JPH0717378B2 - Method for producing stabilized zirconia thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an yttria-stabilized zirconia thin film adhered to a substrate used as an electrode material, an electronic material or the like.

[Conventional technology]

As a conventional method for producing a ceramic thin film, a so-called doctor blade method, in which an oxide powder, a binder, and a dispersion medium are kneaded, formed into a flat film, and then dried and baked, is well known.

[Problems to be Solved by the Invention]

However, the film of yttria-stabilized zirconia (completely stabilized type) produced by the conventional doctor blade method is like paper by itself as a thin film, and its toughness is low, so it is brittle and difficult to support on the surface of the substrate. However, when the film thickness is increased to increase the strength, the film performance is deteriorated.

In view of the above-mentioned state of the art, the present invention does not have a problem as in the yttria-stabilized zirconia film obtained by the conventional method,
An object of the present invention is to provide a method for producing a dense and highly uniform yttria-stabilized zirconia thin film that is in close contact with a substrate.

[Means for Solving the Problems]

The present invention mixes yttria-stabilized zirconia particles having a particle size of 1 to 5 μm with two or more groups of yttria-stabilized zirconia particles having a particle size of 1 μm or less and having different diameters to form a slurry to form a slurry. It is a method for producing an yttria-stabilized zirconia thin film adhered to a substrate, which is characterized in that it is applied to the substrate and dried and baked.

In the present invention, the particle size of the raw material yttria-stabilized zirconia particles is specified from the viewpoint of the filling state and the sinterability of the raw material yttria-stabilized zirconia particles.

In general, even if the ceramics raw materials including the yttria-stabilized zirconia have the same composition, the temperature at which they start to melt differs depending on the size of the particles, and as a matter of course, the larger the melting temperature, the higher the particles. The sintering temperature of the yttria-stabilized zirconium particles having a normal particle size is 1400 to 1600 ° C., and the particle size of 1 to 5 is also used in the present invention as a standard.
μm Yttria-stabilized zirconia particles (sintering temperature 1400
〜1600 ℃), and use the particles so that they make up the majority of the raw material yttria-stabilized zirconia. Then, as the rest of the raw material, yttria-stabilized zirconia particles having a particle diameter of 1 μm or less are used. When the raw material particles having both the particle diameters are mixed and filled, a small amount of particles having a particle diameter of 1 μm or less fills a gap between a large amount of particles having a particle diameter of 1 to 5 μm. When sintered in this state, particles having a particle size of 1 μm or less melt at a lower temperature than particles having a particle size of 1 to 5 μm and behave like glue, so it is necessary to melt the entire raw material mixed particles in order to sinter them. As a result, low temperature sintering is possible as compared with the conventional method. For example, yttria-stabilized zirconia particles having a particle size of 1 to 5 μm are usually sintered at 1400 to 1600 ° C., but if ultrafine yttria-stabilized zirconia particles having a particle size of 0.01 to 0.02 μm are mixed therein, the sintering temperature is 12
It becomes 00-1300 ℃.

However, the particle size is 1 to 5 μm and the particle size is 0.01 to 0.02.
When a mixed raw material of ultra-fine particles such as μm is sintered, since there are no particles having an intermediate particle diameter, the shrinkage due to sintering is large, which causes the obtained yttria-stabilized zirconia thin film to crack.
Therefore, in the present invention, a larger particle size than the yttria-stabilized zirconia particles having a particle size of 1 μm or less, for example,
Particles with a diameter of 0.1-1 μm and smaller particles, for example 0.01-
At least two kinds of particles having a diameter of 0.05 μm having different diameters are used to prevent shrinkage during sintering. Of course, mixing three or more kinds of particles having a particle size of 1 μm or less is not hindered, but the operation becomes complicated and it cannot be said that this is a very good measure.

Among the yttria-stabilized zirconia particles having a particle size of 1 μm or less, particles having a relatively large particle size, for example, 0.1 to 1 μm, preferably particles having a diameter of 0.1 to 0.5 μm are fine particles, and particles having a relatively small particle size, for example, 0.01 to 0.05. , Preferably 0.01 to 0.02
When the particles having a diameter of μm are referred to as ultrafine particles, and the yttria-stabilized zirconia particles having a particle diameter of 1 to 5 μm are referred to as coarse particles, the mixing ratio of coarse particles: fine particles: ultrafine particles is the yttria-stabilized zirconia thin film produced. The density is determined by the particle size of each raw material particle so that the density becomes maximum, but it is difficult to determine in general.For example, coarse particles having a particle size of 1 to 5 μm have a particle size of 0.
When fine particles having a particle size of 1 to 0.5 μm and ultrafine particles having a particle size of 0.01 to 0.02 μm are mixed, coarse particles: fine particles: ultrafine particles = about 10: 3: 1 by weight ratio is preferable. Even if the yttria-stabilized zirconia particles are blended in this way, and the slurry is applied and dried, the density becomes 60 to 70%. This is because the density of a normal compacted body of yttria-stabilized zirconia particles is 50
The value is remarkably higher than that of less than%.

The yttria content of the yttria-stabilized zirconia used in the present invention is 1 to 20 mol% with respect to zirconia (ZrO ₂ ) as yttria (Y ₂ O ₃ ) (itutria is liberated at 20 mol% or more). is there. Itutria is 8
If it is less than mol%, it becomes partially stabilized zirconia, and it is 8 mol%.
The above results in completely stabilized zirconia. Since itutria is more expensive than zirconia, it should be used in the minimum necessary amount according to the purpose. Considering conductivity, about 8 mol% is optimal.

