JPH0333052A - Production of oxide superconducting material - Google Patents

Abstract

PURPOSE:To obtain the material having a higher superconductivity critical temp. by mixing the oxide powders contg. Tl, Pb, Ca, Ba and Cu in a specified atomic ratio and sintering the mixture under specified conditions in an oxygen atmosphere. CONSTITUTION:The oxide powders contg. Tl, Pb, Ca, Ba and Cu are mixed in the atomic ratio of Tl:Pb:Ca:Ba:Cu=r:s:3:1:3 (where 0.5<r<1 and 0<s<0.5). The mixture is sintered at 820-950 deg.C for 6-100hr in an oxygen atmosphere. An oxide superconducting material having a high critical temp. is obtained by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing oxide superconducting materials. More specifically, having a high superconducting critical temperature ('re),
The present invention relates to a method for manufacturing Tl-based superconducting materials.

Conventional technology In 1986, Bednorz and Muller et al. discovered complex oxide-based superconducting materials with high Tc, greatly opening up the possibility of high-temperature superconductivity (Bednorz, Muller, "Z, Phys.
s, 864 (1986) 189”).

The oxide superconductor discovered by Bednotes and Muller et al. is (La, Sr) 2Cu O, and this oxide superconductor is called a K2NiF type oxide, which is a type of perovskite superconductor that has been known for a long time. Although its crystal structure is similar to that of oxides, its Tc is approximately 30, which is significantly higher than that of conventional superconducting materials.

Furthermore, in February 1987, 9
Y1Ba2Cu3O7-x exhibiting a class critical temperature of 0
The discovery of a complex oxide has been reported in the newspapers, and the possibility of realizing non-low-temperature superconductors has suddenly increased.

In 1988, it was reported that TI-Ba-Ca-Cu-0 based composite oxide Tc, which does not use rare earth elements and whose raw materials are relatively inexpensive, may have a Tc of over 100K. It is known that a plurality of phases having different critical temperatures exist in a TI-Ba-Ca-Cu-0 based composite oxide superconductor. To form only the high temperature phase, pb
There are also announcements that it is effective to add TI+, 53Ptlo, sBa, Ca,...
Cun○8 (Tlo, 5Pbo, 2) 1.25
(eao, 5Cao, s) It has also been reported that a composite oxide represented by aca3cu4011 exhibits superconductivity at high temperatures. (Science Vol, 241p
p1198-1200) Furthermore, patent application No. 63-285538 by the patent applicant of this application
The issue contains elements AIEI selected from group IIa of the periodic table.
An oxide superconducting material is disclosed that contains AIE2, Tl, pb, and Cu, and is represented by the -class formula % (where 0<x<1, n≧2). . In addition, in Japanese Patent Application No. 1-35661 filed by the applicant for the present patent,
Tl5
Oxide powder containing Pb, Ca5Ba and Cu is prepared with an atomic ratio Tl:Pb:Ca:Ba:Cu=r:s:
3: 1:3 (however, Q, 5<r<1, 0<s<0
．． 5) Mix at a ratio of 820~ in an oxygen atmosphere.
A method for producing an oxide superconducting material is disclosed, which is characterized by sintering at a temperature of 950° C. for 6 to 100 hours.

Problems to be Solved by the Invention However, in the TI-Ba-Ca-Cu-0 system superconductors, several types of superconductors such as Tl□Ca, , Ba2Cu, 08 system and Tl, CaBa, C'u20° system exist. Although a high Tc phase has been obtained with a critical temperature as high as 120, it is difficult to generate a single high Tc phase.

Furthermore, in the Tl-based composite oxide superconducting material, TI has a high vapor pressure among the constituent elements, and TI scatters during the manufacturing process, making it difficult to precisely control the composition.

Therefore, an object of the present invention is to provide a method for producing a TI-based superconducting material having a higher superconducting critical temperature than conventional ones.

Means for solving the problem According to the invention, Tl, Pb, Ca, Ba and C
The atomic ratio of oxide powder containing u is Tl:Pb:Ca:
Ba:Cu=r:s:3:l:3 (however, Q
, 5<r<1, 0<s<0.5),
6-100 at a temperature of 820-950℃ in an oxygen atmosphere
Provided is a method for producing an oxide superconducting material characterized by time-sintering.

Function: The method for producing an oxide superconducting material of the present invention is based on the following formula: This is a method of manufacturing. This oxide superconducting material has 10-20% of the TI sites as p
b, and it is possible to obtain the above various phases with different C-axis lengths in a single phase while maintaining the structure of one (Tl, Pb)-0 layer. be.

In the manufacturing method of the present invention, when pb is not added, a structure in which there is only one (Tl, Pb)-0 layer is not adopted, and pb is not added.
If the amount of b added exceeds 50% of the amount of TI, an impurity phase will precipitate. Therefore, in the manufacturing method of the present invention, rSs is Q, 5< r < 3 Q < s < 0.5, respectively.
is preferred.

Furthermore, if the sintering temperature is less than 820° C. or the sintering time is less than 6 hours, the reaction will not be sufficiently carried out and an impurity phase will remain. If the sintering temperature exceeds 950°C, a liquid phase will be generated during sintering, and impurities will also be generated.

Furthermore, the above sintering reaction was completed within 100 hours, and 1
There is no difference in the properties of the obtained superconducting material even if the sintering time exceeds 00 hours. Therefore, in the method of the present invention, a superconducting material is manufactured under the above conditions.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention in any way.

Example raw materials include Tl□03, PbO, CaO, BaO2, C
Each powder of uO was converted into Tl :Pb :Ca :Ba :Cu
The ratio is ■ 0.8:0.2:3:l:3■
0.75 : 0.25 : 3 : 1 : 3 ■ 0
．． 8:0.2:3:1:3■ 0.95:0
．． 05: 3: 1: 3 ■ 0.95: 0.
05:3:1:3, respectively, and pelletized at about 100 kg/caf. Each pellet is wrapped in 50 micron thick Au foil and the flow rate is 200mj! 1 at different temperatures ranging from 850 to 900 °C, respectively, in a furnace with a gas flow of 02/min.
The superconducting material of the present invention was produced by sintering for 0 hours.

The characteristics of each superconducting material obtained are shown in Table 1, the X-ray diffraction data are shown in FIGS. 1 to 5, and the magnetic susceptibility measurement results are shown in FIGS. 6 to 10.

As described in detail, the oxide superconducting material produced by the production method of the present invention has a high critical temperature and can be effectively used in the fields of superconducting cables, electronic materials, etc.

[Brief explanation of drawings]

Figures 1 to 5 are X-ray diffraction patterns of samples ■ to ■, respectively, in Examples of the superconducting material of the present invention, and Figures 6 to 10 are X-ray diffraction patterns in Examples of the superconducting material of the present invention. These are the measurement results of magnetic susceptibility of samples ① to ②, respectively.

Claims (1)

[Claims] Oxide powder containing Tl, Pb, Ca, Ba and Cu has an atomic ratio of Tl:Pb:Ca:Ba:Cu=r:s:3:
It is characterized by mixing at a ratio of 1:3 (however, 0.5<r<1, 0<s<0.5) and sintering at a temperature of 820 to 950°C for 6 to 100 hours in an oxygen atmosphere. A method for producing an oxide superconducting material.