JPH01123405A - Manufacture of superconducting power lead - Google Patents

Abstract

PURPOSE:To decrease the yielding amount of Joule's heat and to reduce heating due to contact resistance, by using an oxide superconductor as the main body of a power lead, using low resistance metal as terminals, and limiting the yield of Joule's heat accompanying the conduction of current to the one at both electrodes. CONSTITUTION:The inside of a low resistance metal tube 3 is filled with oxide superconductor powder or its starting raw material powder 1 at a high density, and heat treatment is performed. A part or all of the metal tube 3 is removed, and a rod shaped body 8 is obtained. The rod shaped body 8 is heat-treated in an atmosphere including oxygen. Terminals 6 are formed with low resistance metal at both ends of the rod shaped body 8 before or after the heat treatment. A coating 9 comprising a high resistance material or an insulating material is formed on the outer surface of the heat-treated rod shaped body 8 between the terminals 6. Thus the yielding amount of the Joule's heat is decreased and heating due to contact resistance is reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to the manufacture of lead wires used for electrically connecting a ¥4 conductive wire cooled with liquefied gas or the like to an external device. The present invention relates to a method for manufacturing a superconducting power lead using an oxide superconductor.

(Prior Art) Conventionally, alloy-based or intermetallic compound-based superconducting wires, which have been put into practical use in MHI, accelerators, etc., are used after being immersed in liquid helium and cooled to below a critical temperature. Liquid helium is thermally shielded from the external environment by a vacuum chamber and various types of insulation materials. On the other hand, the conductive wire s' and the external device are electrically connected by a power lead made of a normally conductive metal such as copper, which is disposed through the vacuum chamber and the heat insulating material.

In this way, in conventional superconducting wires, the entire structure is thermally shielded by a vacuum layer and heat insulating material, but since the superconducting wires are connected to external equipment by power leads made of normal conducting metal, external heat,
There has been a problem in that Joule heat due to energization of the power leads enters, thereby accelerating the evaporation of liquid helium, which is a refrigerant.

(Problem to be solved by the invention) As described above, power leads for electrically connecting superconducting wires cooled with liquid helium and external equipment have conventionally been made of normally conductive metals, There has been a problem in that evaporation of the refrigerant is accelerated due to Joule heat generated due to this and heat intrusion from the outside through the power lead.

The present invention was made to solve these conventional difficulties, and an object of the present invention is to provide a method for manufacturing a superconducting power lead that can reduce the generation of Joule heat due to energization and the heat penetration through the power lead. shall be.

[Structure of the Invention] (Means for Solving the Problems) That is, the method for manufacturing a superconducting power lead of the present invention includes:
A step of filling a low-resistance metal tube with oxide superconductor powder or its starting material powder at high density and heat-treating the same; and a step of heat-treating the rod-shaped body obtained by removing the inside of the low-resistance metal tube in an oxygen-containing atmosphere. , a step of forming terminals with a low-resistance metal at both ends of the rod-shaped body before or after the heat treatment, and a coating of a high-resistance material or an insulating material on the outer periphery of the rod-shaped body subjected to the heat treatment, spanning between the terminals. The method is characterized in that it has a step of forming.

Although various Φ oxide superconductors can be used in the present invention, the use of a perovskite-type oxide superconductor containing a rare earth element, which has a high critical temperature, has a particularly great practical effect.

The above-mentioned oxide superconductor containing a rare earth element and having a perovskite structure may be one that can realize a superconducting state, and may be an LnBa Cu O-based 2 3 7-δ (δ represents an oxygen defect and is usually a number of 1 or less). , Ln is Y, L
a, Sc, Nd, Sn+, Eu, Gd, Dy
, No, Er, Tn, Yb, and Lu, a part of Ba can be replaced with sr, etc.);
Examples include oxides having a perovskite type in a broad sense, such as a layered herovskite type such as La-Cu-0 type. Rare earth elements are also broadly defined to include Sc, Y, and Eu-based elements.

In addition to the Y-Ba-Cu-0 system, representative systems include systems in which V is replaced with rare earth elements such as Eu, ay, -0 series, 5r-La-
Examples include Cu-0 series and systems in which S' is replaced with Ba or Ca.

