JPH02216712A - Oxide high temperature superconductor and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture an oxide high temperature superconductor film of Bi-Sr-Ca-Cu-O family with the oxide unified with Cu by causing the Bi-Sr-Ca-Cu- O-based oxide to adhere to the surface of a metallic substrate of copper or copper alloy or to copper oxide formed on the metallic substrate, and heat- treating the film in the air, vacuum or in a reducing atmosphere. CONSTITUTION:As a metallic substrate, a substrate of copper or copper alloy with its surface covered with copper oxide is used. Oxide of Bi-Sr-Ca-Cu-O family temporarily baked in advance is made to adhere to the surface of the metallic substrate through a suitable process such as application, deposit, sputter, etc. The copper composite with its surface deposited with the Bi-Sr-Ca-Cu-O- based oxide is heat-treated in the air, vacuum, or reducing atmosphere to diffuse Cu in the oxide. The heat-treated copper composite is cooled not rapidly but gradually preferably in non-oxidizing atmosphere or in vacuum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to the application of Bi- The present invention relates to an oxide high temperature superconductor to which a Sr-Ca-Cu-0 based oxide high temperature superconducting film is firmly attached, and a method for manufacturing the same.

(Prior Art and Problems to be Solved) The development of superconducting materials in recent years has been remarkable, and various high-temperature superconducting materials have been reported, and research on oxide-based high-temperature superconducting materials is particularly active.

Examples of ways to use such high-temperature superconducting materials include methods in which the high-temperature superconducting material itself is formed into various shapes, and methods in which the superconducting material is formed on the surface of a substrate.

Conventionally, among the latter methods, oxide high-temperature superconductors using metal as a substrate have been produced by using silver as the substrate as a conductor and depositing crystals such as magnesium oxide or strontium titanate on the surface. It has only been reported.

However, since the method of using silver as a metal substrate is limited to specific applications, methods using metals that are often used as a substrate, for example, - Is it possible to replace copper wires and copper plates, which are commonly used for power transmission, with metal substrates? However, if a method for directly depositing an oxide superconductor on top of the superconductor could be developed, its utility would be extremely valuable.

The object of the present invention is to provide an oxide high-temperature superconductor film that is firmly adhered to copper or a copper alloy as a conductor of electricity, etc., with respect to the integration of a high-temperature superconductor and a metal in the above-mentioned conventional method. The purpose is to provide a high temperature superconductor.

Another object of the present invention is to provide a method for firmly adhering an oxide high-temperature superconductor onto copper or a copper alloy as a conductor of electricity or the like.

(Means for Solving the Problem) In order to achieve the above object, the present inventor has developed a method using a copper substrate and a Bi
An attempt was made to synthesize a superconducting film by reacting -Sr-Ca based oxides.

That is, Bi, ○3. An appropriate amount of SrCO and CaCO2 (2: 1: 1.1: 1: 1) was mixed and calcined at 800°C for 1 hr. The films were screen-printed on a CuO substrate whose surface was coated with CuO, and fired in an electric furnace to cause a solid-state reaction, and the superconducting properties and crystal structure of the obtained films were investigated.

As a result, superconducting properties were not obtained in the case of the Cu substrate. This is C: u+1/2○2→C on the Cu substrate.
This is thought to be because the u○ reaction takes priority.

On the other hand, in the case of Cu○ substrate, C
A phase at 80 oriented in (0,0,Q) was formed on the uO substrate, and a peak of the phase at 110 was observed at 2 hr and 5 hr. This is considered to be because the diffusion of Cu in the substrate was suppressed and the oxidation reaction of Cu took priority. Therefore, it was found that in order to create a superconductor, it is necessary to suppress the diffusion of Cu in the substrate.

Therefore, in order to suppress the diffusion of Cu, we conducted a similar experiment with a Cu substrate pre-oxidized to produce copper oxide on its surface, and found that a film with excellent superconducting properties without cracks could be formed. .

This is where the present invention is made.

That is, the present invention provides a metal substrate made of copper or a copper alloy, and a Bi-Sr-
The gist of the present invention is an oxide high-temperature superconductor characterized in that a Ca-Cu-0-based oxide high-temperature superconducting film is formed.

