JPH0362421A - Manufacture of oxide superconductor laminated on substrate - Google Patents

Abstract

PURPOSE:To manufacture the lamination body of oxide superconductors while the oxide superconductors being strongly bonded to a substrate by keeping and baking a material turning into an oxide superconductor via a baking process in contact with the substrate having a copper or copper oxide layer on the surface thereof. CONSTITUTION:A suitable binder is added to the powder of a material turning into an oxide superconductor when subjected to a baking process, and slurry is thereby obtained. This slurry is formed into a sheet or tape shape and baked on a metal deposited with copper or copper oxide, thereby obtaining an oxide superconducting thick film strongly bonded on the metal. In order to obtain the aforesaid thick film, the slurry is molded by the doctor blade method. As a substrate laminated with the material turning into an oxide superconductor upon baking, it is possible to use a metal element, alloy, ceramic or the like without any specific limitation, if the material is not oxidized or deteriorated in the baking atmosphere, or does not lose superconducting characteristics due to reaction with an oxide superconductor. More concretely, silver or gold is used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a laminate of an oxide superconductor and other materials, and particularly relates to a method for manufacturing a laminate of a thick film oxide superconductor and metal foil. The present invention relates to a method of manufacturing a laminate having workability and deformability.

[Prior art] Since oxide superconductors are difficult to deform and have poor workability as they are, it has been proposed to combine them with other materials. For example, Singh et al.
Mixed and pulverized aCO5 was baked at 950°C for 24 hours to produce YBaiCumOt-y powder, which was then mixed with 13% silver powder, an appropriate binder was added, and formed into a tape using the doctor blade method. It is reported that this tape was then placed on a silver plate and baked in an oxygen atmosphere at 930 to 960°C to adhere it.

<Appl'.

Phys, Lett, 53 (3), 18 July
(198&)) However, according to the method of Singh et al., a large amount of silver powder is mixed in to bring YBaiCumOt-y into close contact with the silver plate, which has the problem of deteriorating the superconducting properties. In addition, this superconductor
It was relatively thick, about 400 μm, and it was difficult to bend it to a very large curvature.

[Problems to be Solved by the Invention] An object of the present invention is to firmly adhere to a substrate an oxide superconductor that does not contain a phase that deteriorates superconducting properties, such as the above-mentioned silver powder. The purpose is to obtain a laminate.

In particular, the aim is to form a thin oxide superconductor on a metal to obtain a flexible superconductor.

[Means for Solving the Problems] The present invention has been made to achieve the above-mentioned object, and includes a material that becomes an oxide superconductor by firing.
The present invention provides a method for producing an oxide superconductor laminated on a substrate, characterized in that the layer of copper or copper oxide is brought into contact with a substrate provided on the surface and fired.

In the present invention, since a layer of copper or copper oxide is provided between the substrate and the substance that becomes an oxide superconductor by firing, a laminate with high adhesive strength between the oxide superconductor and the substrate can be obtained. It will be done.

If the firing temperature is below the melting point of the substrate and above the temperature at which copper or copper oxide reacts with a substance that becomes an oxide superconductor by firing to form a liquid phase, copper or copper oxide becomes an oxide superconductor. It acts as a flux that lowers the melting point of the oxide superconductor when the superconductor is bonded to the substrate, allowing crystals of the oxide superconductor to melt and grow by precipitation at a temperature below the melting point of the substrate to be bonded. Therefore, it is preferable.

At this time, since the crystal C-plane is oriented on the substrate surface so as to be parallel to the substrate surface, not only the bonding strength is improved but also the characteristics of the superconductor are improved.

The reason why crystals are oriented is not necessarily clear, but it is thought to be influenced by the surface tension of the generated liquid phase or crystal growth due to dissolution and reprecipitation.

Various methods can be used to provide the copper or copper oxide layer, such as plating, vapor deposition, sputtering, CVD, and coating. By heating a previously provided copper layer in an oxidizing atmosphere, this can also be made into a copper oxide layer.

The thickness of the copper or copper oxide layer is preferably 1 to 50 μm.

Copper and copper oxide both have similar functions, but when copper is used, there is a risk that the copper itself will be oxidized during firing, depriving the surrounding area of oxygen and reducing the properties of the oxide superconductor. It is preferable to perform firing in a more strongly oxidizing atmosphere.

