JPH04138621A - Superconducting member - Google Patents

Abstract

PURPOSE:To eliminate anisotropy of a critical current or the like relating to a magnetic field by orienting a crystal axis of the longest lattice constant of all so as to be almost vertical relating to a base body, and further providing a part with a different direction of the crystal axis. CONSTITUTION:A tape-shaped base body 11, in which rolling work is applied in a fixed direction relating to a silver material, is recrystalized by heat treatment. Next, an orientation surface by a (100) surface of this silver tape is set up in a filming device so as to be opposed to a spatter source, and yttrium, barium, copper are respectively spattered and continuously accumulated on the orientation surface of the tape. Then, a plurality of sheets of this unit wire rod 13 are piled and pressed to prepare a plurality of units 14. Successively, this plurality of these units 14a, 14b, 14c, 14d are piled together so that molded units 12 of the adjacent units 14 are vertical to each other and further pressed. In this way, extreme reduction of a critical current can be prevented by suppressing anisotropy relating to a magnetic field of the critical current.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a superconducting member.

(Prior art) Oxide-based superconductors have attracted attention since it was announced in 2019 that Ba-La-Cu-0 layered perovskite oxides had a high critical temperature higher than IK. Research is being actively conducted to collect and search for new materials.

Among them, defective perovskite-type oxide superconductors represented by the Y-Ba-Cu-0 system and B1-9r-Ca-Cu-0
The oxide superconductors of the T l-Ba-Ca-Cu-0 system have important industrial value because they can use inexpensive liquid nitrogen as a refrigerant instead of expensive liquid helium. There is.

When considering the application of such oxide superconductors to the energy field, it is first necessary to make them into wires. Therefore, attempts have been made to produce wires from oxide superconductors using various methods.

Methods for producing superconducting wire using oxide superconductors include: (^) A method of sealing an oxide superconductor in a metal tube and drawing it into a wire.

(B) A method in which oxide superconductor powder and organic binder are mixed and extruded from a nozzle to form a wire rod.

(C) A method of forming an oxide superconductor layer on a metal tape by thermal spraying or various film forming methods, and forming it into a wire.

etc. are known.

The critical current density of superconducting wires using these oxide superconductors tends to gradually improve, and among the above methods, method (C) is particularly easy to obtain an oxide superconductor layer with excellent orientation. , is attracting attention because it is expected to improve superconducting properties such as critical current density. However, in order to put it into practical use as a superconducting wire, a sufficiently large critical current is required, so no matter which method is used to produce it, it is necessary to bundle and integrate multiple wires for use.

By the way, in general, in oxide superconductors, when a magnetic field is applied in the direction of the crystal axis (C axis) with the longest lattice constant, the critical current decreases significantly, so it is difficult to form a film with the C axis on the tape-shaped substrate. If the superconductor layer is formed perpendicular to the plane, the critical current will drop significantly with respect to the magnetic field in that direction.

When such wires are used in a bundle, if the crystal axes of the oxide superconductor layer 2 on the substrate 1 are aligned in one direction as shown in FIG. It becomes extremely weak against the magnetic field and has anisotropy.

On the other hand, if the oxide superconductor layer is formed without C-axis orientation on the substrate, the above-mentioned problem does not occur, but the critical current per superconducting wire becomes small, resulting in anisotropy with respect to the magnetic field. However, it becomes difficult to flow a sufficient current for practical purposes.

(Problems to be Solved by the Invention) As mentioned above, in order to improve superconducting properties such as critical current, when wires having C-axis oriented oxide superconductor layers are bundled in the same direction, However, the problem is that anisotropy of the critical current occurs.

The present invention has been made to address the problems of the prior art, and aims to provide a superconducting member that eliminates anisotropy in superconducting properties such as critical current with respect to a magnetic field.

[Structure of the Invention] (Means for Solving the Problems) In other words, the superconducting member of the present invention is a superconducting member formed by integrating a plurality of unit members in which a substance exhibiting superconducting transition is composited with a substrate, in which the plurality of units A substance exhibiting superconducting transition in the member is oriented such that the crystal axis having the longest lattice constant among the crystal axes of the substance is substantially perpendicular to the substrate, and the crystal axis has a portion in which the direction of the crystal axis differs. It is characterized in that the plurality of unit members are integrated.

Substances exhibiting superconducting transition in the present invention include, for example, rare-earth element-containing perovskite-type oxide superconductors, B1-8r-Ca-Cu-0-based oxide superconductors, and Tl
-Ba-Ca-Cu-0-based oxide superconductors are exemplified.

The oxide superconductor containing a rare earth element and having a perovskite structure may be one that can realize a superconducting state, for example, RE M2 Cu30 Fu system (RE is Y, La, Sc, Nd, Ss,
Eu, Gd.

