JPS60112620A - Mixed electrically-conductive zirconia and its nanufacture - Google Patents

Abstract

PURPOSE:To manufacture the titled zirconia having ion- and electron- electrical conductivities by heating a (partially) stabilized zirconia sintered body having an ion-electrical conductivity under the carbon atmosphere and diffusing the carbon to the sintered body. CONSTITUTION:The (partially) stabilized zirconia sintered body having an ion- electrical conductivity which is obtained by molding ZrO2 incorporated with >=2mol% stabilizer (e.g. MgO) to a deisred form and calcining it at >=1,500 deg.C is calcined at >=1,500 deg.C under the carbon atomsphere. Or, after 0.05-5wt% carbon powder having 0.01-0.5mum average grain size is added to ZrO2 incorporated with a stabilizer and molded to a desired form, it is calcined at >=1,500 deg.C under an inert gas atmosphere and the carbon is dispersed into the zirconia sintered body. By said method, a mixed electrically-conductive zirconia having an electron-electrical conductivity of <=10mOMEGA.cm specific resistance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to mixed conductive zirconia and methods of manufacturing the same. More specifically, the present invention relates to zirconia exhibiting ionic conductivity and electronic conductivity and a method for producing the same.

Zirconia (zirconium acetate Zr02) is a colorless crystal and is known to undergo the following phase transition.

1000'C1900℃ Monoclinic system←→tetragonal system←→cubic system When using this as a refractory, abnormal thermal expansion due to the above phase transition is undesirable, so add 3 to 5% to this. When stabilized as an equiaxed type by adding any stabilizer to the degree of Since it can withstand temperatures up to about 2300°C, it is used as a material for equipment used in physics and chemistry and the chemical industry that is used at high temperatures, as well as for heating elements and solid electrolyte materials.

So-called stabilized zirconia (cubic crystal system) or partially stabilized zirconia (tetragonal crystal threads mixed in the cubic system) that have been improved to exhibit equiaxed crystal threads over all operating temperatures.
are used as solid electrolyte materials due to the inherent ionic conductivity of zirconia, but these materials, especially partially stabilized zirconia, which generally has a high fracture toughness value, are used in cutting tools, dies, nozzles, and It is thought that it can also be used as a structural material for moving parts and the like. However, when using these structural materials, machining is not possible, so if electric discharge machining is used instead, it is possible to cut out complex 7: round-shaped structural parts, but in the case of zirconia, However, there is a problem in that electrical discharge machining cannot be performed smoothly.

In order to solve these problems, stabilized zirconia 1fc with V cracks and ionic conductivity can be made by adding electronic conductivity to partially stabilized zirconia.For example, (ZrO2)0.892''20+1)0 It is known that 047 series VC (OsO4) is added and sintered to make a mixed conductor.However, the 0e02 used here is expensive, and the compounding conditions and The firing conditions are difficult, and there is also the possibility that the addition of 0θ02 may have an unfavorable effect on the properties of the Zr02-Y2O system.

As a result of extensive testing, the present inventor found that it is extremely effective to diffuse carbon into stable specific gravity or partially stabilized zirconia as an alternative to the method of imparting electronic conductivity by adding 0eO2, etc., which has such ridge points. I found that. Accordingly, the present invention relates to mixed conductive zirconia, which is made by fully diffusing carbon into stabilized or partially stabilized zirconia exhibiting ionic conductivity to add electronic conductivity. The present invention also relates to a method for producing such mixed conductive zirconia (the production of mixed conductive zirconia may include stabilization or r/i partially stabilized zirconia sintering or sintering, which exhibits ionic conductivity). Simultaneous 1/
This heat treatment is performed in a carbon atmosphere to form a zirconia sintered body 11.
A method of diffusing this carbon and adding electronic conductivity to it, or a method of molding a mixed powder of zirconia exhibiting ionic conductivity, its stabilizer, and carbon exhibiting electronic conductivity into a predetermined shape and firing it. carried out by.