In the present invention, a substance that becomes an oxide superconductor by firing is a substance that can be substantially converted into an oxide superconductor by heating and firing, and is either an oxide superconductor itself or a substance that reacts during heating and firing. It is an unreacted precursor (hereinafter referred to as precursor) that produces an oxide superconductor phase, or a mixture thereof. It may contain components other than the oxide superconductor, and after firing, it may become an oxide superconductor with a small amount of non-superconducting phase dispersed inside. When using a substance containing a precursor, it is preferable because when the precursor reacts and becomes an oxide superconductor, it forms a strong bond with the metal and improves the adhesive strength of the laminate.

In addition to the oxide superconductor itself, substances that become an oxide superconductor by firing include, for example, oxides or carbonates of metal elements contained in the oxide superconductor in a desired atomic ratio. Mixed mixtures can be used. A complex oxide or complex salt containing multiple metal components can also be used. In addition, it is also possible to sinter the mixture of oxides, carbonates, etc. mentioned above at a temperature slightly lower than the temperature at which superconductors are formed, or for a time shorter than the time required for complete reaction even at the temperature at which superconductors are formed. A material in which an oxide superconductor phase is partially formed may also be used.

Furthermore, an oxide superconductor mixed with the above precursors can also be used.

In the present invention, the following method can be adopted to manufacture a laminate of oxide superconductors. For example, a method in which a powder of a substance that becomes an oxide superconductor when fired is shaped in advance, this molded body is placed on a substrate having a surface layer of copper or copper oxide, and then fired is a method in which the superconductor after firing is This is preferable because it becomes dense and strong. Specifically, a suitable binder is added to the powder of a substance that becomes an oxide superconductor when fired to form a slurry, which is then formed into a sheet or tape and placed on a metal coated with copper or copper oxide. By firing, a thick oxide superconductor film firmly adhered to the metal can be obtained. In order to obtain such a thick film, it is preferable to mold the slurry using a doctor blade method. A thick film of oxide superconductor can also be obtained by adding a suitable binder or solvent to the above powder, applying it to a substrate to which copper or copper oxide is attached, and then firing it.

A method in which an oxide superconductor is formed on a substrate to which copper or copper oxide is attached by a vapor phase method such as CVD and then fired can be similarly adopted.

In the present invention, the substrate to be laminated with the substance that becomes an oxide superconductor by firing must not change in quality by oxidation in the firing atmosphere, and must not react with the oxide superconductor and impair its superconducting properties. , single metals, alloys, ceramics, etc. can be used without particular limitation. Specifically, it is preferable to use silver or gold because it minimizes the contact resistance with the oxide superconductor and serves as a stabilizing material. It is preferable to use a thin metal plate as the base to laminate a thick film of oxide superconductor because it can be bent after firing. At this time, the thinner the thick film is, the smaller the radius of curvature can be bent. The thickness of the thick film is 300 μm or less, more preferably 100 μm
The following are preferred. Even if the oxide superconductor is formed into a thin film, a similarly flexible laminate can be obtained.

A coil or the like can be easily obtained by laminating a thick film of a superconductor on a thin metal plate coated with copper or copper oxide, cutting the laminated body into appropriate pieces, and winding the laminated body with a certain curvature. A superconducting wire can be obtained by coating a metal wire or inorganic fiber coated with copper or copper oxide with a powder of a substance that becomes an oxide superconductor when fired, and then firing.

In the present invention, the firing atmosphere is preferably an atmosphere containing oxygen, and when an unreacted precursor is used, the firing temperature and time are such that the unreacted portion can sufficiently react to produce an oxide superconductor. There is a need. Furthermore, it is preferable that the temperature conditions are such that the oxide superconductor grows on the surface of the substrate with its zero plane parallel to the surface of the substrate via the copper or copper oxide deposited on the substrate. That is, it is preferable that one isothermal surface is parallel to the substrate surface, a temperature gradient is provided so that the temperature is lower on the substrate, and during cooling, the liquid phase generated during firing is solidified from the substrate. When firing while moving the substrate using a heating device with a temperature gradient parallel to the surface of the substrate using the zone melting method,
This is preferable because the crystal orientation is further improved.

The manufacturing method of the present invention is applicable to Y regardless of the composition of the oxide superconductor.
-Ba-Cu-0 system, Bi (Pb) -Ca-3r-
It can be applied to any of the Cu-0 system, Tl-Ba-Ca-Cu-0 system, etc.

[Example] Example I Y*Oi, BaCO5, and CuO powders mixed so that the molar ratio of Y: Ba: Cu was 1:2:3 were fired at 850°C for 5 hours to obtain a pre-fired powder. Ta. An acrylic binder was added to this powder, and a green sheet with a thickness of 50 μm was formed using a doctor blade method.

