JPH02201819A - Compound superconductive material and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the strength of attachment of oxide superconductive material to a coating material, substrate material, etc., and improve the mechanical strength by forming a layer of oxide superconductive layer through a middle reaction layer on a base body of platinum or platinum alloy. CONSTITUTION:An oxide superconductive material is heated up to over its fusing point to be fused, and the molten matter is applied on a layer of platinum or platinum alloy of a base body 1. Or otherwise the powders of the oxide superconductive material are applied on the layer of platinum or platinum alloy of the base body and then heated up to the fusing point of the oxide superconductive material to be fused. For applying the heated and fused oxide superconductive material, the base body is immersed in the fused material, or the fused material is applied through a nozzle provided in a lower part of a heat crucible. The oxide superconductive material over the fusing point on the layer of platinum or platinum alloy reacts with platinum and forms a middle reaction layer 3 which is dense and strongly connected with the base body. By then hardening the molten matter of the oxide superconductive material to crystallize it, a layer 2 of the oxide superconductive material is formed.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a compound superconducting conductor using an oxide superconductor and a method for producing the same.

(Prior art) Many superconducting materials whose electrical resistance becomes zero below a certain temperature have been discovered, and various attempts have been made to use them to create superconducting wires and superconducting electronic devices. There is.

In addition, various so-called high-temperature superconductors having transition temperatures higher than the boiling point temperature of liquid nitrogen have recently been discovered, and attempts to realize superconducting wires and superconducting devices that do not require expensive liquid helium have attracted interest.

Examples of the high-temperature superconductor include defective perovskite-type oxide superconductors having oxygen defects such as the Y-Ba-Cu-0 system, and B1-8r-Ca-
Cu-0 based and Tl-Ba-Ca-Cu-0 based oxide superconductors have been discovered. Among these high temperature superconductors,
Ba-based and TI-based oxide superconductors are heated at 110K or 80K.
It not only has a high critical temperature, but also has the advantages of not requiring rare earth elements, which are scarce in resources, and being stable against moisture and not causing any deterioration of properties such as critical temperature or critical current density. Therefore, it is considered to be practically advantageous compared to oxide superconductors such as Y-based superconductors.

By the way, when trying to use these oxide superconductors to construct conductors used in superconducting magnets, superconducting electronic devices, etc., it is difficult to make wires by themselves due to the inherent brittleness of these oxide superconductors. There's a problem. Therefore, practical use is progressing as a composite material with coating materials and substrate materials made of metals that have excellent workability, high strength, and low specific resistance.

Such coating materials and substrate materials not only increase the strength against external forces, but also serve as a current path when the superconducting state is broken, and prevent burnout that would occur when a large current flows through the oxide superconductor in the normal conducting state. It also functions as a stabilizing material.

At present, silver is often used as the coating material or substrate material because of its ability to supply oxygen to the oxide superconductor and its stability when heat treated at high temperatures. For example, attempts have been made to form long wires or tapes by filling a silver tube with oxide superconductor powder and drawing the tube to a predetermined diameter or shape.

(Problem to be Solved by the Invention) However, the superconducting wire or superconducting tape material produced by filling the silver tube with oxide superconductor powder and then drawing the tube, as described above, does not have the inner wall of the chain tube and the oxide superconductor layer. Since these are only in mechanical contact, when external stress such as bending is applied to these, cracks and peeling are likely to occur, especially in tape materials, which deteriorates superconducting properties such as critical current density. There was a problem.

The present invention has been made to address the problems of the prior art, and provides a compound superconductor and a compound superconductor with improved mechanical strength by increasing the bonding force between the oxide superconductor and the covering material, substrate material, etc. The purpose of this invention is to provide a manufacturing method for the same.

[Structure of the Invention] (Means for Solving the Problems) That is, the compound superconducting conductor of the present invention comprises a substrate having a platinum or platinum alloy layer on at least the surface, and a platinum and oxidized layer on the platinum or platinum alloy layer of the substrate. It is characterized by having an oxide superconductor layer formed via an intermediate reaction layer containing a compound with a constituent element of the oxide superconductor.

