JPS5833191B2 - Lantern - Cobalt Fukugo Sunkabutsu Shouketsutaino Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a lanthanum-cobalt composite oxide sintered body, and more specifically, to a lanthanum-cobalt composite oxide in which a part of lanthanum or cobalt is replaced with another metal as a solid solution. The present invention relates to a method for manufacturing a sintered body.

Composite oxide sintered bodies of lanthanum and cobalt are used as heat-resistant conductive materials for materials such as MHD power generation electrodes, but the specific resistance changes significantly at high temperatures from room temperature to 1000°C or higher. It has drawbacks such as not necessarily good heat resistance at high temperatures above .degree.

An object of the present invention is to provide a method for producing a lanthanum-cobalt composite oxide sintered body that eliminates the above-mentioned drawbacks, has little change in resistivity from room temperature to high temperature, and has extremely good heat resistance and conductivity. It is about providing.

In order to achieve the above object, the present invention combines each oxide of lanthanum and cobalt with an ion selected from the first group consisting of strontium ion, calcium ion and barium ion, titanium ion, manganese ion, and chromium ion. The lanthanum ions are heated to 700 to 1600°C in an oxidizing atmosphere containing ions selected from the second group consisting of lanthanum ions, iron ions, and nickel ions to transfer 1 to 99% of the lanthanum ions from the first group. A lanthanum-cobalt composite oxide sintered body, characterized in that 1 to 60% of the cobalt ions are replaced in solid solution with an ion selected from the above second group. The gist is the manufacturing method.

The solid solution composition of the lanthanum-cobalt composite oxide can generally be expressed as La1-x-AX-co, -.BiO2.

In the above formula, A is Sr. Either Ca or Ba, and B is Ti, Mn, Zr, or Cr.

Either Fe or Ni, 0.01≦X≦0.99
°0.01≦y≦0.60.

In order to produce the lanthanum-cobalt composite oxide sintered body of the present invention, in addition to lanthanum oxide and cobalt oxide, oxides of metals selected from the above groups, such as strontium carbonate, barium carbonate, manganese carbonate, and Powders of titanium, zirconium oxide, chromium oxide, nickel oxide, etc. are blended in the above composition ratio, mixed uniformly, and heated in air for 70 minutes.
This is carried out by heating at 00 to 1,600°C, preferably 900 to 1,400°C for about 3 hours.

In the present invention, if the humidity does not reach 700°C, sintering will not be performed satisfactorily, and if the humidity exceeds 1600°C, a liquid phase will occur and a stable sintered body will not be obtained. do not have.

In addition, when 1 to 99% of lanthanum ions are solid solution substituted with metal ions selected from the first group, if the amount of substitution does not reach 1% or exceeds 99%, the heat resistance that is the objective of the present invention will not be achieved. Since we want to achieve sufficient improvement in conductivity and electrical conductivity, neither of these is suitable.

Further, in solid solution substitution of 1 to 60% of cobalt ions with metal ions selected from the second group, if the amount of substitution does not reach 1% or exceeds 60%, the object of the present invention is not achieved as described above. This is not appropriate because we want to fully achieve this.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Lanthanum oxide 32.6F, strontium carbonate 118,
IJ, cobalt oxide 58.1F, titanium oxide rice 24.
0.9 and heated at 1150°C for 1 hour.
, 2Sro, 8Coo, 7Tio, and 303 solid solutions were synthesized.

This is finely pulverized and filled into a mold to produce 1 ton/cv.
This was then fired at 1300° C. for 3 hours to obtain a sintered body having a bulk specific gravity of 4.5 and a porosity of 24%.

Apply platinum paint to both end surfaces of the sintered body and leave at room temperature for 5 minutes.
Table 1 shows the results of measuring the specific resistance at 00°C and 1000°C.

Examples 2 to 4 In Example 1, Mn, Zr, and Ni were used in place of Ti, and the results shown in Table 1 were obtained.

Example 5 The results shown in Table 1 were obtained in the same manner as in Example 1 except that the solid solution composition of Co and Ti was changed.

Examples 6 to 7 The results shown in Table 1 were obtained in the same manner as in Example 1, except that some of the Co ions were replaced with Fe ions or Cr ions, respectively, with the solid solution composition shown in Table 1.

Comparative Example Table 1 shows the measurement results of a sintered body obtained in the same manner as in Example 1 except that a solid solution composition of LaCoO3 was used without using strontium carbonate.

As is clear from the results in Table 1, by replacing a portion of La ions with Sr ions, Ca ions, Ba ions, and further replacing a portion of Co ions with Ti ions, Mn ions, Zr ions, etc. , the specific resistance of the obtained sintered body increases and the heat resistance becomes poor.

For example, Lao, 2Sro, and 8CoO3 partially form a liquid phase at 1250°C, but Lao, 2Sro, 3COo, 7Mno, and 30
No. 3 and the like were stable without forming a liquid phase up to 1850°C.

The lanthanum-cobalt composite oxide-containing sintered body obtained by the present invention exhibits high conductivity as shown in Table 1, has little humidity change in resistance, and is stable in an oxidizing atmosphere at high temperatures. Therefore, it is extremely useful as an oxide resistance heating element, a heat-resistant conductive material, etc.

Claims (1)

[Claims] 1 Each oxide of lanthanum and cobalt is combined with an ion selected from the first group consisting of strontium ions, calcium ions and barium ions, and a second ion consisting of titanium ions, manganese ions, chromium ions, iron ions and nickel ions. By heating and firing at 700 to 1600°C in an oxidizing atmosphere containing one kind of ion selected from the group, 1 to 99% of the lanthanum ions are made up of one kind of ion selected from the first group and cobalt ions. 1
A method for manufacturing a lanthanum-cobalt composite oxide sintered body, characterized in that ~60% of the lanthanum-cobalt composite oxide sintered body is subjected to solid solution substitution with one type of ion selected from the second group.