According to the first mixed L9 method for producing electrically conductive zirconia, a mixed powder containing ZrO2 and about 2 mol% or more of the above-mentioned stabilizer is molded into a predetermined shape,
℃ or higher and then heat-treated in a carbon atmosphere within the same temperature range, or firing and heat-treating in a carbon atmosphere of approximately 1500℃ or higher. It is formed by heating, such as in or in carbon powder.

By such heat treatment in a heated carbon atmosphere, carbon is diffused into the surface and inside of the zirconia sintered body.

4. Also, according to the second mixed conductive zirconia manufacturing method, ZrO2-stabilized side mixed powder of the above formulation is added
About 0.05 to 5% of carbon (average particle size of about 001 to 0.5 μTn) is added to rO2, formed into a predetermined shape, and then heated to about 150% by weight in an inert gas atmosphere.
A method is used in which firing is performed at a humidity of 0° C. or higher, and in this case as well, carbon is uniformly diffused within the zirconia sintered body.

The stable specific gravity or partially stabilized zirconia obtained in this way has the same electronic resistance as carbon (specific resistance 10ffiΩ・α or less) without losing its original properties as a ZrO2 sintered body. can be added. Therefore, by utilizing such electronic conductivity, it is possible to effectively perform electrical discharge machining of a structural material made of a stabilized or partially stabilized zirconia sintered body.

Next, the present invention will be explained with reference to examples.

Example 1 11 mol % of MgO was added to stabilized Z r O2, which was wet mixed and ground in a ball mill and then dried. The dry mixed powder was heated at 48X under the conditions of 1 ton/Cl 1l for 30 seconds.
Pressure molded into a molded body with dimensions of 60 x 4 runs,
This was baked at 1550°C for 2 hours. This sintered body was mounted on a carbon sample stand in a carphone cup equipped with a carbon heater, and heated at 1700 m in vacuum or inert gas.
When the heat treatment is carried out at .degree. C. for 5 hours, carbon vapor is generated from the carbon heater and the like, and carbon is diffused into the surface and inside of the sintered body. In this way〃1. Regarding the treated sintered body, a specific resistance value of 10 mΩ·tyn or less was measured.

A test piece with dimensions of 3 x 4 x 38 + ttwt was cut from the sintered body, and its bending strength (σb) and fracture toughness (K-work) were measured before and after heat treatment in a carbon atmosphere.

) were measured respectively. The results obtained are shown in the following table.

Before surface treatment 6012 After treatment 507 Example 2 3 mol% Y2O3f was added to partially stabilized Z rO2,
This was mixed and ground wet in a ball mill and then dried. This dry mixed powder was pressure-molded in the same manner as in Example 1, and after baking, it was heated to
When the sintered body was fired for several hours, a sintered body having a resistivity of 10 mΩ·cm or less was obtained.

Example 3 3 mol% of Y2O and 1% by weight of carbon (average particle size: 0.03 μm) were added to partially stabilized ZrO2, and the mixture was wet mixed and ground in a ball mill. The dried mixed powder was pressure-molded in the same manner as in Example 1, and baked at 1550°C for 5 hours in a nitrogen atmosphere, resulting in a specific resistance of 10 mΩ.
・A sintered body having a value equal to or lower than that of Senshi was obtained.

agent Patent Attorney Yoshi 1) Toshio

Claims (1)

[Claims] 1. Mixed conductive zirconia made by completely diffusing carbon into stabilized or partially stabilized zirconia exhibiting ionic conductivity to add electronic conductivity. 2. Stabilized or (d) partially stabilized zirconia sintered body exhibiting ionic conductivity is heat-treated in a carbon sintered atmosphere after or simultaneously with sintering to diffuse carbon into the zirconia sintered body (C). Adding T4L child rumor car characteristics 9.
〒Production method of mixed conductive zirconia. 3. A method for producing mixed conductive zirconia, which comprises molding a mixed powder of zirconia exhibiting ion conductivity, a stabilizer thereof, and carbon exhibiting electronic conductivity into a predetermined shape, and firing it.