In addition, the manufacturing method involves depositing a Bi-Sr-Ca based oxide on a metal substrate made of copper or a copper alloy, or on the copper oxide formed on the metal substrate or on the surface of the metal substrate. , B i − in which the oxide and Cu are integrated by heat treatment in air, vacuum, or a reducing atmosphere.
This method is characterized by obtaining an S r -Ca -Cu -0-based oxide high-temperature superconducting film.

The present invention will be explained in more detail below.

(Function) First, the present invention is based on the premise that the metal substrate is made of copper or a copper alloy and has copper oxide on its surface.

Such a metal substrate may have copper oxide already formed on its surface, or it may have copper oxide formed through oxidation treatment such as thermal oxidation (e.g., about 800°C) or plasma oxidation in an oxygen-existing atmosphere. It is also possible to partially oxidize the surface of the metal substrate, which may be produced to a suitable thickness, preferably by plasma oxidation. Of course, various shapes such as a gold copper plate, a steel pipe, a wire, etc. are possible.

As the copper oxide, there is no problem even if cupric oxide (CuO) or cuprous oxide (CuzO) coexists. Further, the thickness of the copper oxide layer can be determined appropriately, and is approximately several tens of microns, for example.

Copper or a copper alloy is used as the metal substrate, but it is sufficient if at least the surface layer of the substrate is made of copper or a copper alloy. For example, if the main body of the substrate is made of another material, only the surface layer is made of copper or a copper alloy. It may be a structure consisting of.

Next, on the surface of a metal substrate whose surface is coated with copper oxide,
Bi-Sr-C pre-calcined (e.g. 800℃xlhr)
The a-0 series oxide is deposited by appropriate means such as coating, vapor deposition, sputtering, etc. In this case, it is desirable that the thickness be equal to or greater than that of copper oxide.

Bi-Sr-Ca-0 type oxides include pb, B
It is desirable that the material is a substance containing an oxide such as a, Ti, or Te.

The molar ratio of Bi:Sr:Ca in this oxide is the 1st rj! It is desirable to adjust it so that it falls within the shaded range of the triangular composition diagram shown in R. Preferably, Bi:Sr:Ca
=2:1:1.

The copper composite having the Bi-Sr-Ca-0-based oxide adhered to its surface in this manner is heat-treated in air, under vacuum, or in a reducing atmosphere to diffuse Cu into the oxide.

It is preferable to carry out the heat treatment in a vacuum or in a reducing atmosphere, but please note that if heat treatment is carried out in an oxidizing atmosphere, the oxidation of the substrate wire will proceed further, which may deteriorate the superconducting properties of the high-temperature superconductor produced. do. It is desirable that the heat treatment be maintained at a temperature range of 800 to 900°C for several tens of minutes to several hours.6 As a heat treatment method, oxidized steel is partially generated on the gold scrap substrate, and Bi-Sr-Ca is formed only on the oxidized steel. When -0 series oxide is deposited, it is preferable to use a local heating means using a light beam that generates heat, such as a laser.

The heat-treated rope composite can be used without rapid cooling.
Cool slowly in a non-oxidizing atmosphere or in a vacuum if possible. When rapidly cooled, cracks are generated in the superconductor due to thermal stress caused by the difference in coefficient of thermal expansion between the high-temperature superconductor and copper oxide in the first surface layer, degrading the superconducting properties.

The material obtained in this way is a metal-superconductor composite element that is integrated with a strong adhesive chemical bond on the copper or copper alloy of the metal substrate, either directly or via copper oxide. In the latter case, as shown in FIG. 3, oxidized steel (CuOx) and superconductor are laminated in this order on the copper or copper alloy of the metal substrate, and the copper oxide layer has Cu2O on the substrate side. Further, CuO exists in a rich state on the superconductor side.

The method of the present invention has the above configuration, and a typical process is as shown in FIG. 2, but the following embodiments are also possible.

First, Bi is applied to the surface of plasma-oxidized copper by sputtering or the like.
-Sr-Ca-0 based oxide is deposited in-situ (in-
In situ), it is possible to obtain a superconductor by heating the substrate, and the manufacturing steps are significantly reduced.

