JPH0261910A - Superconducting material wire and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a superconductor wire with a small diameter and high critical current density by attaining a wire of an oxide-type superconductive material with metal or with another oxide and making the metal having a plurality of grooves parallel to the direction of the wire axis. CONSTITUTION:Silver-made wires 2 are placed on a silver thin plate 1' with a prescribed thickness, while keeping a prescribed distance each other and having a peeling agent 3 between each wire and the sheet and the resulting set is rolled with a roller 4 so as to obtain a plate 1'' in which the wires 2 are buried. The wires 2 are then peeled to give a substrate 1 having a lot of grooves. To manufacture a thin film of a superconductor, a crystal 6 of RxByCux+y+deltaOz with a prescribed thickness is formed on the groove-bearing substrate 1 by sputtering where R stands for Y, Ru, Gd, Tb, Dy, Pr, or Yb and B stands for Sr or Ba. The critical current of a superconductor wire of the RxByCux+y+deltaOz can thus be improved while its transition temperature (Tc) is maintained as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a superconducting wire such as a coil for a large electromagnet and a power transmission line made of an oxide superconducting material, and a method for manufacturing the same.

(Prior art) Oxide superconducting materials (for example, YBazCusOt-y) with the composition RX B ycux * y + J Oz are known to have a high superconducting transition temperature (Tc), and attempts have been made to make them into wires. being done. However, the wire obtained by the conventional method of packing powder of this substance into a copper or silver pipe and drawing it has a low critical current density (Jc) of only 1000 A/c++'', making it difficult to put it to practical use in the energy field. In addition, to improve magnetic and thermal stability, it is necessary to make the wire thinner to a diameter of several micrometers, but there is a limit to how thin the wire can be made due to the difficult processability characteristic of oxides.

It is known that oxide superconducting materials have anisotropy in the flow of electrons, and in perovskite oxide superconducting materials, it is difficult for current to flow in the C-axis direction of the crystal, and in the direction perpendicular to the C-axis. Current flows easily.

This has been confirmed by experiments using a single crystal of YBazCusO+,y (Japanese
Journal of Applied Physics
, νo1.26 (1987), L726).

Therefore, if a wire can be created in which the C axis of the perovskite oxide superconductor is aligned perpendicular to the longitudinal direction of the wire, its critical current density should increase. but,
In the method of filling a sheath (pipe) of copper or the like with sintered oxide particles and drawing it, the crystal orientation of the superconducting material becomes random, and it is not possible to obtain a wire with uniform crystal orientation as described above.

On the other hand, it is known that a crystalline film of an oxide-based superconducting material can be grown on a ceramic substrate by sputtering vapor deposition so that the C-axis is preferentially oriented perpendicular to the substrate surface (Japanese Journal of Appl.
ied Physics, Vol. 26 (1987),
L1221), the applicant has previously filed a patent application for an improved method for manufacturing a superconducting coating material and a method for manufacturing a wire using this vapor deposition method. (Special application 1986
-327949, Japanese Patent Application No. 63-6169) (Problems to be Solved by the Invention) The present invention provides a superconducting wire material with a high critical current density and a small wire diameter, and a superconducting material coating material using a sputtering method etc. To provide a new method for manufacturing the above-mentioned wire rod, which combines the manufacturing method of t7 with rolling and other wire rod manufacturing methods;
With the goal.

(Means for Solving the Problems) The gist of the present invention is the following superconducting material wire and method for manufacturing the same.

■ A wire consisting of an oxide-based superconducting substance and a metal, or an oxide-based superconducting substance, another oxide, and a metal, characterized in that the metal has a plurality of grooves parallel to the axial direction of the wire. Superconducting material wire.

■ A plurality of grooves are formed on the surface of a metal substrate or a metal substrate coated with an oxide other than an oxide-based superconducting material, so that when it is later processed into a wire, it becomes parallel to the axial direction of the metal substrate. A method for manufacturing a superconducting material wire, which comprises forming an oxide-based superconducting material layer on a metal substrate coated with an oxide, and winding the obtained plate-like material into a wire.

(2) The method for manufacturing a superconducting material wire according to (2) above, which comprises winding it into a wire and then further rolling or drawing or both.

FIG. 1 and FIG. 2 schematically show the manufacturing process of the superconducting wire of the present invention. The method of the present invention will be explained step by step with reference to this figure.

(2) Step of forming grooves on a metal substrate (Fig. 1) Various methods can be used to form a plurality of grooves on a metal substrate, such as machining such as cutting or rolling with a grooved roll. What is shown in FIG. 1 is an example of a groove forming method.