The oxide superconductor used in the present invention can be obtained, for example, by the manufacturing method shown below.

First, the constituent elements of the perovskite oxide superconductor, such as Y, Ba, and Cu, are thoroughly mixed. When mixing, Y
Oxides such as O and CuO can be used as raw materials. In addition to these oxides, compounds such as carbonates, nitrates, and hydroxides that are converted to oxides after firing may also be used. The elements constituting the perovskite oxide B conductor may be mixed in a stoichiometric composition, but may be mixed to some extent. There is no problem even if there is a deviation due to manufacturing conditions, etc.
For example, in the Y-Ba-Cu-0 system, Ba 2 n + ol and Cu 3 nol are f5 quasi-compositions for Y 1 lot, but in practice, Ha
A deviation of about Z±0.6 not, Cu 3±0.2 lol is not a problem.

After mixing the above-mentioned raw materials, they are calcined and pulverized into a desired shape, and then fired at about 850 to 980°C. Calcining is not necessarily necessary. Preferably, calcination and firing are performed in an oxygen-containing atmosphere where sufficient oxygen can be supplied. After firing into a desired shape, it is heat-treated in an oxygen-containing atmosphere to impart superconducting properties. The above heat treatment is usually performed at 600° C. or lower while slowly cooling.

The oxide superconductor thus obtained has oxygen defects δ
Oxygen-deficient perovskite structure (LnBa
Cu O (δ is usually 1 or less)).

(δ Note that Ba can also be replaced with at least one of S, Ca, and a part of Cu can be replaced with Ti, V, Cr,
It can also be replaced with Hn, Fe, C01N1, ln, etc.

The amount of this substitution can be set as appropriate within a range that does not reduce the superconducting properties, but too much substitution will reduce the superconducting properties, so it should be set at 80 II o l % or less, and moreover, in practical terms, it should be about 20 II o 1 % or less. .

Further, the low resistance metal used in the present invention is preferably silver or gold, and the high resistance material or insulating material is a high resistance material such as a synthetic resin such as an epoxy resin or a synthetic resin reinforced with an inorganic fiber material. Preferably, it is an insulating material.

The superconducting power lead according to the present invention is manufactured using the above-described oxide superconductor, low-resistance metal, and high-resistance material or insulating material, for example, as follows.

First, an oxide superconductor obtained by firing a starting material or the starting material itself is pulverized by a known means such as a ball mill.

Next, this oxide superconductor powder or its raw material powder is filled into a low resistance metal tube such as silver or gold, and after surface reduction processing is performed using a die, Turk's head, etc.
A composite material is obtained by heat treatment at 80°C. The parts of the low-resistance metal layer of the obtained composite material other than the parts that will become the terminals at both ends were removed by etching, cutting, etc., and
The oxide superconductor powder or its raw material powder is fired at 0 to 980°C, and then slowly cooled to below 600°C at a cooling rate of about 1°C/min to add oxygen to the oxygen vacancies in the packed crystal ellipse of the oxide superconductor. will be introduced to improve superconducting properties.

After that, synthetic resin such as epoxy resin or inorganic resin is applied to the outer periphery of the exposed oxide superconductor where the metal layer has been removed.
A superconducting power lead can be obtained by coating with a high resistance material such as a synthetic resin or an insulating material reinforced with S fiber material.

Note that it is also possible to use low resistance metals other than silver and gold as the low resistance metal, but in this case, a second heat treatment is performed after all the low resistance metals are removed, and after the heat treatment, the terminals at both ends are Plating method 1. It is preferable to coat with a low resistance metal using a vapor deposition method or the like. This is because when a low resistance metal other than silver or gold is used, it may react with oxygen in the oxide superconductor during heat treatment and deteriorate the superconducting properties.

In addition, if necessary, terminal fittings made of copper, aluminum, etc. may be attached to the terminals by soldering, crimping, cold compression, etc. Furthermore, when used as a removable power lead, terminal fittings made of copper, aluminum, etc. may be attached to the terminals. Depending on the requirements, the terminals may be plated with a low melting point soft metal such as indium.