Furthermore, the method for producing a compound superconducting conductor of the present invention includes heating and melting an oxide superconductor or a mixture that becomes an oxide superconductor by heating, and then applying the melt onto a substrate having a platinum or platinum alloy layer on at least the surface. or after coating the oxide superconductor or the mixture that becomes an oxide superconductor by heating on the platinum or platinum alloy layer of the substrate, the oxide superconductor or the mixture that becomes an oxide superconductor by heating. It is characterized in that it is heated and melted, and then the melt is crystallized to form an oxide superconductor layer.

Many oxide superconductors are known, but
In the present invention, an oxide superconductor having a perovskite structure containing rare earth elements, B1-8r-Ca-Cu
-0 series oxide superconductor, Tl-Ba-Ca-Cu-0 series oxide superconductor, etc. are applied.

The oxide superconductor containing a rare earth element and having a perovskite structure may be one that can realize a superconducting state, for example, LnM CuO system (L
n is Y, La, Sc, Nd, SLl.

237-δ Eu, Gd5Dy, llo, Er, Ti, Yb
, at least 1 selected from rare earth elements such as Lu.
A seed element, M is at least one element selected from Ba, Sr, and Ca, δ represents an oxygen defect and is usually a number of 1 or less, a part of Cu is TI, V SCr% Mns Pe,
, 00% Can be replaced with Nl, Zn, etc. ) are exemplified. Rare earth elements are broadly defined as Sc,
It shall include Y and La systems.

In addition, the B1-9r-Ca-Cu-0-based oxide superconductor has the chemical formula % formula % () B12 (Sr, Ca) 3 Cu3 0x
----------(II) (In the formula, part of the former can be replaced with pb, sb, etc.), etc., and is a T l-Ba-Ca-Cu-0 system. Oxide superconductors are represented by the chemical formula % ().

Further, the substrate used in the present invention has a platinum or platinum alloy layer on at least the surface, and specific forms include: (1) platinum or Au-Pt alloy, Ag-Pt alloy, Pd
- A substrate made of various platinum alloys such as a pt gold alloy or a Rh-Pt alloy.

■ A layer of platinum or the above-mentioned platinum alloys is formed on the surface of a metal substrate such as copper or nickel.

Examples include. The metal substrate in the form (■) above is one that is stable at the temperature at which the oxide superconductor is melted, and a layer of platinum or platinum alloy is formed on it by various film forming methods such as vapor deposition and sputtering. used. These substrates can be of various shapes, such as a tape shape or a normal substrate shape.

When using the above platinum alloy, it is preferable to use one containing 90% by weight or more of platinum, and when using a substrate with a layer of platinum or platinum alloy formed on the surface, the content varies depending on the platinum content. , is preferably approximately lOμ or more.

The compound superconducting conductor of the present invention is produced, for example, as follows.

First, the oxide superconductor is heated above its melting point to melt it, and this melt is applied onto the platinum or platinum alloy layer of the substrate. Alternatively, the powder of the oxide superconductor is applied onto the platinum or platinum alloy layer of the substrate, and then heated to a temperature higher than the melting point of the oxide superconductor to melt it. Application of the heated and melted oxide superconductor is carried out by immersing the substrate in the melt, or by applying the melt from a nozzle provided at the bottom of the heated crucible.

The starting material for this oxide superconductor may be one that has been pre-crystallized by mixing the constituent elements or compounds at a predetermined composition ratio and calcining the mixture at a predetermined temperature, or the above-mentioned oxide superconductor. Single constituent elements or mixtures of compounds are used. When using this mixture as a starting material, it is basically mixed so that it has a stoichiometric composition, but even if the composition deviates from this stoichiometric ratio, the crystals of the oxide superconductor will still form. is generated. Further, a large amount of components having low vapor pressure may be blended in advance.

The oxide superconductor in a state above its melting point on the platinum or platinum alloy layer reacts with the platinum to form a dense intermediate reaction layer that is firmly bonded to the substrate.

Thereafter, the molten oxide superconductor is solidified and crystallized to form an oxide superconductor layer.

This crystallization of the oxide superconductor is preferably carried out in an atmosphere that can sufficiently supply oxygen.

