JPH0230620A - High-temperature superconductor - Google Patents

Abstract

PURPOSE:To provide the title superconductor having the critical temperature higher than the boiling point of liquid nitrogen and manifesting superconductivity at ca. 100K, having a specific composition made up of Tl or Pb or Bi, one or two group IIa element(s) except Be and Ra, Cu and O. CONSTITUTION:The objective superconductor represented by the generic formula: AxByCuzOdelta; where A is an element selected from Tl, Pb and Bi, B is one or two element(s) selected from group IIa elements (except Be and Ra), x and y are each real number >0 but <=5, z is real number >=2 but <=4, delta is real number >=1 but <=10. This superconductor is e.g. of the formula Bi3(Ca, Sr)2Cu2 O4.2, Pb2(Ba, Ca)Cu3O6.5, Tl3Ba2Cu2O4, giving zero electrical resistance and having Meissner effect at temperatures at or higher than the boiling point (77K) of liquid nitrogen or near 100K (100 to 120K) and also is a stable substance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to high temperature superconductors, and more particularly to quaternary or quinary oxide superconductors.

[Prior Art] Among oxide superconductors, B i exhibits the highest critical temperature of 100 to 110 K among the substances found so far.
-3r-Ca-Cu-0 system [H,)faeda, Y
.

Tanaka et al: JDn, J, ADl) 1.
PhVs, (1988), to beoubl 1
Including shedl, 90 class Y-Ba-Cu-〇 system [H, Ni, Wu, J, R, ^5hburn et a
t: Phys, Rev.

[J, G.

Bednorz, N.A., Miller: Z., PhVs.
, B64 (1986) 189], many researchers have already investigated the quaternary or quinary materials.
Although the crystal structure and other physical properties have been investigated,
Mainly the Y-Ba-CU-O system. However, although this material does have zero electrical resistance at 90°C, it has problems with stability. For example, oxygen easily escapes (in a vacuum) and superconductivity deteriorates due to its influence on water. On the other hand, the B;-3r-Ca-Cu-0 system has the highest critical temperature and has almost no effect on water, but basic data such as crystal structure is not complete, and the phase exhibiting a high critical temperature (100 to 110 K ＞ and a phase exhibiting a low critical temperature (8
0 to 85 K) coexist, making it difficult to produce a single-phase 100 K class material.

[Problems to be Solved by the Invention] The present invention provides a quaternary to quinary superconductor that is stable, has a critical temperature (Tc> higher than the boiling point of liquid nitrogen (77 K), and exhibits superconductivity near 100 K. The problem to be solved is to donate one's body.

[Means to solve the problem] According to the invention, the following general formula: %formula% (however, A is MB group TI, IVb group Pb of the Periodic Table of Elements.

One element selected from Vb group 3i B is one or two elements selected from Group 1a (excluding Be and Ra) of the periodic table of elements Cu is group Ib of the periodic table of elements CIJ O is group Vlb of the periodic table of elements O x , y is a real number greater than O and less than or equal to 5. 2 is a real number greater than or equal to 2 and less than or equal to 4. δ is a real number greater than or equal to 1 and less than or equal to 10. ) is provided.

A specific example of a high temperature superconductor represented by the above general formula is:
B 13 (Ca, S r )2 CCl204.2
Pb2 (Ba, Ca) + CCl20s, s, T I
38az Cuz 04, etc., and all of them have the characteristics of being stable substances with zero electrical resistance and complete diamagnetism (Meissner effect) at the boiling point of liquid nitrogen (77K> or above, or around 100K>100~120K>). have

The high temperature superconductor of the present invention can be produced by various methods. For example, the oxides, carbonates, etc. of the above-mentioned elements are mixed into a fine powder using a dry method or a wet method. Next, it is calcined at a desired temperature and for a desired period of time in a furnace having a normal atmospheric atmosphere or an atmosphere with a controlled oxygen partial pressure. After cooling to room temperature, the mixture is carefully pulverized and mixed, then pressure molded at a pressure equivalent to about 30 kg/CIi, and fired at a predetermined temperature and time.

Further, as a thin film manufacturing method, a wet method such as a screen printing method, a sputtering method, a molecular beam epitaxial method, a plasma spraying method, etc. can be used. In addition, some of these manufacturing methods can be improved by optimizing the manufacturing conditions.
Some materials can obtain initial characteristics at a relatively low temperature of about 0° C. or lower.

In these methods, by selecting the type and properties of the substrate, it is possible to improve the performance of the product through the effect of epitaxy. Further, the properties of the product can be improved by subjecting it to a rough heat treatment under the above-mentioned firing conditions.

The superconductor thus obtained has good electrical conductivity and exhibits superconductivity when cooled below a critical temperature. In other words, at this time, completely conductive, completely diamagnetic,
This shows the Josephson effect.

[Example] Next, the present invention will be explained with reference to Examples.

Example 1 Each powder of PbO, BaCO3, CaCO3, cuo,
They were mixed in a ratio of Pb:Ba:Ca:Cu=2:1:1:2, and calcined at 830 to 850°C for 12 hours. After crushing and mixing this, a hydraulic molding machine is used to
Apply a pressure of 0kL/7, diameter 20mm.

After molding to a thickness of 3 mm, it was annealed at 850° C. for 10 hours, and then slowly cooled to room temperature.

When the electrical resistance was measured using the 4-terminal method, it was approximately 102
When the electrical resistance became O at K, and the AC magnetic susceptibility was investigated,
The Meissner effect was observed at the same temperature.

Example 2 Powders of TI203, BaCO3, and CuO were mixed into T1:Ba
:CLJ=2:2:3 and mixed. After calcining in an electric furnace at 880°C for 10 hours, it is thoroughly crushed.
Mixed. Then, it was molded in the same manner as in Example 1. After baking this at 880° C. for 12 hours, the electrical resistance was measured using the 4@son method, and the electrical resistance was found to be O and the Meissner effect at about 85°C.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, a stable high-temperature superconductor with a critical temperature equal to or higher than the boiling point of liquid nitrogen, exhibiting complete diamagnetism (Meissner effect) in electrical resistance O1, can be obtained. It will be done.

Claims (1)

[Claims] The following general formula: A_xB_yCu_zO_δ (However, A represents Group IIIb Tl, IVb Group Pb, Vb Group B of the Periodic Table of Elements)
One element B selected from i is selected from Group IIa of the Periodic Table of the Elements (excluding Be and Ra) Cu is one or two elements selected from Group IIa of the Periodic Table of the Elements Cu is Group VIb of the Periodic Table of the Elements O is Ox, Group VIb of the Periodic Table of the Elements y is a real number greater than 0 and less than or equal to 5. z is a real number greater than or equal to 2 and less than or equal to 4. δ is a real number greater than or equal to 1 and less than or equal to 10. ) is a high-temperature superconductor represented by