This is electroplated with 8 μm thick copper to a thickness of 120 μm.
It was placed on silver foil and baked in an oxygen stream at 950°C for 5 hours.

The resulting laminate did not crack even when it was wound around a cylinder with a diameter of 3 mm, and no change in appearance such as peeling occurred even when it was put in and taken out of liquid nitrogen. When measured using the DC four terminal method, the critical current density at liquid nitrogen temperature was 4000 A/cm.According to the observation of the cross section and surface using a scanning electron microscope, this oxide superconductor was formed on a silver plate. It had an oriented structure in which the 0 plane was aligned parallel to the plate surface.

Comparative Example 1 A laminate was obtained in the same manner as in Example 1 except that silver foil without copper plating was used. In this laminate, the crystals of the oxide superconductor were unoriented, and the critical current density at liquid nitrogen temperature was 1200 A/cm''.

Example 2 The green sheet of Example 1 was placed on a 120 μm thick gold foil prepared by electroplating copper with a thickness of 12 μm and fired. Maximum temperature is 965℃, temperature gradient is 100℃/c
Solidification occurred in one direction from the substrate side using a temperature gradient furnace.

The resulting laminate had a single-crystalline structure with higher zero-plane orientation and larger crystal grain size than the laminate of Example 1. The critical current density at liquid nitrogen temperature is
It was 13000A/c-.

Example 3 Bi:Pb:Ca:Sr:Cu molar ratio is 2:0.3
BIJx, Pt so that the ratio is 5: 2: 2: 3
)0. Mix CaCO3,5rCO3CuO powder,
An acrylic binder was added and a green sheet with a thickness of 200 μm was formed by a doctor blade method. Separately, a 120 μm thick silver foil prepared by electroplating 10 μm thick copper was fired in the atmosphere at 500° C. for 3 hours to produce a silver foil having a copper oxide layer on the surface. The above green sheet was placed on this silver foil and baked at 845° C. in air for 2 hours to obtain a laminate.

The resulting laminate did not crack even when it was wound around a cylinder with a diameter of 5 mm, and no change in appearance such as peeling occurred even when it was put in and taken out of liquid nitrogen. The critical current density at liquid nitrogen temperature was 3000 A/cm'' when measured by a DC 4-probe method.

[Effects] According to the present invention, a laminate in which an oxide superconductor is firmly adhered to a substrate can be obtained. Further, in this laminate, the crystals of the oxide superconductor have improved orientation, so properties such as critical current density are improved.

If firing is performed under a temperature gradient, the oxide superconductor will have a structure close to that of a single crystal, and its properties will be further improved.

When a thin oxide superconductor is baked onto a thin metal, it can be easily cut or bent, so tapes, coils, wires, etc. can be easily obtained. It is also possible to manufacture large-area thin plates for magnetic shielding.

Claims (11)

[Claims] (1) A method for manufacturing an oxide superconductor laminated on a substrate, characterized in that a substance that becomes an oxide superconductor upon firing is brought into contact with a substrate on which a layer of copper or copper oxide is provided and fired. . (2) The manufacturing method according to claim 1, wherein a molded powder that becomes an oxide superconductor by firing is brought into contact with the substrate. (3) The manufacturing method according to claim 2, wherein the powder that becomes an oxide superconductor by firing is formed into a thick film. (4) Claim 3, in which the molding is performed by a doctor blade method.
manufacturing method. (5) The manufacturing method according to claim 1, wherein a mixture obtained by adding a binder to a powder that becomes an oxide superconductor by firing is brought into contact with the substrate by coating. (6) The manufacturing method according to any one of claims 1 to 5, wherein the substance that becomes an oxide superconductor upon firing contains a precursor of an oxide superconductor. (7) Any one of claims 1 to 6, wherein the substrate is silver or gold.
manufacturing method. (8) The manufacturing method according to any one of claims 1 to 7, wherein the substrate is a thin plate. (9) The firing temperature is below the melting point of the substrate and above the temperature at which copper or copper oxide reacts with a substance that becomes an oxide superconductor upon firing to form a liquid phase.
Any one of the manufacturing methods. (10) Claim 9: During cooling, when the liquid phase solidifies, a temperature gradient is created perpendicular to the surface of the substrate so that solidification proceeds from the substrate side.
manufacturing method. (11) A coil member obtained by processing a laminate obtained by the manufacturing method according to any one of claims 1 to 10.