The oxide superconductor coated on the substrate may be melted after the same surface as the substrate is coated with a material having a platinum or platinum alloy layer, or the oxide superconductor coated on the substrate may be melted. The solidification of the molten material of the physical superconductor may be carried out after it is coated with the same material as the substrate. Further, after crystallizing the oxide superconductor, depending on the type of the oxide superconductor, heat treatment is performed in an oxygen atmosphere as necessary to introduce oxygen.

(Function) In the present invention, the oxide superconductor is caused to experience a molten state on the platinum or platinum alloy layer of the base. At temperatures above the melting point of the oxide superconductor, the reaction between the oxide superconductor and platinum proceeds rapidly, resulting in a reaction involving a compound of the constituent elements of the oxide superconductor and platinum between the oxide superconductor and the substrate. A layer is formed. This reaction layer is dense and strongly bonds to the substrate, and also firmly bonds to the oxide superconductor layer after solidification.

In this manner, the compound superconducting conductor of the present invention has a substrate and an oxide superconducting layer firmly bonded to each other by the intermediate reaction layer. Therefore, even when external stress such as bending is applied, the occurrence of peeling between the substrate and the oxide superconductor layer, cracking of the oxide superconductor layer, etc. is suppressed, and the resulting deterioration of superconducting properties such as critical current density. is prevented.

(Example) Next, embodiments of the invention will be described.

Example 1 Bi2O3, SrCO3, CaCO3, CuO as starting materials for B1-8r-Ca-Cu-0 based oxide superconductor
The molar ratio of cations is Bi:Sr:Ca:C.
After weighing a predetermined amount so that the ratio of u-2:2:2:3 was sufficiently mixed in a ball mill, this mixed powder was placed in an aluminum crucible and temporarily heated in air at 800°C for 8 hours. It was baked and subjected to solid phase reaction. Next, this calcined product was thoroughly ground and mixed again in a ball mill to reach a critical temperature of 107K.
A B i -8r-Ca-Cu-0 based oxide superconductor powder was obtained. The cation ratio of this powder is Bi:Sr
:Ca:Cu-2:2:2:3.

Next, the oxide superconductor powder was placed in a platinum crucible and heated to a temperature of about 1000° C. to melt it.

Then, in this melt, 1On+mX 50cu+X
After a 51 mm platinum substrate was immersed for about 1 hour, the platinum substrate was pulled up and a molten Bi-based oxide superconductor was uniformly deposited on the platinum substrate.

Thereafter, the melt of the Bi-based oxide superconductor deposited on the platinum substrate was cooled in an oxygen-containing atmosphere, and the melt was solidified to form an oxide superconductor layer.

As shown in FIG. 1, the obtained superconducting conductor has a thin and uniform intermediate reaction layer 3 between the platinum substrate 1 and the BI-based oxide superconductor layer 2. B by 3
The i-based oxide superconductor layer 2 was firmly bonded to the platinum substrate 1. The existence of this intermediate reaction layer 3 was clearly confirmed by enlarged observation of the cross section.

In addition, when the critical current density of the obtained superconducting conductor was measured, it was found to be 77K, O
100 A/c at T, and 100 OA/c of a superconducting conductor by a conventional reaction method using a silver sheath.
Although it was only slightly improved compared to d, the critical current density value under bending stress was significantly improved.

The results are shown in FIG. Figure 2 shows the values of critical current densities dpj and dpj using the superconducting conductor of this example and a conventional superconducting conductor with a silver sheath, while applying bending stress to each.
2 is a graph showing the determined results with bending strain plotted on the horizontal axis.

As is clear from the figure, the superconducting conductor of this example is
It can be seen that the critical current density decreases only slightly with an increase in bending strain, whereas in the conventional superconducting conductor with a silver sheath, the critical current density decreases rapidly with an increase in bending strain.

Example 2 The procedure of Example 1 is repeated, except that a composite substrate 13 in which a platinum layer 12 is formed by sputtering on a copper substrate material 11 is used, as shown in FIG. 2, in place of the platinum substrate in Example 1.
A Bi-based oxide superconductor layer 14 was formed under the same conditions as described above.

Also in the superconducting conductor of this example, the platinum layer 12 and B1
It was confirmed that an intermediate reaction layer 15 was formed between the oxide superconductor layer 14 and the oxide superconductor layer 14 . Note that the thickness of the platinum layer 12 was 5 μm.