At least one element selected from rare earth elements such as Dy, Ho, Er, TII, Yb, Lu, etc.
is at least one element selected from Ba and 5rSCa, δ represents an oxygen defect and is usually a number of 1 or less, and a part of Cu is TrSV, Crs, Fe%Co, Ni, Z
Examples include oxides of (substitutable with n, etc.). Note that rare earth elements are defined in a broad sense and include Sc, Y, and La elements.

In addition, the B1-3r-Ca-Cu-0-based oxide superconductor has the chemical formula: Bi25r2Ca2Cu30x
---(1): 812 (Sr, Ca)3Cu20
x -------(II) (In the formula, a part of Bi can be replaced with pb etc.), etc., and T
The l-Ba-Ca-Cu-0 based oxide superconductor has the chemical formula: Tl2 Ba2Ca2Cu30x -
-----(I[I): T12(Ba, Ca)3Cu
There are some expressions such as 20x ・=−・−(IV).

Examples of the unit member used in the superconducting member of the present invention include those in the form shown below, in which the crystal axis with the longest lattice constant among the crystal axes of the superconductor is approximately perpendicular to the substrate. Use one oriented so that

(a) A composite material in which superconductor layers are laminated on a tape-shaped or wire-shaped substrate.

(b) A compound made by filling a tubular base with a superconductor.

The substrate in (a) above is preferably one in which at least the surface on which the superconductor layer is formed is made of silver,
The entire substrate may be made of silver, or it is also possible to use a material in which a silver layer is formed on a core material made of iron, nickel, chromium, or an alloy thereof, which is difficult to form a solid solution with silver.

In addition, the surface of the above substrate on which the superconductor layer is formed is made of silver.
(100) crystal plane or (110) crystal plane orientation plane,
Alternatively, it is preferable to use a mixture of these orientation surfaces. In this way, the surface on which the superconductor layer will be formed is coated with silver (
For example, in the case of an oxide superconductor, C It is possible to obtain an axially oriented superconductor layer, and is particularly suitable for oriented a superconductor layer in the (100) crystal plane.

The degree of orientation of these silver crystal planes is preferably 60% or more parallel to the formation plane of the superconductor layer, with the (100) crystal plane, the (110) crystal plane, or a mixture of these. In particular, it is preferable to orient 80% or more of the (100) crystal plane of silver.

Such a (+00) crystal plane or (110) crystal plane of silver can be obtained by rolling silver in the direction of the oriented plane and aligning the crystal orientation by a slip plane. Since the (110) crystal planes obtained by rolling are likely to be aligned, it is preferable to recrystallize by heat treatment thereafter. This recrystallization coarsens the silver crystal grains and improves the degree of orientation of the (100) crystal plane, making it easier to orient the crystal orientation of the superconductor.

The unit member in the present invention using the above-mentioned substrate can be produced by physical vapor deposition such as sputtering, reactive vapor deposition, laser vapor deposition, chemical vapor deposition such as CVD, or MO.
It can be obtained by forming a superconductor layer on a substrate using various thin film forming methods such as CVD method. Further, the superconductor layer may be formed by a thick film method such as a doctor blade method, and in this case, after coating, the superconductor layer is
Sintering is carried out at a temperature of about 1000°C to 1000°C. Note that the sintered materials may be integrated, or they may be integrated first and then sintered.

The unit member shown in (b) above can be obtained by filling a tubular base made of the same material with superconductor powder and subjecting it to swaging, rolling, wire drawing, etc. The superconductor in such a unit member can be oriented by applying force from one direction during rolling or by applying a magnetic field.

The superconducting member of the present invention is such that when a plurality of unit members as described above are integrated, each unit member has a portion in which the oriented crystal axes of the unit members differ in direction. When uniting multiple unit members with their axes aligned, and then bundling them together, it is difficult to integrate them so that they are perpendicular to the orientation of the crystal axes. An example is one in which the direction is integrated.

(Function) In the superconducting member of the present invention, a plurality of unit members are integrated so that the directions of the oriented crystal axes of the superconductors in the unit members are different, so that a magnetic field is applied from a certain direction. When a magnetic field is applied, the superconducting properties of unit members whose crystal axes are oriented in the direction of the magnetic field deteriorate;
In other unit parts, the deterioration of superconducting properties is small, so
The current mainly flows there, and the critical current does not become extremely low.

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

Example 1 First, an Ag material was rolled in a certain direction and drawn to produce a long tape-like substrate with a width of 10I and a thickness of 1II11. When the crystal orientation of the main surface (pressure application surface) of the Ag tape thus obtained was analyzed by X-ray diffraction, it was found that the (110) plane was oriented almost parallel to the longitudinal direction of the main surface. . Next, this A
The g tape was subjected to heat treatment for recrystallization at 700° C. for 60 minutes. When the crystal orientation of the same plane after the heat treatment was examined by X-ray diffraction, it was found that the (100) plane was oriented, and the degree of orientation was 80%, and the rest were (110) planes.