In addition, only the inside of the copper pipe is oxidized, and Bi
A copper-coated superconducting wire can be made by packing Sr-Ca-○-based oxide and heat-treating it.

Furthermore, as an application to semiconductor processing, it is also possible to pattern copper, control the oxidized portion of the copper, and make only that portion a superconductor.

Next, examples of the present invention will be shown.

(Example) A copper plate with a purity of 99.9% was heated at 800°C x 2 using an electric furnace.
An oxidation treatment was performed for several hours to form a copper oxide film of several tens of μI on the surface of the copper plate.

Also, in advance, Bi: Sr: C mini 2: 1:
Bi-Sr-Ca- weighed so that the molar ratio is 1 (molar ratio)
The 0-series compound was calcined at 800°C for 2 hours and pulverized.

This oxide powder was suspended in an ethanol solution and screen printed onto the copper plate to adhere to the surface. The thickness at this time is approximately equal to or greater than the thickness of the copper oxide film.

Then, after drying this composite, A at a temperature of 870°C
It was quickly charged into a tube furnace whose atmosphere was adjusted to r10□=100/1, heated for about 30 minutes to 1 hour, and cooled while flowing the same mixed gas (Ar102=100/1) into the furnace. In this case, it is preferable to cool it as quickly as possible, but cooling outside the furnace should be avoided.6 The X-ray diffraction pattern of the obtained oxide film is shown in FIG.

Further, the resistance curve measured by the four-terminal method (current 0.1 mA, silver layer FiA) is shown in FIG.

From FIG. 4, the main phase of the obtained high-temperature superconductor is a phase at 80, and a phase at 20 and a CuO peak are also observed. Furthermore, from FIG. 5, it can be seen that the resistance starts to drop around 90, and superconducting characteristics of Tc, zero = 73 K are obtained. No cracks were observed in this superconductor.

(Effects of the Invention) As detailed above, according to the present invention, it is possible to form a Bi-Sr-Ca-Cu-0-based oxide high-temperature superconducting film on copper substrates of various shapes. The practical benefits are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a triangular composition diagram of Bi-Sr-Ca based oxides. FIG. 2 is a diagram illustrating an example of the process of the method of the present invention, and FIG. 3 is a diagram showing an example of the structure of the oxide high temperature superconductor of the present invention. Figure 4 shows the XllA diffraction pattern of the copper-based Bi-based high-temperature superconducting composite obtained in the example, and Figure 5 shows the resistance curve of the copper-based Bi-based high-temperature superconducting composite obtained in the example. FIG. Patent applicant New Technology Development Corporation

Claims (6)

[Claims] (1) A metal base made of copper or copper alloy, and B on the base.
An oxide high temperature superconductor characterized in that an i-Sr-Ca-Cu-O-based oxide high temperature superconductor film is formed. (2) A metal substrate made of copper or a copper alloy, and a Bi-Sr-Ca-Cu-O based oxide high-temperature superconducting film formed on the substrate via copper oxide. High temperature superconductor. (3) The oxide high temperature superconductor according to claim 1 or 2, wherein the metal substrate is plate-shaped, tubular, or linear. (4) The oxide high temperature superconductor according to claim 1, 2 or 3, wherein the oxide high temperature superconductor film is formed entirely or partially on a metal substrate. (5) When manufacturing a Bi-Sr-Ca-Cu-O-based oxide high-temperature superconductor, formation occurs on or on the metal substrate at least the surface layer of which is made of copper or copper alloy. A Bi-Sr-Ca-based oxide is deposited on the copper oxide, which is then heat-treated in air, vacuum, or a reducing atmosphere to form a Bi-Sr-Ca-based oxide that integrates the oxide and Cu. A method for producing an oxide high-temperature superconductor, the method comprising obtaining a Sr-Ca-Cu-O-based oxide high-temperature superconductor film. (6) The Bi-Sr-Ca based oxide is Pb, S, B
The method according to claim 5, wherein the oxide is an oxide containing at least one of a and Te oxides.