JPS63264814A - Plexible superconductive material - Google Patents

Abstract

PURPOSE:To make a superconductive material, which is high in its superconductive critical temperature Tc, usable as a wire with high stability of its superconductive characteristic and a large degree of freedom in its size by using a specific composite oxide thin film and a flexible substrate which supports this thin film. CONSTITUTION:There are used the following matters: a composite oxide thin film, which is 1 mum or less in thickness and indicated in a formula (Ax-1,Bx)CyDz, and a flexible substrate, which supports this thin film. In this formula, A is one species selected from group IIa, IIIa elements in a periodic table, B is one species selected from group IIa, IIIa elements in the periodic table and includes the same elements as contained in A, C is one species selected from group Ib, IIb, IIIb, VIIIa elements in the periodic table, D is one species selected from the following elements; O, B(boron), C(carbon), N, F, S, x is an atomic ratio of B to A+B and defined in 0.1<=x<=0.9, y and z are atomic ratios defined in 0.4<=y<=3.0 and 1<=z<=5 respectively when (Ax-1Bx) is one.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to superconducting materials. More specifically, the present invention relates to a novel structure of a superconducting material that can effectively utilize a superconducting material with a high superconducting critical temperature.

Conventional technology Under superconducting phenomena, materials exhibit complete diamagnetic properties, and no potential difference appears even though a finite steady-state current flows inside them. Therefore, various applications of superconductors as transmission media with no power loss have been proposed.

That is, its application fields include power fields such as MHD generation, power transmission, and power storage, power fields such as magnetic levitation trains and electromagnetic propulsion ships, and NMR1π as an ultra-sensitive sensor for magnetic fields, microwave ζ radiation, etc. There are many fields that can be mentioned, such as meson therapy, measurement fields such as high-energy physics experimental equipment, etc.

Furthermore, in the field of electronics, typified by Josephson devices, this technology is expected to not only reduce power consumption but also realize devices that operate at extremely high speeds.

By the way, superconductivity was once a phenomenon observed only at extremely low temperatures. That is, Nb, which is said to have the highest superconducting critical temperature Tc among conventional superconducting materials,
Even in Ge, an extremely low temperature of 23.2 K was considered to be the limit of superconducting critical temperature for a long time.

Therefore, conventionally, in order to realize the superconducting phenomenon, superconducting materials have been cooled to below Tc using liquid helium with a boiling point of 4.2. However, the use of liquid helium imposes an extremely large technical burden and cost burden due to cooling equipment including liquefaction equipment, which has hindered the practical application of superconducting technology.

However, in recent years, it has been reported that sintered bodies containing oxides of LA group elements or ■A group elements can become superconductors at extremely high Tc, and the practical application of superconducting technology using non-low-temperature superconductors has been delayed. is about to be promoted. In already reported examples, CLa, Ba) zc, which is thought to have a crystal structure similar to perovskite oxides,
u04 or (La.

Sr) 2NiF< type oxides such as 2CuO4 are mentioned.

In these materials, a significantly higher Tc of 30 to 50 than that of conventional materials was observed, and in addition, Ba, Y.

Superconducting materials made of Cu oxides have a Tc of 70 or more.
has also been reported.

Problems to be Solved by the Invention However, since these superconducting materials are obtained as sintered bodies, they are generally brittle and must be handled with care. That is, it easily breaks or cracks due to mechanical stress, and particularly when it is made into a wire, it breaks very easily, so there are major restrictions on its actual use.

In addition, with sintered superconducting materials, it is difficult to form a completely homogeneous polycrystalline body consisting only of particles with superconducting properties, and as a general property of superconductors, localization may occur due to external magnetic fields or fluctuations in cooling temperature. The superconducting state may be broken. However, this type of sintered superconducting material has lower thermal conductivity and higher electrical resistance than conventional superconducting materials. Therefore, as mentioned above, at a location where the superconducting state is broken, local heat generation occurs due to the current flowing through the superconductor, and when the superconductor comes into contact with the cooling medium, explosive vaporization of the cooling medium is induced. Therefore, in conventional metal-based superconductors, the superconductor is formed as a thin filament, and a large number of filaments are integrally formed with a good conductor such as Cu, which serves as a heat conductor and a current bypass in case the superconductor breaks. He was avoiding danger.

