JPS62138359A - Ceramic sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel high-strength ceramic material that has unprecedentedly low thermal conductivity and electrical conductivity.

[Problems to be solved by conventional technology/inventions] Conventionally, high-temperature materials with excellent insulation properties and electrical conductivity have been achieved by mixing electrically conductive fillers into insulating fibers. has been done. However, its mechanical strength is extremely low, and it has the disadvantage that it cannot be used as a structural material.

In view of the current situation, it is an object of the present invention to provide a heat-insulating and heat-resistant material that has excellent mechanical strength as well as electrical conductivity.

[Means for solving problems]

In order to achieve the above object, the present inventors investigated various materials and found that a ceramic sintered material having a thermal conductivity of 5 W/mK'c or less, an electrical conductivity of 10107- or more, and a relative density of 90% or more was used. This is what I found.

That is, the present invention has ZrO2 as the main component, and 10 to 40 volume percent of one or more carbides, nitrides, and carbonitrides of elements in Groups ■a, Va, and Ma of the periodic table as the second component; Contains 0.1 to 1 Q and 0 weight percent of the second component of an oxide of the same element as the metal element of the second component, and has a thermal conductivity of 5 W/mK'c or less and an electrical conductivity of 101 υb or more, It is a ceramic sintered body having an average particle size of 2μ or less and a relative density of 90% or more. Particularly preferred embodiments of the invention include the ceramic sintered bodies described above, which contain a stabilizer in which Zr% is selected from oxides of elements of the Ina group, CaO or MgO, which exhibit excellent mechanical properties. More preferably, it contains 2 to 5 mol percent of Y2O3 as a stabilizer, and ZrO2
The ceramic sintered body has high strength and has a tetragonal crystal phase.

The present invention consists of a sintered body in which ZrO is the main constituent phase, and a part of it is replaced with a carbide, nitride, or carbonitride of an element of group Ia, Va group, or Ma group of the periodic table.

By using ZrO2 as the main constituent phase, it is possible to obtain strength and heat insulation properties. Preferably Y2O, CaO
Alternatively, ZrO□ containing 2 to 5 moles of a stabilizer selected from MgO is used. In addition, such ZrO□
The powder is preferably a fine, uniform powder obtained by a coprecipitation method. If the amount of the stabilizer is less than 2 moles, monoclinic crystals will form in the sintered body and cracks will occur, and if it is present in excess of 5 moles, the strength of the sintered body will be reduced. Particularly preferably, ZrO2 containing about 3 mol percent of Y2O3 and exhibiting a tetragonal crystal structure in the sintered body is used, whereby high strength can be obtained. Such ZrO□ powder is already known as partially stabilized zirconia.

A carbide, nitride or carbonitride of group F/ a % Va − of the periodic table is added as a second component in order to obtain electrical conductivity, and the amount added is 10 to 40 percent by volume. If the content is less than 10% by volume, the electrical conductivity will be insufficient, and as will be described later, each preferable characteristic value of the sintered body of the present invention can be achieved by setting the content to 40% by volume or less.

Further, the second component preferably has a particle size of 2μ or less,
Particularly preferably, one having a thickness of 1 μm or less is used. This is because the smaller the particle size, the higher the electrical conductivity; if the particle size exceeds 2μ, the electrical conductivity is low and furthermore, only a sintered body with low mechanical strength can be obtained.

As for the carbides and nitrides of group IVa, Va, and Va of the periodic table, TiO is preferable from the viewpoint of raw material cost and properties of the obtained sintered body, but TagXWe, TiN, and TaN are also preferable.

Alternatively, excellent performance can be obtained even with a mixture such as TiON.

In addition to the above-mentioned main component and second component, an oxide of the same metal element as the second component is further added at α1 to 10% by weight. This is effective in improving sinterability, reducing thermal conductivity and improving electrical conductivity, and the amount added is i.
If the amount is less than 1% by weight, the effect will be small, and if it is added more than 10% by weight, the strength of the sintered body will be greatly reduced and is not suitable.

After mixing the Zr0-powder as described above, particularly preferably the ZrO2 powder containing an appropriate amount of a stabilizer, the second component to be added and the powder of an oxide of the same metal element as the second component in a conventional manner, the mixture is subjected to embossing sintering. (hot press), hot isostatic press, inert gas atmosphere sintering, vacuum sintering, etc. to form a dense sintered body.

Further, the characteristics of the sintered body of the present invention obtained as described above are that the thermal conductivity is 5 w/mK'c or less, and the electrical conductivity is 10 ηi or more. ■Thermal conductivity and electrical conductivity vary greatly depending on the content of second components such as carbides, nitrides, and carbonitrides of aSVa and Ma group elements, but the above characteristic values are achieved at a content of 10 to 40 volume percent. get. Also, grain size,
The influence of the sintered body density is also large, and the average grain size must be 2 μ or less, and the sintered body density must be 90% or more in relative ratio.

By satisfying these requirements, high-strength ceramics with excellent heat insulation and conductivity can be obtained. As mentioned above, the zirconium oxide powder is preferably a fine uniform powder produced by a coprecipitation method. It is preferable to use powders of carbides, nitrides, etc. that have been thoroughly ground and have an average particle size of 2 μm or less.

〔Example〕

Example 1 Powder blended with the composition shown in Table 1 was hydrostatically pressed at a pressure of 2 t/cJ and sintered in vacuum at a temperature of 1500° C. for 2 hours. Carbide and nitride powders are pre-treated with carbides and nitrides.
An oxide powder of the same metal element as the nitride was added in an amount of 2.0% by weight.

From each sintered body obtained, S wi X A m X 4
For each piece cut out to the size of G ym, the density is 3
Point bending strength, thermal conductivity, electrical conductivity and particle size were measured. The above results are also summarized in Table 1.

From the results in Table 1, it is clear that the sintered bodies of the present invention of S1-6, 9.11, and 12 are high-strength materials with excellent heat insulation properties and electrical conductivity.

Example 2 A sintered body was obtained under the same conditions as in Example 1 using powder blended with the composition shown in Table 2, and each characteristic value was measured in the same manner. The obtained results are also summarized in Table 2.

Looking at the results in Table 2, the effect of adding α1 to 100% by weight of the oxide TiO2 of the same metal element to the second component ie can be clearly understood.

〔Effect of the invention〕

The ceramic sintered body of the present invention is a novel material that is heat resistant, has low thermal conductivity, that is, excellent heat insulation, has electrical conductivity, and also has high strength.

The ceramic sintered body of the present invention is very advantageous because it can be used as a material that requires the above-mentioned properties, such as an electrode material used at high temperatures, and has excellent strength.

Claims (3)

[Claims] (1) ZrO_2 as the main component, and 10 to 40 volume percent of one or more carbides, nitrides, and carbonitrides of group IVa, Va, and VIa elements of the periodic table as the second component;
Containing an oxide of the same element as the metal element of the second component in an amount of 0.1 to 10.0 weight percent of the second component,
Thermal conductivity is 5W/mK°C or less, electrical conductivity is 10^1■
/cm or more, an average particle size of 2μ or less, and a relative density of 90% or more. (2) The ceramic sintered body according to claim (1), wherein ZrO_2 contains a stabilizer selected from oxides of group IIIa elements, CaO, or MgO. (3) Claim (1) characterized in that it contains 2 to 5 mol percent of Y_2O_3 as a stabilizer.
The ceramic sintered body described in item or item (2).