JPH01179752A - Production of superconducting ceramic - Google Patents

Abstract

PURPOSE:To obtain a superconducting ceramic having high critical temp., stable characteristic, and improved reliability by calcining a mixture of RE-Ba-Cu-O at a specified temp. in O3 atmosphere or O2+O3 atmosphere. CONSTITUTION:A herein RE mean rare earth elements, mixture consisting of (RE)2O3, BaCO3, CuO, etc., with a specific ratio, is calcined at 930-1,000 deg.C in O3 or O3+O2 atmosphere, then cooled at a desired cooling rate. In the case that (RE)2O3 is Y2O3 and mixing ratio of Y:Ba:Cu is 1:2:3, obtained ceramic by this method has higher Tc than that calcined in only O2 atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing superconducting ceramics with a high critical temperature.

[Prior art] Conventionally, as a superconducting material, for example, Japanese Patent Application Laid-Open No. 57-8594
As typified by the one disclosed in Publication No. 4, Nb or an Nb-based alloy such as Nb3Sn has been used in many cases.

However, in the conventional superconducting materials using Nb or Nb-based alloys, the temperature at which the superconducting state returns to the normal conducting state, that is, the critical temperature Tc, is as low as 10 to 20. In order to use a superconductor using Nb or a Nb-based alloy in a superconducting state, the superconductor must be placed in an extreme environment below the critical temperature Tc, and for this reason, it is necessary to use, for example, a helium liquefaction refrigerator. .

Therefore, the equipment costs including the helium liquefaction refrigerator and the heat insulating structure and the operating costs are very high, and the reliability of the equipment cannot be maintained because it is used in an extreme environment.

In order to solve this drawback, I
? BACKGROUND ART Superconducting ceramics based on E (rare earth element) -Ba-Cu-○ have been developed, and some have appeared to have a critical temperature Tc of about 90°C. The manufacturing method of these superconducting ceramics is described, for example, in the literature Japanese,
Journal of Applied Physics (JAP)
ANESE JOURNAL of APPLIEDP
HYSIC3, VOl, 2B, No, 8.1987.
oxides of rare earth elements RE, as described in Li2O2 (page).

A mixture of BaC0a and CuO was heated to 900°C to 100°C.
The method involved firing in air or in an oxygen (02) atmosphere at a temperature of 0°C.

[Problems to be Solved by the Invention] However, the critical temperature Tc of superconducting ceramics produced by the above manufacturing method tends to vary due to subtle differences in firing temperature, atmosphere, etc. There was a problem that it was difficult to manufacture.

This invention was made to solve these problems, and an object thereof is to provide a method for manufacturing superconducting ceramics that can produce stable superconducting ceramics with high critical temperature Te with good reproducibility. It is.

[Means for solving the problems] The method for manufacturing superconducting ceramics according to the present invention is based on RE (
Rare earth elements Sc, Y, La, Nd, Sm, E
u.

Gd, Dy, Ho, Er, Tm,
In producing superconducting ceramics containing Yb, Lu), Ba, Cu, and O, (RE) OBa
After mixing C03 and CuO in a predetermined component ratio 2 3', heat at 930°C to 10 in 03 atmosphere or O2 + O3 atmosphere.
It is characterized by being fired in a temperature range of 00°C.

[Function] In the present invention, superconducting ceramics having a stable and high critical temperature Tc can be obtained by firing (RE) Ba-Cu-0 based superconducting ceramics in an 03 atmosphere or an O2+O3 atmosphere. Ta.

Therefore, the above problems can be solved.

[Example] Hereinafter, as an example of the present invention, Y is added to the rare earth element 17E.
The case of creating superconducting ceramics made of Y1Ba2Cu3ox will be described.

y2o3. +3aC03,CuO as Y, Ba, C
The composition ratio of u] was weighed so as to be 2.3, and each composition was mixed in a mortar until it became uniform. This mixed powder was pre-sintered in air at 900°C for 5 hours to produce a pre-sintered powder.

This calcined powder was crushed using a ball mill and then molded using a press to produce a plurality of sample pellets each having a diameter of 10 mm and a thickness of 3 mm.

This sample was placed in an O atmosphere and an atmosphere of 95
It was baked at 0°C for 10 hours. Here O+03 atmosphere is 02
This was achieved by introducing the gas into the furnace after passing it through an ozone generator. Each sample was fired at ]°C/min, 2°C/min.
Superconducting ceramics were fabricated under different firing conditions by cooling at five cooling rates: 10°C/min, 4°C/min, 6°C/min, and IO°C/min.

Critical temperature T of superconducting ceramics with different firing conditions
In order to investigate c, each sample after firing was placed in a refrigerator for 20 minutes.
Before cooling to K, the change in electrical resistivity of each sample was measured by a four-terminal resistance measurement method. Then, the temperature at which the measured value of electrical resistivity became 1.0×10 −6 Ω·0 m or less was observed as the critical temperature Tc. Table 1 shows the critical temperature Tc of each sample observed.

Table 1 As is clear from Table 1, the samples fired in the 02 + Os atmosphere showed a higher critical temperature Tc at all cooling rates than the samples fired in the 02 atmosphere. Further, the critical temperature Tc of the sample fired in the 02 atmosphere varies greatly from 83K to 89K depending on the cooling rate. However, the critical temperature Tc of the sample fired in the 02 + 03 atmosphere was within the range of 87K to 94K even if the cooling rate was different, and a stable critical temperature Tc could be achieved.

In addition, in the above example, the case where the firing temperature was 950°C was explained, but the firing temperature was changed to 9308°C to 10°C.
Even if the sample was fired in an O2+O3 atmosphere with the temperature changed within the range of 00°C, a stable and high critical temperature Tc could be achieved as in the above example.

Also, rare earth element 1? Sc, La instead of Y as E
.

Nd, Sm, Eu, Gd, Dy,
Superconducting ceramics using Ho, Er, Tm, Yb or Lu are placed in an O2+O3 atmosphere or 03
Even when the film was produced by firing in an atmosphere, a stable and high critical temperature Tc could be achieved similarly to the above embodiment.

[Effects of the Invention] As explained above, according to the manufacturing method of the present invention, RE-Ba-
Compared to Cu-0-based superconducting ceramics, it was possible to produce superconducting ceramics having a stable and high critical temperature Te that is less affected by firing conditions.

In addition, since the critical temperature Tc is less affected by firing conditions,
We were able to fabricate highly reliable superconducting ceramics with good reproducibility.

Claims (1)

[Claims] In the method for manufacturing RE-Ba-Cu-O-based superconducting ceramics, firing is performed in an O_3 atmosphere or in an O_2+O_3 atmosphere.
A method for producing superconducting ceramics, characterized in that the process is carried out in an atmosphere at a temperature range of 930°C to 1000°C.