First, on a thin silver plate 1' having a thickness of, for example, 200 to 500 .mu.m, silver wire rods 2 (width and thickness of about 100 .mu.m) are arranged at predetermined intervals via a release agent 3. If this state is rolled by the roll 4, a plate 1″' with the wire rod 2 pushed into the substrate will be produced.After that, if the wire rod 2 is peeled off,
A substrate 1 in which a large number of grooves are formed is obtained. According to this method, it is easy to manufacture thin substrates that are difficult to groove by cutting or the like.

Note that the silver wire used in the above example is because if a wire with the same deformation resistance as the substrate is used, the ratio of the depth of the groove created in the first rolling to the substrate thickness will reduce the thickness of the substrate. This is because it will be maintained no matter what. However, it is not always necessary to use wires made of the same material as the substrate.

When the grooved substrate thus obtained is bent along the groove in a later process, it bends preferentially at the thin grooved part.
Since the thick portion is difficult to bend, the layer of oxide-based superconducting material formed in the thick portion is less likely to peel off.

■ Process of creating a thin film-like superconducting coating layer (Figure 2) ■
For example, RxBvCuw+y* is deposited on the metal substrate 1 obtained by sputtering under the following conditions.
Attach SOz crystal 6 (about 2 to 10 um thick). In addition, in this composition formula, R is Y, Eu, Gd,
It represents either Tb, DV, Er, or Yb, and B represents Sr or Ba.

The substrate may be a thin metal plate with an oxide layer 5 such as MgO or 5rTiOs as shown in FIG. 2 (Ao). If such an oxide layer is provided, even if a metal that easily reacts with oxide-based superconducting materials is used as the metal of the substrate, such as copper that easily reacts with YBaxCusOt-1, the oxide layer 5 will prevent the reaction. In this case, the oxide I
I5 is preferably formed by sputtering, vacuum deposition, or the like on the metal substrate on which the grooves have been previously formed.

Examples of sputtering conditions for forming a layer of oxide superconducting material on the substrate as described above are as follows.

Method: 28i sputtering Voltage: 1.5 to ν Atmosphere: Ar gas partial pressure 0.03 to 0.05 Torr.

+ Oxygen gas partial pressure 0.03 to 0.05 Torr.

Cathode (e.g. RJavCLlx+yesOz sintered body)
Distance between and anode (substrate): 5 cm Substrate temperature: 500°C or higher when forming YBazCusOt-y, or 450°C or higher when forming YSrtCus()+-y. The C-axis of the crystal 6 of the superconducting material RXByCux+y-JOz shown by Ao is grown preferentially in the direction perpendicular to the substrate surface.

■ Linear winding process A plate-shaped material with a superconducting oxide film formed on the surface as shown in Figure 2 (A) or (Ao) is wound in the axial direction as shown in Figure 2 (B). Roll it to make a wire. When rolling into a tape-shaped product, from (B) to (
Form it into a flat plate as in C), or (A), (
Make the shape (C) directly from A'). Since a thin metal substrate such as silver is used and a large number of grooves are formed in this substrate as described above, it can be easily made into a wire without peeling off the oxide layer or disordering the crystal orientation. In addition, in the present invention, "linear" includes the above-mentioned flat plate shape and tape shape.
We will refer to them collectively as

■Rolling and drawing process Figures 2 (B) and (C) can be used as superconducting wires as they are, but they are usually further rolled and/or drawn to make thin wires. In order to put superconducting wire into practical use, the wire must have a diameter of several micrometers in order to avoid destruction of the superconducting state due to magnetic flux movement when current is turned on and off.In general, oxide-based superconducting materials cannot be used with other ceramics. Similarly, it has poor processability and is extremely difficult to thin wire. However, according to the method of the present invention, a thin wire with a diameter of several μm or a tape with a thickness of several μm can be obtained relatively easily.

In the conventional method, metal tubes are filled with oxide superconductor powder and then rolled or drawn, but not only is it time-consuming to fill the powder, but there are limits to how small the tube diameter can be. be. In contrast, in the method of the present invention,
Since the oxide superconductor is coated on an extremely thin metal plate of, for example, 10 μm, it is easy to wind, roll, and draw the metal plate.

In the thus obtained wire of the present invention, as can be seen from FIG. 2(B), the C-axes of the crystals of the superconducting substance are aligned perpendicularly to the longitudinal direction of the wire. In other words,
The longitudinal direction of the wire is the direction in which current flows easily.