(Function) In the method for manufacturing a superconducting power lead of the present invention, a power lead body and 11. Since an oxide superconductor is used in this process, Joule heat is generated only at the picture electrode when electricity is applied.
The amount of Joule heat generated can be reduced. Also,
Since the terminals are made of low-resistance metal, there is little heat generation due to contact resistance at the connection.

Furthermore, although it depends on the composition and density, the thermal conductivity of oxide superconductors is 7 to 10 Wn in the v-ea-cu-, o system.
-1 (90K), and the thermal conductivity of copper is 483Wn-
' be able to.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Example 2 mol of BaCO3 powder was used as a raw material for the oxide superconductor.
%, Y2O3 powder 0.57IO1%, CuO powder 3io
1%, mix them thoroughly and heat them at 900℃ in the atmosphere for 8 hours.
After firing for an hour, the oxide superconductor powder was crushed using a ball mill to obtain an oxide superconductor powder.As shown in FIG.
One end of 00 mm was filled into a steel pipe 3 sealed with a silver material 2, and then plugged with a silver material 4. Then, as shown in FIG. 2, the area was reduced using a die 5 until the outer diameter became snn. After heat treatment at 950℃ for 5 hours, the length iooma
After coating the end faces with silver by sputtering, as shown in Fig. 3, a silver layer of 201111 is left as a terminal 6 from both ends, and the other silver layer is removed using a cutting tool 7 to form a bar shape. Obtained body 8. This rod-shaped body 8 was heat-treated at 950°C for 10 hours in an oxygen-containing atmosphere, and then slowly cooled to 600°C or less at a rate of 1°C/min to introduce oxygen into the oxygen vacancies in the crystal #I of the oxide superconductor. , improved superconducting properties. Thereafter, as shown in FIG. 4, the removed portion of the silver layer was covered with epoxy resin to provide an insulator layer 9, thereby obtaining a superconducting power lead 10.

The critical current density of this superconducting power lead at 90K is 260^/-1, and the thermal conductivity is 11Wl-I K-1,
The total amount of heat generated when a current of 50 A was applied was 0.31 mW.

In the superconducting power lead of this embodiment, as shown in FIG. Almost the same characteristics were obtained when a layer of a soft metal with a low melting point such as indium was provided on the outside.

In FIGS. 1 to 5, common members are designated by the same reference numerals.

[Effects of the Invention] As explained above, the superconducting power lead obtained according to the present invention generates less Joule heat when energized.
Furthermore, since the thermal conductivity is low, even when used to connect a superconducting wire using a coolant such as liquid helium to an external device, heat intrusion from the outside can be reduced.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views showing the manufacturing procedure of the superconducting power lead according to the present invention, and FIG. 5 is a cross-sectional view showing the superconducting power lead obtained according to the present invention with terminal fittings provided on the terminals. 1... Oxide superconductor 2... Steel pipe 6... Terminal 8... Rod-shaped body 9. ......Insulator layer 10...Superconducting power lead applicant
Toshiba Corporation Patent Attorney Sasa Suyama - Figure 1 Figure 2 Figure 3

Claims (5)

[Claims] (1) A process of filling a low-resistance metal tube with oxide superconductor powder or its starting material powder at high density and heat-treating the same, and removing a part or all of the low-resistance metal tube to oxygenate the rod-shaped body obtained. a step of heat-treating in a containing atmosphere; a step of forming terminals with a low-resistance metal at both ends of the rod-shaped body before or after the heat treatment; 1. A method for manufacturing a superconducting power lead, comprising the step of forming a coating of a resistive material or an insulating material. (2) The method for manufacturing a superconducting power lead according to claim 1, wherein the low resistance metal is silver or gold. (3) The method for manufacturing a superconducting power lead according to claim 1 or 2, wherein the oxide superconductor is a perovskite-type oxide superconductor containing a rare earth element. (4) The oxide superconductor contains Ln element (Ln is at least one element selected from rare earth elements), Ba and C
The method for manufacturing a superconducting power lead according to any one of claims 1 to 3, characterized in that the superconducting power lead contains u in an atomic ratio of substantially 1:2:3. (5) The oxide superconductor is LnBa_2Cu_3O_7
A method for manufacturing a superconducting power lead according to any one of claims 1 to 4, which has an oxygen-deficient perovskite structure represented by _-_δ (δ represents an oxygen defect). .