JPH0617262B2 - Method for manufacturing zirconia sheet sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is expected to have many application fields not only for functional ceramics such as solid electrolytes and sensors, but also for structural ceramics such as heat insulating materials and refractory materials. The present invention relates to a method for producing a zirconia sheet sintered body, and more particularly to a method for producing a zirconia sheet sintered body from zirconium alkoxide.

[Conventional technology]

As described above, various methods have been proposed for producing a zirconia sheet sintered body having a wide range of applications, but in typical production methods that have been conventionally performed, zirconia prepared by various methods is used. An organic binder, a plasticizer, etc. are added to the fine powder to make a slurry-like substance, and this slurry is processed into a sheet-like formed body by various forming methods such as the doctor blade method, and sintered at a high temperature to zirconia sheet baking. I was getting a union.

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional method, the zirconia fine powder used as a raw material has a smaller particle size, so that the quality of the obtained zirconia sheet sintered body is improved. It has to be repeated, requires a great amount of pulverization power, and is difficult to obtain a high-purity fine powder due to the inclusion of foreign matter due to abrasion of a ball mill or the like during pulverization. Further, there is a drawback that it is difficult to make the manufacturing process completely continuous, and it is difficult to automate and continuous the process.

The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide a method for producing a uniform ultra-high-purity zirconia sheet sintered body which is easy to automate and continuous.

[Means for Solving the Problems]

As a result of repeated studies on a method for producing a zirconia sheet sintered body, the present invention adds β-diketone to a solution of zirconium alkoxide or an organic solvent thereof in an amount of 0.5 mol times or more and 4 mol times or less with respect to the amount of zirconium alkoxide. After reacting, the amount of zirconium alkoxide is added in an amount of 0.5 to 10 times by mole of water to hydrolyze, a viscous sol is synthesized, and an organic binder is added to the viscous sol to form a sheet. The method for producing a zirconia sheet sintered body, which is characterized by firing a green sheet by slowly drying it in an atmosphere in which vapor of an organic solvent is introduced, is effective in eliminating the above-mentioned drawbacks. It was found that they existed and succeeded in developing the present invention.

Examples of the zirconium alkoxide used in the present invention include zirconium methoxide, zirconium ethoxide, zirconium isopropoxide, zirconium normal propoxide, zirconium normal butoxide and the like. Some of the above alkoxides are solid at room temperature and some are liquid at room temperature, but it is desirable to dissolve the solid alkoxide in an organic solvent before use as a solution. As an organic solvent for dissolving the zirconium alkoxide, an alcohol such as methyl alcohol or ethyl alcohol,
Benzene, toluene, xylene, etc., or a mixture thereof can be used.

Zirconium alkoxide has a high hydrolysis rate, and when water is added, a white precipitate is easily formed or a gel is formed. Then, by adding and reacting β-diketone, the zirconium alkoxide is stabilized, the hydrolysis rate is slowed, and even if water is added, white precipitate does not occur and a viscous sol is formed. However, when the amount of β-diketone is small, a white precipitate is formed, and when it is too large, it is not hydrolyzed and does not become a viscous sol even after a long time. Therefore, the amount of β-diketone used in the reaction is preferably 0.5 mol times or more and 4 mol times or less with respect to the zirconium alkoxide, and is preferably 2 mol times. Also, the amount of β-diketone and the amount of water in hydrolysis are closely related.

As the β-diketone, acetylacetone, methyl acetoacetate, ethyl acetoacetate, malonic acid diester and the like can be used. The reaction of zirconium alkoxide and β-diketone can be carried out at room temperature, and both can be mixed and stirred at room temperature for 1 hour or more.

Water is added to the zirconium alkoxide stabilized by the reaction as described above to carry out hydrolysis to form a viscous sol. In order to generate a viscous sol, the amount of water added is 0.5 mol times or more 10 times the amount of zirconium alkoxide.
A molar ratio of less than or equal to is suitable, but the amount of β-diketone used is 2
When the amount is molar, water is preferably 5 times. The viscous sol produced at that time preferably has a viscosity of 5 poise or more. It has been found that when the viscosity is 5 poises or more, a small amount of the organic binder to be added in order to prevent cracking may be required when forming the sheet. Therefore, in order to generate a viscous sol whose viscosity is 5 poise or more, β-
Adjust the amount of diketone and the amount of water added during hydrolysis.

An organic binder is added to the above-mentioned viscous sol, and the mixture is thoroughly mixed before sheet formation. The amount of organic binder added is
Zirconia made from zirconium alkoxide (Z
30 wt% or less relative to rO ₂ ) is suitable, but 5 to 10 wt% is desirable. The type of organic binder is preferably soluble in an organic solvent, and one or two kinds of organic binders of polyvinyl butyral (PVB) and hydroxypropyl cellulose (HPC) are particularly desirable from the viewpoint of forming a sheet. Polyethylene, polyvinyl alcohol,
Polyvinyl chloride or the like is used. Methyl agitate,
It is also possible to add a plasticizer of dibutyl phthalate.

As the sheet forming method, various forming methods conventionally used for sheet forming can be applied, but the doctor blade method is suitable because it can be mass-produced.

Drying after forming the sheet is at room temperature and in air,
It may crack and yield is poor. Therefore, by gently drying the molded product in the atmosphere in which the vapor of the organic solvent is introduced, a green sheet without cracks can be obtained. As the vapor of the organic solvent, alcohol vapor is preferable.