During rolling or drawing, the crystal grains of the oxide superconductor are broken into small crystal grains, but the preferential orientation of the C-axis is maintained even in this case. Therefore, this wire exhibits a significantly higher critical current density than conventional wires of superconducting materials in which the crystal orientation is random.

In addition, the cross section of the superconducting wire of the present invention has a laminated structure of a thin metal plate and a thin film of superconducting material, so even if the superconducting state is broken in a part and heat is generated, the heat can easily pass through the thin metal plate. released.

(Example 1) Silver wires with a square cross section of 100 μm on each side were arranged at 500 μ-intervals on a 500 μ-thick silver plate with a stripping agent mainly composed of mica and glass. Cold rolled to After that, remove the pressed silver wire and create a groove with a depth of about 20μ+* and a width of about 100 pm and a width of 500 pm.
A substrate formed with intervals was obtained. On this substrate, YBa with a thickness of 10 μm was deposited by DC sputtering under the following conditions.
A plate-like material was obtained by depositing a tCusOg-y film.

Suba gong Atmosphere: Argon partial pressure 0.05 Torr.

+Oxygen partial pressure 0.05 Torr.

Target (cathode): YBazCLIsOt-
y sintered body or YSrlCu30t-y sintered body Discharge voltage: 1.5 KV Anode-cathode distance: 5 cm Substrate temperature: The material obtained by heating to 600'' was shaped into a flat plate with a thickness (t) as shown in Figure 3.
) 1m+m, width (w) 5+wm, length (jri 100m
- rolled into 10 layers and cold rolled to a thickness of 0.
3++ m tape and its superconducting transition temperature (Te
) was investigated. The results are shown in FIG.

(Example 2) A copper wire with a square cross section of 100 μm on each side was coated with 500 μm of copper wire on a 500 g thick copper plate using the above-mentioned stripping agent.
They were arranged at m intervals and cold rolled to a thickness of 100 μm. Thereafter, the pressed copper wire was removed to obtain a substrate in which grooves having a depth of approximately 20 μm and a width of approximately 100 μm were formed at intervals of 500 μm. A 10 μι MgO film was formed on this substrate by sputtering, and then a YB film was formed as in Example 1.
atCu+0y-y or YSrzCu30ty was vapor-deposited to a thickness of 10 m, and a tape with a thickness of 0.31 was obtained from the plate-shaped material under the same conditions as in Example 1. The measurement results of the superconducting transition temperature (Tc) are shown in FIG.

(Comparative example) Similar to the conventional manufacturing method, YBazCII+ with an outer diameter of 6 cm
The sintered bodies of 0, -7 and YSrtCusOq-1 were each packed into a silver vibrator with an outer diameter of 10 mm and an inner diameter of 6 cm, and cold wire drawing was performed to produce a wire rod with an outer diameter of 31111 mm.

The critical current density at 77 K was measured for the wire thus obtained and the wire obtained in Example 1.2. The results are shown in Table 1.

Table 1 (Effects of the Invention) As is clear from the results of the examples, the superconducting material wire of the present invention has RX B vcux+y*so Z original Tc
The critical current density is much higher than that by traditional manufacturing methods.

The present invention is Rx B yCu□4. Needless to say, the present invention can be applied to wires made of oxide superconducting materials other than the δ0□-based material, and promotes the practical use of all kinds of oxide superconducting materials.

[Brief explanation of the drawing]

1 and 2 are diagrams schematically showing the manufacturing process of a superconducting material wire of the present invention, FIG. 3 is a schematic perspective view of a wire manufactured in an example of the present invention, and FIGS. 4 and 5 The figure is a diagram showing measurement results of superconducting transition temperatures of wires obtained in Examples of the present invention.

Claims (3)

[Claims] (1) A wire consisting of an oxide-based superconducting substance and a metal, or an oxide-based superconducting substance, another oxide, and a metal, characterized in that the metal has a plurality of grooves parallel to the axial direction of the wire. superconducting material wire. (2) A plurality of grooves are formed on the surface of a metal substrate or a metal substrate coated with an oxide other than an oxide-based superconducting material, and the grooves are parallel to the axial direction of the wire when it is later processed into a wire. A method for producing a superconducting material wire, which comprises forming an oxide-based superconducting material layer on a substrate or a metal substrate coated with an oxide, and winding the obtained plate-like material into a wire. (3) The method for manufacturing a superconducting material wire according to claim 2, which further comprises rolling or drawing, or both, after winding it into a wire.