JPH057026A - Oxide superconductor electrode - Google Patents

Abstract

PURPOSE:To obtain arm oxide superconductor electrode wherein isolated noble metal particles in superconductor are reduced, and uneveness of superconducting characteristics of the connection part of an electrode part and the superconductor is decreased. CONSTITUTION:In an oxide superconductor electrode having a structure wherein one or two or more kinds of noble metal 2 selected out of a group composed of silver, gold and palladium are dispersed in oxide superconductor 1, the noble metal 2 is dispersed in the state that the volume fraction decreases from the electrode end portion along the longtudinal direction.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an oxide superconductor electrode.

[0002]

2. Description of the Related Art FIG.
Genesis) 128 (1988) 734-736, which is a schematic sectional view of an electrode using a low contact resistance connection. With this technology, oxides and silver (or silver oxide) that become superconductors by heat treatment
After mixing and molding, heat treatment was performed.
(1) is an oxide superconductor, (2) is a noble metal powder (silver), (3) is a current lead wire, and (4) is a current lead connecting metal.

The conventional low contact resistance electrode is constructed as described above, and for example, in order to supply a current, a current lead wire is connected on the surface with indium, solder or the like.

[0004]

In the conventional low contact resistance electrode as described above, it is necessary to add a large amount of noble metal, but the noble metal isolated inside the superconductor does not contribute to the reduction of contact resistance. However, the addition of a large amount of noble metal lowers the volume ratio of the superconductor, so that there is a problem that the superconducting characteristics at the connecting portion between the electrode portion and the superconductor are skipped.

The present invention has been made in order to solve the above problems, and oxidation in which the isolated noble metal particles in the superconductor are reduced and the jump in the superconducting characteristics of the connecting portion between the electrode portion and the superconductor is reduced. An object of the present invention is to provide a superconductor electrode.

[0006]

The oxide superconductor electrode according to the present invention has a structure in which one or more noble metals selected from the group consisting of silver, gold and palladium are dispersed in the oxide superconductor. In the oxide superconductor electrode having,
The noble metal is dispersed in a state where the volume fraction decreases from the end of the electrode along the longitudinal direction.

Also, the oxide superconductor electrode of the present invention has a structure in which the connectivity between the noble metal particles is improved by imparting a gradient to the volume fraction even from the electrode surface toward the inside.

In the oxide superconductor electrode of the present invention,
Because of the structure that gives distribution to the volume fraction of precious metal,
A region containing noble metal and a region not containing noble metal are generated, and a noble metal density gradient is given in the longitudinal direction of the electrode. In order to make the surface fraction of the noble metal on the electrode surface have a gradient, it is necessary to have a structure in which the region containing the noble metal or the region not containing the noble metal is provided with a gradient in the longitudinal direction. At this time, it is possible to adopt a structure in which the region containing the noble metal is entirely covered with the noble metal.

[0009]

In the oxide superconductor electrode structure as described above, the volume fraction of the noble metal has a gradient in the longitudinal direction of the electrode, and the superconducting characteristics are not jumped at the connecting surface between the electrode portion and the superconductor portion.
Since a gradient of the volume fraction of the noble metal is generated from the surface of the oxide superconductor electrode toward the inside, the connectivity between the noble metal particles can be improved, and thereby the isolated noble metal particles can be reduced. Further, in the region of the electrode portion covered with the noble metal, the current lead wire can be easily connected by using the low melting point metal.

[0010]

EXAMPLE 1 FIG. 1 is a schematic view of the surface of an oxide superconductor electrode showing an example of the present invention. Further, FIG. 2 is a manufacturing process diagram of the oxide superconductor electrode of the present invention. In powder production, Bi
₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ , CuO (Bi-P
b) After mixing so as to have a molar ratio of ₂ Sr ₂ Ca ₂ Cu ₃ O _y ,
Heat treatment was performed in air at 845 ° C. for 50 hours. This was crushed and molded, and then the same heat treatment was performed as the crushed raw material powder, which was 2 mm ^t × 10 mm ^w × 100 mm ^l , and the pressing pressure was 0.7.
Molded at ton / cm ² . Next, the oxide molded body was heat-treated in air at 845 ° C. for 100 hours. The density of the sintered body at this time was about 50% of the theoretical density. After firing, an airtight pressure-sensitive adhesive sheet having holes in the electrode part was attached to the sintered oxide molded body. Here, the holes are arranged in the adhesive sheet,
The arrangement of the holes makes it possible to determine the degree of decrease in the gradient of the volume fraction from the electrode end portion in the longitudinal direction. In addition,
The shape of the holes need not be circular, and may be the shape shown in FIG. On the other hand, the colloidal solution for impregnating the oxide molded body was prepared by weighing isopropyl alcohol and silver oxide at a weight ratio of 1: 1 and mixing them in a ball mill. Next, the oxide molding and the colloid solution were sealed in a container made of raw rubber, and this was sealed using a hydrostatic pressure machine (CIP) 1.
The pressure was kept at 0 ton / cm ² for 10 minutes for impregnation. The taken-out sample was peeled off the pressure-sensitive adhesive sheet, dried with alcohol at 150 ° C., densified by pressurizing at 4 ton / cm ² , and further heat-treated in air at 845 ° C. for 100 hours to obtain an electrode.

