JPH0688831B2 - Method for manufacturing superconducting ceramic material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a Y-Ba-Cu-O superconducting ceramic material, and particularly, to optimize the temperature change treatment in the sintering step of the material, The present invention relates to a method for obtaining a Y-Ba-Cu-O superconducting ceramic material having a characteristic that a superconducting state can be obtained at a liquid nitrogen temperature or higher.

[Prior Art] In the case of La-Ba-Cu-O-based and La-Sn-Cu-O-based superconducting ceramic materials, these materials are placed in a furnace preheated to a temperature of 900 to 1000 ° C. The sintering process was carried out by holding the material for a predetermined time, removing it from the furnace, and cooling it in air. However, Y-Ba-Cu-O superconducting ceramic materials do not exhibit superconductivity in the liquid nitrogen temperature range by this method.

[Problems to be Solved by the Invention] In the present invention, the sintering treatment method of the above-mentioned superconducting ceramics material has been earnestly studied, and a sintering treatment method capable of obtaining a superconducting state at a liquid nitrogen temperature or higher has been found. . That is,
An object of the present invention is to provide a manufacturing method by a sintering process which can obtain a Y-Ba-Cu-O superconducting ceramic material which can be in a superconducting state at a temperature of liquid nitrogen or higher.

[Means for Solving Problems] In order to obtain the superconducting ceramic material as described above, the present invention provides a step of sintering a superconducting ceramic material in a method for producing a Y-Ba-Cu-O superconducting ceramic material. The cooling rate of the cooling process at 125 ℃ / hour ~ 150 ℃
The method for producing a superconducting ceramics material is characterized in that the superconducting ceramics material is produced in the range of / hour.

[Constitution of the Invention] Compared to the La-M-Cu-O system (M = Ba or Sn), M-Ba-
There are various possible reasons why the Cu-O-based (M = IIIA group element) superconducting ceramic material does not exhibit superconductivity above the liquid nitrogen temperature. One of them is the heat treatment method.
The present invention pays attention to this point, and the M-Ba-Cu-O system (M = II
This is the result of repeated research on the heat treatment method for superconducting ceramic materials (Group IA elements).

That is, when the Y-Ba-Cu-O superconducting ceramics material of the present invention is manufactured, the raw material powder is molded and hardened, that is, sintered, but by controlling this cooling step,
It was discovered that a material having a superconducting displacement point above the liquid nitrogen temperature can be obtained.

According to the method for producing a superconducting ceramic material of the present invention, Y
-Ba-Cu-O superconducting ceramics by performing the cooling rate in the cooling process in the sintering process in the range of 125 ℃ / hour to 150 ℃ / hour. The material was obtained. That is, the superconducting ceramic material obtained at a temperature lowering rate of less than 125 ° C / hour has a superconducting displacement point at a temperature lower than the liquid nitrogen temperature, and at a temperature lowering rate of more than 150 ° C / hour,
Sintered superconducting ceramic materials have no superconducting displacement point above the liquid nitrogen temperature. For the above reasons, in the method for producing a superconducting ceramic material according to the present invention,
It is important to perform cooling after the sintering process at a temperature lowering rate in the range of time to 150 ° C / hour.

Next, a method for producing the superconducting ceramic material of the present invention will be shown by a specific example.

Sintering conditions were investigated for Y-Ba-Cu-O superconducting ceramic materials.

In order to obtain a Y-Ba-Cu-O superconducting ceramic material, it is known that the material is sintered at about 900 ° C to 1000 ° C, and the sintered material exhibits superconductivity. The inventors considered that the characteristics of the superconducting ceramics material were determined by the heat treatment step of this material, and tried to find the optimum one for the firing heating and cooling step conditions. There are various conditions in the firing and heating process, and it is not known which of them affects the properties of the produced material. Sintering temperature, holding temperature, rate of temperature increase, rate of temperature decrease, atmospheric conditions, etc. affect intricately,
It determines the characteristics of the sintered material. The holding temperature for sintering the Y-Ba-Cu-O superconducting ceramics material is 900 ℃.
It is said that ~ 1000 ° C is optimal. In the present invention, other sintering treatment conditions were studied. That is, the following research was conducted.

The composite oxide of Y-Ba-Cu-O was applied at 25 ° C / hour, 50 ° C / hour, 75 ° C / hour, 100 ° C / hour, 125 ° C / hour, 150 ° C / hour,
Sintering was performed at the same heating rate and cooling rate under eight conditions of 175 ° C / hour and 200 ° C / hour. The superconducting characteristics of each superconducting ceramic material obtained by the sintering treatment under each condition were measured. The results are shown in Table 1.

The sintering holding temperature was 900 ° C and the holding time was 2 hours.

Next, it was assumed that what determines the superconducting characteristics of the superconducting ceramic material was not the heating rate but the cooling period, and only the cooling rate was changed, and experiments were conducted. That is, the heating rate is fixed at 150 ° C / hour, and the cooling rates are 25 ° C / hour, 50 ° C / hour, 75 ° C / hour, 100 ° C time, 125 ° C / hour, and 150 ° C / hour, respectively.
The superconducting properties of the obtained superconducting ceramic material were measured by performing a sintering process under eight conditions of ℃ / hour, 175 ℃ / hour, and 200 ℃ / hour. The results are shown in Table 2.

From the measurement results of the superconducting properties shown in Tables 1 and 2 above, it was clarified that the superconducting properties of the ceramic material were greatly affected by the cooling rate.

From the above measurement results, in the Y-Ba-Cu-O superconducting ceramics material, in order to obtain the superconducting transition temperature above the liquid nitrogen temperature, the temperature decreasing rate in the sintering process was 125 ° C / hour to 150 ° C / hour. It was found that the optimum condition was.

[Advantages of the Invention] The present invention provides a superconducting ceramic material having excellent superconducting properties by the sintering treatment method of Y-Ba-Cu-O according to the present invention, that is, a superconducting transition temperature higher than liquid nitrogen temperature. It is possible to provide a manufacturing method capable of manufacturing an M-Ba-Cu-O-based (M = IIIA group element) superconducting ceramics material capable of producing the above-mentioned remarkable technical effects.

Claims (1)

[Claims] 1. A method for producing a Y-Ba-Cu-O superconducting ceramic material, wherein the cooling rate in the step of sintering the superconducting ceramic material is set in the range of 125 ° C./hour to 150 ° C./hour. The method for producing a superconducting ceramics material described above.