On the other hand, it is difficult to adopt the above-mentioned configuration with the superconducting sintered bodies with high Tc that have been developed in recent years, and it is currently difficult to use them as wire materials. .

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to create a new material that can use a superconducting material having a high Tc as a wire material with high stability of superconducting properties and a large degree of freedom in shape. The object of the present invention is to provide a structure of a superconducting material.

In the following description, the superconducting critical temperature is expressed as Tc,
The end temperature of the phase transition at which the electrical resistance of the superconductor becomes completely zero is expressed as Tcf, and the difference between Tc and Tcf is expressed as ΔT.

Means to solve problems That is, according to the present invention, General formula: (AX-I BX) c, D.

(However, A is a type of element selected from group ■a N III a of the periodic table, and B is a type of element selected from group IIa, ff1 of the periodic table.
It is a type of group a element selected from elements that include the same elements as A, C is at least one type selected from elements of group Ib, IIb, mb, and a of the periodic table, and D is O, B (I
is at least one selected from N, C (carbon), N, F, and S, X is the atomic ratio of B to A+B, and is 0.1≦x≦0.9, and y and 2 teeth(
When Ax-+Bx) is 1, 0.4≦y≦3
．． A flexible superconducting material characterized by comprising a composite oxide thin film having a thickness of 1 μm or less and having an atomic ratio of 0.1≦Z≦5, and a flexible substrate that supports the thin film. is provided.

Function The main feature of the present invention is that a perovskite or pseudo-perovskite oxide film having superconductivity is formed as a thin film having a thickness of 1 μm or less on a flexible substrate.

That is, even in the case of a sintered body having low brittleness, as the thickness thereof becomes thinner, the effect of internal stress on itself can be virtually ignored, and bending becomes considerably free.

However, as a current transmission medium, it is desirable that the cross-sectional area be wide because there is a limit to the current density. Therefore, as a preferred embodiment of the present invention, a flexible superconducting material having a sufficient critical current density can be obtained by stacking a plurality of flexible substrates each carrying a superconducting thin film.

Furthermore, by forming the substrate material from a conductor at this time, the substrate can have a function as a current bypass when superconductivity is broken as described in the previous section.

Although various methods can be applied to form the superconducting thin film as described above, particularly preferred methods for the present invention include:
A physical vapor deposition method using a superconducting material obtained as a perovskite or pseudo-perovskite oxide sintered body, a method of thinning the perovskite or pseudo-perovskite oxide by powder coating, etc. can be mentioned.

The superconducting sintered body used in these methods is obtained as follows. That is, for example, elements belonging to groups 1a and ma of the periodic table, such as a combination of Ba and Y, and elements Ib, nb, I[[b,
(2) Produced by sintering powders of oxides, carbonates, nitrates, or sulfates of any of the elements belonging to group a. still,
When used as a target, it may be either pre-sintered or permanently sintered. Further, a fired body, a powder obtained by crushing a sintered body, or a bulk sintered body may be used. In particular, when a sintered body powder is used, the evaporation efficiency of the target is good, so a high degree of film formation can be obtained by using a powder having a particle size in the range of 0.03 to 2 mm.

The present invention will be explained below with reference to examples, but it goes without saying that the technical scope of the present invention is not limited to these examples in any way.

EXAMPLE First, an apparatus used for producing a superconducting material according to the present invention will be described. FIG. 1 is a schematic diagram of a high frequency sputtering apparatus used for producing the superconducting oxide thin film of the present invention.

The apparatus shown in FIG. 1 includes a chamber 1, a target 2 disposed in the chamber 1, a sputtering atom 3 placed side by side with the target for sputtering the target with sputtering atoms, and a source target 2 disposed facing the source target 2. It mainly consists of a substrate 4 on which a thin film is formed. The chamber 1 is connected to a vacuum pump (not shown) through a port 7, so that the interior thereof can be evacuated.

A bias voltage is applied to the substrate 4 using a high voltage power supply 5. A heating heater 6 is further attached to the substrate 4, and the temperature of the substrate can be adjusted.