The green sheet thus obtained is cut into a desired size and fired at a temperature of about 1200 to 1800 ° C. By this firing, a zirconia sheet sintered body without cracks can be obtained. The thickness of the sintered body may be about 10 to 250 μm.

In addition, when manufacturing a conventional zirconia sintered body, in order to suppress the phase transition between a monoclinic crystal and a tetragonal crystal accompanied by a significant volume change, a certain amount of a stabilizing material such as yttria, calcia, magnesia, etc. is added to zirconia. It is well known that the addition of yttrium, calcium, or magnesium (for example, YCl ₃ .6H ₂ O) in the reaction raw material before synthesizing the viscous sol in order to obtain this effect in the present invention.
It is possible to add materials such as.

[Action]

When an attempt is made to obtain a zirconia product using zirconium alkoxide, the zirconium alkoxide has a high hydrolysis rate, so that a white precipitate or gel is easily formed when water is added. According to the present invention, when β-diketone is added to zirconium alkoxide and reacted, the zirconium alkoxide is stabilized, the hydrolysis rate is slowed, white precipitate is not formed even when water is added, and it is in a viscous sol state. can get. This viscous sol is very convenient for forming a sheet. Then, a green sheet without cracks can be obtained by slowly drying the sheet-formed molded article in the atmosphere in which the vapor of the organic solvent is introduced. When this green sheet is fired, an integrated and dense sheet sintered body is obtained.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1 0.01 mol of zirconium isopropoxide was dissolved in 100 ml of ethal, 0.02 mol of acetylacetone was added, and the mixture was stirred at room temperature for 2 hours. After that, 0.05 mol of water was added slowly with a dropping funnel over about 20 minutes.
The mixture was refluxed at a temperature of 80 ° C. for 1 day to obtain a viscous sol having a viscosity of 10 poise. Polyvinyl butyral was added to the obtained viscous sol.
0.123 g of (PVB) was added, and the mixture was stirred at room temperature for 1 day. As a result, a viscous sol-organic binder mixed viscous product having a viscosity of 25 poise was obtained. This mixed viscous material was tape-cast by the doctor blade method and gently dried for 4 days in a dryer introducing ethanol vapor to obtain a green sheet. This was baked at 1500 ° C. for 2 hours to obtain a zirconia sheet sintered body. The thickness was 98 μm. The X-ray analysis result of this sintered body showed peaks of monoclinic and tetragonal zirconia.

Example 2 Zirconium butoxide (commercially available 90% Vitanol solution) 11
100 g of acetylacetone was added to 1 g, and the mixture was stirred at room temperature for 2 hours. After adding 3.75 g of water with a dropping funnel, 17.53 g of YCl ₃ .6H ₂ O was added and refluxed at 80 ° C. for 1 day to obtain a viscous sol having a viscosity of 8 poises. To the obtained viscous sol, 2.56 g of hydroxypropyl cellulose (HPC) and 3.6 g of glycerin were added, and ultrasonic waves were applied for 1 hour, and then 1
When the mixture was agitated for a day and thoroughly mixed, a viscous sol-organic binder mixed viscous product having a viscosity of 20 poise was obtained. This mixed viscous material is tape cast by the doctor blade method,
It was slowly dried for one week in a drier in which ethanol vapor was introduced to obtain a green sheet. This is 1500 ℃, 2
Firing was carried out for a period of time to obtain a zirconia sheet sintered body.
Its thickness was 80 μm. The result of X-ray analysis of this sintered body showed a peak of cubic zirconia.

Comparative Example 1 0.01 mol of zirconium isopropoxide was dissolved in 100 ml of ethanol, and 0.05 mol of water was slowly added dropwise with a dropping funnel. A white precipitate formed, which was not suitable for sheet forming.

Comparative Example 2 A viscous sol was synthesized in the same manner as in Example 1, and the viscous sol was tape-cast by the doctor blade method and dried in air at room temperature to cause cracks in the green sheet.

Comparative Example 3 A viscous sol was synthesized in the same manner as in Example 1, 0.123 g of polyvinyl butyral (PVB) was added to this viscous sol, and the mixture was stirred at room temperature for 1 day and mixed with a viscous sol having a viscosity of 25 poise-organic binder. A viscous liquid was obtained. This was tape-cast by the doctor blade method and dried in air at room temperature. Cracks, cracks, and sledges were observed in 9 of the 20 lots.

〔The invention's effect〕

According to the present invention, it is possible to obtain a uniform ultrahigh-purity zirconia sheet sintered body without cracks. Further, in the present invention, the reproducibility is good and the management of the manufacturing process is easy, so that the manufacturing process can be completely continuous and can be automated.

Claims (2)

[Claims] 1. A solution of zirconium alkoxide or an organic solvent thereof, based on the amount of zirconium alkoxide.
After adding β-diketone in an amount of 0.5 mol times or more and 4 mol times or less and reacting it, the amount of zirconium alkoxide is 0.
Hydrolyze by adding 5 mol times to 10 mol times of water to synthesize a viscous sol, add an organic binder to the viscous sol, form a sheet, and slowly in an atmosphere in which vapor of an organic solvent is introduced. A method for producing a zirconia sheet sintered body, which comprises drying to obtain a green sheet and sintering the green sheet. 2. The organic binder is one or more of polyvinyl butyral and hydroxypropyl cellulose.
The method for producing a zirconia sheet sintered body according to claim 1, which is a seed.