JPH02207414A - Oxide superconducting wire - Google Patents

Abstract

PURPOSE:To obtain an oxide superconducting wire with excellent superconductive property by forming an oxide superconducting layer on the base material of yttria stabilized zirconia which has flexibility and Al impurity amount specified to restrain diffusion reaction. CONSTITUTION:An oxide superconducting layer is formed on the base material of yttria stabilized zirconia which has an Al impurity concentration of less than 0.1wt.%, preferably less than 0.05wt.%, and flexibility to obtain an oxide superconducting wire. In this manner, diffusion reaction on Al included in yttria stabilized zirconia is restrained to permit less decrease in superconductivity, especially critical temperature, critical current density, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an oxide superconducting wire that can be used for superconducting coils, superconducting cables, and the like.

[Prior Art] Metal-based, compound-based, and ceramic-based superconductors have been known as superconductors, and their applications to various uses are being studied.

In other words, when a superconductor is kept at a temperature below its critical temperature, its electrical resistance becomes zero, and this property can be used to generate high magnetic fields, transmit large amounts of current at high density, etc. is being attempted.

Recently, ceramic-based materials have been attracting attention as superconducting materials because they can raise the critical temperature at which superconductivity occurs. Such superconducting materials can be used for power transmission and distribution, electrical connections between various devices or elements, alternating current windings, and the like by forming elongated linear bodies, for example.

Conventional methods for turning ceramic-based superconducting materials, that is, oxide-based superconducting materials, into wire rods include filling a metal vibrator with oxide superconductor powder and processing it to reduce its area, or using a long base material. A method is known in which a layer of oxide superconducting material is formed on a material to form a wire. A superconducting wire in which an oxide superconductor layer is formed on an oxide single crystal fiber is disclosed in, for example, Japanese Patent Laid-Open No. 63-271816. As a method for forming the oxide superconducting layer, vapor phase thin film forming methods such as vapor deposition, sputtering, and CVD can be applied.

[Problems to be Solved by the Invention] However, in order to obtain a high critical current density in such a superconducting wire, it is usually necessary to perform high heat treatment. MgO and S r that provide a film with excellent crystallinity
Even when forming an oxide superconductor layer on a single crystal such as TiOs, the substrate temperature during film formation must be kept at 600 to 700°C.
Therefore, it is necessary to further perform heat treatment at a temperature of 900° C. or higher after film formation.

When an oxide superconductor layer is formed on a flexible substrate of metal, ceramic, glass, etc., the crystallinity is poor and heat treatment at a higher temperature and for a longer time is required. However, when such a high temperature and long time heat treatment is performed, a diffusion reaction occurs with the substrate, and the superconducting properties of the formed oxide superconductor layer deteriorate. In order to prevent such a diffusion reaction, it is possible to form an intermediate layer between the substrate and the oxide superconductor layer, but in order to withstand long-term heat treatment at high temperatures,
A thick intermediate layer of 1 μm or more is required, which increases the cost for forming the intermediate layer.

An object of the present invention is to solve these conventional problems and provide an oxide superconducting wire that is less affected by diffusion reactions and has excellent superconducting properties.

[Means for Solving the Problems] The oxide superconducting wire of the present invention has flexibility and
The present invention is characterized in that an oxide superconducting layer is formed on an yttria-stabilized zirconia base layer containing less than 0.1% by weight of impurities.

In this invention, the amount of Am impurities in the yttria-stabilized zirconia used as the base material is less than 0.1% by weight, more preferably less than 0.05% by weight. In this specification, the amount of impurity A refers to the amount of impurity as A'120a.

[Function] In this invention, the amount of Al impurities in the yttria-stabilized zirconia used as the base material is set to less than 0.1% by weight because Afi is the most easily diffused among the impurities contained in the yttria-stabilized zirconia. This is because by reducing this diffusion reaction of All, it is possible to suppress a reduction in superconducting properties, particularly in critical temperature (Tc).

In particular, when a YBaCuO-based oxide superconducting layer is formed on an yttria-stabilized zirconia base material containing 0.1% by weight or more of Al impurities, Y2Ba, Cu10. It is easy to form oxides with a composition of The presence of oxides of this composition reduces superconducting properties such as critical temperature (Tc) and critical current density (Jc). In this invention, when the amount of Al impurities is 0.1% by weight or more, Y2 BaI Cut
This was achieved by discovering the phenomenon of easy formation of different phases such as o.

[Example] Thickness 0 with different An impurity concentrations as shown in Table 1
．． A Y-Ba-Cu-0 based oxide superconducting layer was formed on a 1 mm tape-like body of yttria-stabilized zirconia (Y content: 3% by weight) by RF magnetron sputtering. The film forming conditions are as follows.

Target: Y, Ba2 Cu3,10x Target diameter: 100 mm Substrate temperature: 680°C RF power: 100 Watts Gas pressure: 50 mTorr Oxygen partial pressure (02/ (02+Ar)): 50% Target-substrate distance: 45 mm Film formation time = 6-hour film thickness: 0.8 to 1.2 μm After forming the oxide superconducting layer as described above, heat treatment was performed at 950° C. for 0.5 hours in oxygen.

For each oxide superconducting layer, the critical current density (Tc) at which the resistance R becomes 0 was measured and shown in Table 1.

(Margin below) table The cross-sectional shape of is not particularly limited.

[Effects of the Invention] As explained above, the oxide superconducting wire of the present invention has the following properties:
An oxide superconducting layer is formed on a base material of yttria-stabilized zirconia containing less than 0.1% by weight of Ai impurities.

In this way, with this invention, A! Since a base material with a low content of L is used, diffusion reactions during heat treatment can be suppressed, and deterioration in superconducting properties due to heat treatment can be reduced.

As is clear from Table 1, Examples 1 to 5 according to the present invention
Although the oxide superconducting layer showed a high Tc, Comparative Examples 1 to 3, which had a larger amount of impurities than the range of the present invention, had a significantly lower Tc than Examples 1 to 5.

Claims (2)

[Claims] (1) Flexibility and Al impurity content of 0.1% by weight
1. An oxide superconducting wire, characterized in that an oxide superconducting layer is formed on a base material of yttria-stabilized zirconia having a yttria-stabilized zirconia. (2) The oxide superconducting wire according to claim 1, characterized in that the amount of Al impurities is less than 0.05% by weight.