Furthermore, a gas introduction hole 8 is attached to the chamber 1 .

First, as the raw material target 2, BaCo3, Y2 (C
o3)3 CuO powder with atomic ratio Ba/ (Ba+Y
) was 0.2, pre-sintered at 800°C, crushed, molded, and finally sintered at 1100°C to produce a sintered block.

Using the sputtering apparatus shown in FIG. 1, the above sintered block was used as a target, and the width was 5 Q mm.

A superconducting thin film was formed on the surface of a stainless steel tape-shaped substrate with a length of 150 mm, thickness o, and Q3 mm. Note that the film forming conditions are as follows.

Oxygen partial pressure 3 Xl0-2 Torr.

Ar partial pressure 3xlO-2 Torr.

The substrate temperature was 910° C., the substrate bias voltage was −50 V1, the high frequency power was 5 W ictl, the distance between the substrate and the target was 3 Q mm, and the film forming rate was 4 people/sec, and the film was formed to a thickness of about 0.5 μm.

Next, samples were prepared to measure the resistance of each of the obtained thin films. In the sample for resistance measurement, a pair of electrodes were further formed by vacuum evaporation on both ends of the thin film formed on the substrate 4, and lead wires were soldered to the Al electrodes.

The oxygen partial pressure inside the chamber was set to 3 x 10-”Torr.
In the thin film produced by the method of the present invention, the superconducting phenomenon began at a temperature of about 89° C., and became a complete superconductor below 78° C.

Furthermore, when the above superconducting material was bent with a simple jig to a radius of curvature of 5 Qmm with the superconducting thin film inside, the critical temperature was similarly measured, and the temperature at which the superconducting phenomenon began was found to be approximately 88 and 77. Below, it became a perfect superconductor, and no significant deterioration in properties was observed. Further, even though it was bent to a radius of curvature of 3Q+ro++, no peeling of the superconducting thin film occurred.

Effects of the Invention As detailed above, the superconducting material according to the present invention supports a mechanically fragile superconducting sintered body having a high critical temperature with a flexible substrate, and also reduces the thickness of the sintered body itself. By limiting the stiffness, flexibility is imparted to the superconducting material. Moreover, the superconducting material according to the present invention is configured so that the substrate is made of a conductor so that it also functions as a current pass when the superconductivity is broken.

Thus, the present invention provides a novel superconducting material that has a high and stable Tc, is extremely easy to handle, and can be widely used as wire rods or small parts.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of a sputtering apparatus used to carry out the method of the present invention. (main reference number)

Claims (7)

[Claims] (1) General formula: (A_x_-_1B_x)C_yD_z
(However, A is an element selected from group IIa and IIIa of the periodic table, and B is an element selected from group IIa and IIIa of the periodic table.)
, C is at least one element selected from elements in groups Ib, IIb, IIIb, and VIIIa of the periodic table, and D is O, B (boron), and C (carbon). ), N, F, and S, x is the atomic ratio of B to A+B, and 0.
1≦x≦0.9, and y and z are (A_x_−_1
B_x) is 1, then 0.4≦y≦3.0, 1≦z
A flexible superconducting material comprising: a composite oxide thin film having a thickness of 1 μm or less and having an atomic ratio of ≦5; and a flexible substrate supporting the thin film. (2) The flexible superconducting material according to claim 1, wherein the composite oxide thin film is formed by physical vapor deposition. (3) The flexible superconductor according to claim 1, wherein the composite oxide thin film is formed of powder of the composite oxide adhered to the flexible substrate. Material. (4) The flexible superconducting material according to any one of claims 1 to 3, wherein the flexible substrate is a conductor. (5) The flexible superconducting material according to any one of claims 1 to 4, characterized in that a plurality of substrates on which the thin film is mounted are laminated. (6) The flexible superconducting material according to any one of claims 1 to 5, wherein the elements A and B are Ba and Y, respectively. (7) The flexible substrate according to any one of claims 1 to 6, wherein the flexible substrate is made of Cu, Fe, Ni, Co, or Al. superconducting material.