The particle size of yttria-stabilized zirconia is 1-5.
Coarse particles of μm and fine particles having a particle size of 0.1 to 0.5 μm can be used by classifying commercially available yttria-stabilized zirconia powder by an air classification method or the like. Also, 0.01
Ultrafine particles of yttria-stabilized zirconia having a particle size of about 0.02 μm can be obtained by hydrothermal treatment of a mixed aqueous solution of zirconium oxychloride and yttrium chloride under a temperature condition of about 200 ° C.

The slurry of yttria-stabilized zirconia, after mixing the yttria-stabilized zirconia of each particle size, added a binder such as polyvinyl alcohol, further dispersed using a ball mill after adding water as a dispersion medium, after dispersion treatment,
Obtained by vacuum degassing using a rotary evaporator.

〔Example〕

Commercially available 8 mol% yttria-stabilized zirconia with an average particle size of 1.5 μm was air classified to coarse particles of 1 to 5 μm and 0.1 to 0.5 μm.
The particles were classified into μm fine particles.

Zirconium oxychloride (ZrOCl ₂ · 8H ₂ O) 3.68 mol
/ l, yttrium chloride (YCl ₃ · 6H ₂ O) 0.32 mol / l The mixed solution with distilled water added was placed in a Teflon-lined stainless steel pressure-resistant container and sealed, then sealed 200
It was placed in a constant temperature bath at ℃ and kept for 5 days (120 hours). Thus, yttria-stabilized zirconia ultrafine particles having a particle size of about 150Å (0.015 μm) were obtained.

Next, the above powders were blended in such a manner that coarse particles having a polymerization ratio of 1 to 5 μm were 10.0, fine particles having a particle size of 1 to 0.5 μm was 3, and ultrafine particles having a particle diameter of 0.05 μm were 1 to give a binder. As a result, polyvinyl alcohol was added to the powder in an amount of 1 wt% and water was added to adjust the slurry concentration to 15 wt%, and the mixture was pulverized and mixed for 24 hours using a ball mill to obtain a slurry. Next, the slurry was vacuum degassed using a rotary evaporator to obtain a coating slurry.

This slurry has an average pore size of 1.5 μm, a thickness of 1 mm and a porosity of 65.
% Of the alumina-based substrate was deep-coated on the surface and then dried indoors. Next, the temperature was raised to 1250 ° C. at a rate of temperature increase of 2 ° C./min, and this temperature was maintained for 4 hours, followed by furnace cooling.

By doing so, a dense yttria-stabilized zirconia film having a thickness of about 15 μm was formed on the surface of the alumina substrate tube.

For reference, coarse particles of 1 to 5 μm, fine particles of 0.1 to 0.5 μm, and ultrafine particles of 0.015 μm, each of which is a single particle, is used to form a slurry in the same manner as described above, and then coating, drying and firing are performed under the same conditions. A comparative sample was prepared.

Gas permeation method (N ₂ ) as a method to evaluate the homogeneity of the membrane
And two methods of electrical conductivity (DC 4-terminal method) were used.

In the evaluation by the gas permeation method, a pressure difference (kg / cm ² ) was applied to both sides of the membrane, and the gas permeation coefficient was obtained from the amount of nitrogen permeating through the membrane at this time. The test results are shown in FIG. In Fig. 1, the horizontal axis is the differential pressure (kg / cm ² ) and the vertical axis is the gas permeation coefficient (N ₂ ).
Is. The figure is obtained by blending three different particle sizes of the present invention, and and are each 1 to 5 μm.
And 0.1 to 0.5 μm. When the thickness of 0.015 μm was used alone, cracking occurred and the transmittance was higher than that of 1 to 5 μm. As a result of this test, it was found that the method of the present invention is useful because the amount of gas permeation is considerably reduced.

The conductivity was evaluated by attaching a lead wire for measurement of a direct current four-terminal method to the sample and then heating it. The measurement result of the electric conductivity is shown in FIG. In FIG. 2, the horizontal axis represents the reciprocal of absolute temperature multiplied by 10,000, and the vertical axis represents the conductivity. The figures are obtained by blending three different particle sizes according to the present invention.
Those of 0.5 μm and 0.015 μm. As a result of this test, the method of the present invention has a relatively high electric conductivity, indicating that the present invention is useful. Results in insufficient sintering, and results in cracking due to sintering, resulting in a decrease in conductivity.

As described above, in the present invention, it is clear that it is possible to obtain a dense and highly uniform zirconia film.

〔The invention's effect〕

According to the present invention, it is possible to produce a dense yttria-stabilized zirconia thin film adhered to a substrate at a relatively low temperature from the viewpoint of particle filling property and use of ultrafine particles.

[Brief description of drawings]

FIG. 1 is a chart showing the relationship between the differential pressure and gas permeation coefficient of the prototype sample, and FIG. 2 is a chart showing the relationship between temperature and conductivity of the prototype sample.

Claims (1)

[Claims] 1. A slurry is formed by mixing yttria-stabilized zirconia particles having a particle size of 1 to 5 μm, and two or more groups of yttria-stabilized zirconia particles having a particle size of 1 μm or less and having different diameters with a binder. A method for producing an yttria-stabilized zirconia thin film adhered to a substrate, which comprises applying the slurry to the substrate, followed by drying and baking.