In the superconducting conductor of this example as well, the composite substrate 13 and the Bi-based oxide superconducting layer 14 were firmly joined by the intermediate reaction layer 15. Further, regarding the change in critical current density with respect to external stress, as in Example 1, the critical current density value decreased only slightly with respect to an increase in bending strain.

Example 3 B produced in Example 1 on the platinum substrate used in Example 1
The i-type oxide superconductor powder was uniformly applied and heated from below the platinum substrate to a temperature above its melting point to melt the oxide superconductor powder. Thereafter, the melt of the Bi-based oxide superconductor was solidified in an oxygen-containing atmosphere to form an oxide superconductor layer.

The superconducting conductor obtained in this way also showed a significant improvement in the reduction in critical current density with respect to bending stress, as in Example 1.

Example 4 Next, manufacturing of a long superconducting conductor will be explained. FIG. 4 is a diagram showing a purchasing example of an apparatus for continuously forming an oxide superconductor layer on a long tape-shaped substrate. In the figure, 21 is a high temperature bath, and the oxide superconductor 22 is melted in this high temperature bath 21 and held in that state. Then, a tape-shaped substrate 23 made of platinum or a platinum alloy, or a tape-shaped substrate 23 with a platinum or platinum alloy layer formed on the surface, is
A molten layer 25 of the Bi-based oxide superconductor is formed on the surface of the tape-shaped substrate 23 by passing it through the molten oxide superconductor 22 in the high-temperature bath 21 at a predetermined speed using the guide roller 24. .

After that, a long superconducting conductor is formed by continuously solidifying the melt layer 25 of the other type of oxide superconductor,
This long superconducting conductor also has a tape-like substrate and an oxide superconducting layer firmly joined by an intermediate reaction layer, as in each of the above-mentioned examples, and more stable superconducting conductors of various types can be obtained.

In each of the above embodiments, a Bi-based oxide superconductor was explained as an example, but similar effects can be obtained in a defective perovskite-type oxide superconductor represented by a V-based oxide superconductor or a Tl-based oxide superconductor. You can expect it.

[Effects of the Invention] As explained above, according to the present invention, a compound superconducting conductor in which a substrate and an oxide superconductor layer are firmly joined by an intermediate reaction layer can be obtained. Therefore, deterioration of superconducting properties such as critical current density when external stress is applied can be suppressed, making it possible to provide a more stable compound superconducting conductor.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the structure of a compound superconducting conductor according to an embodiment of the present invention, and Figure m2 is a bending strain of critical current density of a compound superconducting conductor according to an embodiment of the present invention and a conventional compound superconducting conductor with a silver sheath. A graph showing the dependence; FIG. 3 is a cross-sectional view showing the structure of a compound superconducting conductor according to another embodiment of the present invention;
FIG. 4 is a diagram showing an example of the configuration of an apparatus for continuously manufacturing elongated compound superconducting conductors. 1... Platinum substrate, 2.14... Oxide superconductor layer, 3.15... Intermediate reaction layer, 11.
... Substrate material made of copper, 12 ... Platinum layer, 13 ... Composite substrate, 23 ... Tape-shaped substrate, 25 ... Oxidation Molten layer of physical superconductor. Applicant: Toshiba Corporation

Claims (2)

[Claims] (1) A substrate having a platinum or platinum alloy layer on at least the surface, and an intermediate reaction layer containing a compound of platinum and a constituent element of an oxide superconductor formed on the platinum or platinum alloy layer of the substrate. A compound superconducting conductor comprising an oxide superconducting layer. (2) After heating and melting an oxide superconductor or a mixture that becomes an oxide superconductor by heating, this melt is applied onto a substrate having a platinum or platinum alloy layer on at least the surface, or the oxide superconductor or After applying a mixture that becomes an oxide superconductor by heating onto the platinum or platinum alloy layer of the substrate, the oxide superconductor or the mixture that becomes an oxide superconductor by heating is heated and melted, and then the melt is melted. A method for producing a compound superconductor, which comprises crystallizing to form an oxide superconductor layer.