As shown in FIG. 1, since the coating is not performed in the process and therefore the noble metal invades or deposits, the distribution of the surface pores in the longitudinal direction has a gradient, so that the joint between the electrode portion and the superconductor portion is formed. Due to the small volume fraction of the noble metal, no significant jump in superconducting properties occurs. Further, FIG. 3 is a schematic view of a vertical cross section of the electrode manufactured in this example. As shown, the density of the noble metal powder is higher on the surface of the oxide superconductor electrode, and the bondability between the noble metals, between the noble metal and the current lead bonding metal, and between the noble metal and the oxide is improved. As a result, a low contact resistance electrode having a level of 10 ^-2 micro ohm cm ² was obtained.

In Example 1, the exposed form of the noble metal at the electrode portion of the coated oxide superconductor electrode was a large number of holes having a density distribution gradient in the longitudinal direction, but as shown in FIG. Of course, it is also possible that the shape is such that the noble metal is coated so as to be residually distributed.

Further, the noble metal on the surface of the electrode obtained in the embodiment is dispersed in the dot-shaped holes. It is possible to completely cover the inside of the hole with a noble metal in order to improve the connectivity with the current lead wire and realize a low contact resistance. It can be manufactured by placing and pressing a noble metal (for example, silver powder, gold powder, gold oxide powder, palladium powder) at the time of pressurization and densification in the manufacturing process, and heat-treating this.

[0014]

EFFECTS OF THE INVENTION Since the present invention has the electrode structure as described above, it exhibits the effects as described below. Since the distribution of the noble metal is made to have a gradient in the longitudinal direction, a large jump does not occur in the superconducting characteristics at the connecting portion between the electrode and the superconductor. Since the volume fraction of the noble metal was given from the electrode surface toward the inside, the bondability between the noble metals was increased, and the isolated noble metal inside the superconductor was reduced. Further, since the noble metal near the electrode surface is contained at a high density (substantially completely), the bondability with the current lead connecting metal is improved. Due to these synergistic effects, low contact resistance is possible, and the oxide superconductor electrode of the present invention can be suitably used for electrodes such as superconducting magnets and current leads.

[Brief description of drawings]

FIG. 1 is a schematic view of a surface of an oxide superconductor electrode showing an example of the present invention.

FIG. 2 is a process drawing of a manufacturing process according to an embodiment of the present invention.

FIG. 3 is a schematic sectional view of an oxide superconductor electrode obtained in Example 1 of the present invention.

FIG. 4 is a view showing an oxide superconductor electrode according to another embodiment of the present invention.

FIG. 5 is a schematic sectional view of a conventional low connection resistance electrode.

[Explanation of symbols]

 1 oxide superconductor 2 noble metal powder 3 current lead wire 4 current lead wire junction metal

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[Procedure amendment]

[Submission date] July 9, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

Since the present invention has the electrode structure as described above, the following effects are exhibited. Since the distribution of the noble metal is made to have a gradient in the longitudinal direction, a large jump does not occur in the superconducting characteristics at the connecting portion between the electrode and the superconductor. Since the volume fraction of the noble metal was given from the electrode surface toward the inside, the bondability between the noble metals was increased, and the isolated noble metal inside the superconductor was reduced. Further, since the noble metal near the electrode surface is contained at a high density (substantially completely), the bondability with the current lead connecting metal is improved. Due to these synergistic effects, low contact resistance is possible, and the oxide superconductor electrode of the present invention can be suitably used for electrodes such as superconducting magnets and current leads.

Continued Front Page (72) Inventor Shinichi Kinouchi 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Material Research Laboratory (72) Inventor Shin Utsunomiya 8-1-1 Tsukaguchihonmachi, Amagasaki Material Mitsubishi Electric Corporation Material In the laboratory

Claims (1)

Claim: What is claimed is: 1. An oxide superconductor electrode having a structure in which one or more noble metals selected from the group consisting of silver, gold and palladium are dispersed in the oxide superconductor, An oxide superconducting electrode, in which a noble metal is dispersed in a state where the volume fraction decreases from the end of the electrode along the longitudinal direction.