Next, the Ag tape is installed in a film forming apparatus so that the (100) oriented surface faces the sputtering source.
YSBaXCu was sputtered onto each of the Ag tapes, and after controlling the film thickness to 1 μI using a film thickness monitor, a YBa2Cu30□-6 film was continuously deposited on the oriented surface of the Ag tape to produce a unit wire.

Analysis of the crystal orientation of the thus obtained YBa2Cu307-,l film by X-ray diffraction revealed that the C axis of the oxide superconductor was oriented perpendicular to the (100) plane of the Ag tape. confirmed. In addition, the superconducting property has a critical temperature of 85K, and the critical current density at 77K is IX
It was 10' A/c.

Next, as shown in FIG. 1, YBa is placed on the Ag tape 11.
Approximately 10 to 1000 unit wire rods 13 formed by orienting the 2Cu30□-6 film 12 are stacked, and
A plurality of units 14 were produced by pressing at a pressure of kg/c-. After this, the plurality of units 1
4a, 14b..., YBa of the adjacent unit 14
The 2Cu307-6 films 12 were stacked perpendicularly to each other and further pressed to obtain the desired superconducting wire.

The critical current of the wire produced in this way was 100 OA or more in the absence of a magnetic field. Furthermore, when a magnetic field was applied, almost no anisotropy was observed no matter which direction it was applied, and the degree of decrease in the critical current was small (a critical current of 1008 or more was obtained even in a magnetic field of 10 T).

In addition, in the above-mentioned superconducting wire, when a magnetic field is applied in the X direction, the units 14a oriented in the C-axis or the X-axis direction,
14d has lower superconducting properties, but other units 1
4b and 14C have little or no deterioration in superconducting properties, so current mainly flows through them, and the critical current does not become extremely low. The same applies to the two directions.

Example 2 A YBa2Cu30□6 film with a thickness of 1 μm was formed by vapor deposition on the Ag tape used in Example 1 to produce a unit wire, and this was integrated in the same manner as in Example 1 to obtain a superconducting wire. Ta.

Similar to Example 1, this superconducting wire also showed no anisotropy in the critical current with respect to the magnetic field, and the degree of decrease in the critical current when a magnetic field was applied was small. A larger critical current was obtained because at least a portion of the deposited particles were clustered or ionized during the formation of the superconductor film. Therefore, it has become possible to make the superconducting wire necessary to pass the same current even thinner.

Example 3 On the Ag tape used in Example 1, a film containing Y and Ba5Cu in a composition ratio of approximately 1:2:3 was coated to a thickness of 20 μD by a doctor blade method.

Next, this was sintered to produce a unit wire rod, which was integrated in the same manner as in Example 1.

With this method, a thick film can be easily obtained, so the number of layers to be stacked can be small. However, since the critical current density is small compared to others, the effect may not be so great.

Example 4 A Cu tape with a width of 1 mm and a thickness of 1.
After forming a film with a thickness of about 11 mm, YBa2Cu307 is formed by sputtering, vapor deposition, doctor blade method, etc.
-J film was formed. It was integrated in the same manner as in Example 1.

In the case of the above composite tape, compared to Ag tape,
The crystallinity and orientation of the superconductor formed on it are slightly inferior, so the critical current is small, but the price of the substrate itself is low, so it can be used depending on the purpose.

Example 5 As shown in FIG. 2, a plurality of unit wire rods 13 produced in the same manner as in Examples 1 to 4 were stacked and pressed, and processed into a trapezoid to produce a unit 15. This unit 15 may be manufactured by forming films on tapes having slightly different widths, overlapping them, and pressing them. Next, these units 15, 15... were bundled and integrated so that the cross section had a polygonal shape.

By adopting such a structure, the anisotropy of the critical current with respect to the magnetic field is further eliminated. Also, if the polygon has many corners, the anisotropy will be improved.

〔Effect of the invention〕

As explained above, according to the superconducting member of the present invention, since the C-axes of the oriented superconductor films are integrated so that they are not aligned in one direction, the superconducting member has suppressed anisotropy with respect to the magnetic field of the critical current. It becomes possible to provide

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a superconducting member according to one embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a superconducting member according to another embodiment of the present invention, and FIG. 3 is a diagram showing the configuration of a superconducting member according to another embodiment of the present invention. It is a figure showing the composition of a member. 11... Tape-shaped substrate, 12... Oxide superconductor layer, 13... Unit wire, 14.15.
...-Unit.

Claims (1)

[Claims] In a superconducting member formed by integrating a plurality of unit members in which a substance exhibiting superconducting transition is composited with a substrate, the substance exhibiting superconducting transition in the plurality of unit members is a crystal with the longest lattice constant among the crystal axes of the substance. A superconducting member, characterized in that the plurality of unit members are oriented so that their axes are substantially perpendicular to the base, and are integrated so that the crystal axes have different directions.