve the above-mentioned drawbacks in the synthesis of the zirconium titanate-based ceramics by the dry method, and an object thereof is to prepare a modified zirconia raw material powder of submicron class having good dispersibility and use the powder. A simple method for synthesizing raw material powders of zirconium titanate ceramics with high sinterability and high bulk density, and then sintering these powders to produce high-performance and high-density low-expansion zirconium titanate ceramics. To provide.

[Means for solving problems]

As a result of earnest research to achieve the above-mentioned target, the present inventors have found that, in the process of producing low-expansion zirconium titanate ceramics, a solution containing zirconium and an appropriate amount of at least one metal component other than zirconium constituting the ceramics. When the solution is subjected to a hydrolysis reaction to generate a sol, zirconium-containing particles are less likely to agglomerate due to the non-uniformity of the system, and the sol body obtained after that is dried at 700 to 1300 ° C. It was found that when calcined, a submicron grade powder (modified zirconia powder) with extremely few agglomerates can be obtained. Using this as a raw material, the compounds of the remaining constituent parts of the desired ceramic composition are mixed by a dry method and calcined to easily obtain a raw material powder with excellent sub-micron grade powder characteristics. It was found that an extremely high density zirconium titanate-based ceramics can be easily obtained without sintering aid by sintering. The present invention has been completed based on this finding.

The gist of the present invention is a combination of the following three steps (a to c).

Step (a): A solution containing an appropriate amount of at least one metal component other than zirconium constituting zirconium titanate-based ceramics and zirconium is prepared, a hydrolysis reaction is performed to generate a sol, and the sol body is obtained. After drying 700-130
Step of calcination at 0 ° C. In this step, modified zirconia is obtained which avoids agglomeration during the formation of a coprecipitate and can also be used in the production of PZT, PLZT and the like.

Step (b): A step of mixing the calcined product obtained in step (a) with the compound of the remaining constituent metal components of the intended zirconium titanate-based ceramics composition and calcining at 500 to 1300 ° C. In this step, the desired compound composition is obtained by adding the remaining components.

Step (c): molding the calcined powder obtained in step (b)
The process of sintering at 700-1700 ℃.

Compounds for making the zirconium solution include zirconium oxychloride, zirconium oxynitrate, zirconium chloride and zirconium nitrate. As a solvent for the zirconium solution, water or alcohol that dissolves the above compound is used. All of the above compounds are soluble in water, and zirconium oxychloride and zirconium chloride are soluble in ethanol. Furthermore, in order to prepare a zirconium solution, metallic zirconium can be dissolved in aqua regia or HF and used. Compounds for preparing a solution of a metal component other than zirconium, particularly titanium compounds include Ti (NO ₃ ) ₄ , TiCl ₄ , and Ti (SO ₄ ) ₂ . Water or alcohol is used as the solvent of this solution. The zirconium solution and the solution other than zirconium may be prepared separately, or may be prepared by dissolving each compound in the same solvent.

The hydrolysis reaction is carried out under heating (around 100 ° C), and the sol is collected by filtration and washing.

Further, in the zirconium titanate-based ceramics, it is customary to add a small amount of an auxiliary agent (for example, SnO ₂ ) in order to improve the sinterability and characteristics, and these auxiliary agents are added in the step (a) or It may be added appropriately in step (b).

The amount of titanium dissolved in the zirconium-containing solution is preferably an amount that can suppress aggregation of the zirconia powder finally obtained by the addition thereof. The calcination temperature of the obtained sol body is 700 to 1300 ° C. If the temperature is lower than 700 ° C, the agglomeration remarkably occurs, and if it exceeds 1300 ° C, the particles tend to become coarse. The powder thus obtained is mixed with the deficiency of the remaining components. In this case, added TiO ₂ and SnO ₂
Use a submicron grade particle size. The calcination temperature of this mixture needs to be within the maximum temperature range above which the solid phase reaction is almost or completely completed and no remarkable particle growth occurs, and is preferably in the range of 500 to 1300 ° C.

The powder thus obtained is molded and sintered. The sintering temperature is determined in the same manner as the calcination temperature of the above mixture, but is generally in the range of 700 to 1700 ° C.

〔Example〕

43.57 ml of an aqueous titanium tetrachloride solution (0.75 mol / l) and 150 ml of zirconium oxychloride (0.873 mol / l) were mixed. By holding this aqueous solution at 100 ° C. for 100 hours, a hydrolysis reaction was performed to obtain a sol containing Ti ⁴⁺ and Zr ⁴⁺ . This was washed, dried, and then calcined at 1200 ° C. to prepare (Zr _0.8 Ti _0.2 ) O ₂ powder.

The average particle size of this powder was 0.32 μm.

The obtained powder (3.44 g), commercially available TiO ₂ fine powder (0.288 g), and SnO ₂
After mixing 2.170 g of fine powder with a ball mill all day and night, 740
It was calcined at ℃ for 1 hour to obtain ZrTi _0.4 Sn _0.6 O ₄ powder. The zirconium titanate-based ceramics produced from the powder showed an extremely high firing density. For example, this ZrTi _0.4 Sn _0.6
When O ₄ powder was molded at 1 ton / cm ² and then sintered at 1400 ° C. for 2 hours in an atmosphere of oxygen gas, the density of the obtained ceramics was 2.88, which was a value very close to the theoretical density.

〔The invention's effect〕

According to the method of the present invention, the modified zirconia powder for zirconium titanate-based ceramics can be formed into submicron particles having very few secondary particles by the first step (a), and by using this, thereafter, by a simple dry method,
Submicron grade raw material powder can be easily obtained, and an extremely high density ceramic can be obtained by using this raw material powder. In addition, the following effects can be obtained.

(1) Since the (Zr _0.8 Ti _0.2 ) O ₂ powder obtained by calcination can be sufficiently dispersed, it can be supplied as a raw material powder without requiring a pulverization step of the calcined product.

(2) Obtained by dry method from the calcined (Zr _0.8 Ti _0.2 ) O ₂ powder
The ZrTiO ₄ -based powder is also obtained in a monodisperse state, and thus has the characteristics of sufficiently easy sinterability and high bulk density even if the pulverization step is omitted.

(3) Hot-pressing or HIPing low-expansion zirconium titanate-based ceramics, which requires extremely high density
An extremely high density can be obtained by omitting operations such as (hot gas sintering) and simply performing solid-phase sintering and not necessarily requiring a sintering aid.

(4) By mass-producing the modified zirconia powder having excellent powder characteristics, a high-performance zirconium titanate-based ceramic (porcelain) can be supplied at an extremely low cost.

Claims (1)

[Claims] 1. A method of: (a) preparing a solution containing zirconium and an appropriate amount of a metal component other than zirconium constituting zirconium titanate-based ceramics, performing a hydrolysis reaction to produce a sol, and drying the sol body. Calcining at 700 to 1300 ° C, (b) mixing the calcined product with the compounds of the remaining constituent metal components of the desired ceramic composition and calcining at 500 to 1300 ° C, (c) And a step of molding the calcined powder and sintering it at 700 to 1700 ° C., a method for producing a zirconium titanate-based ceramics.