JPH02183915A - Oxide superconducting compact - Google Patents

Abstract

PURPOSE:To obtain a superior superconducting characteristic by providing an oxide superconducting layer on either side of a base material via a noble metal layer or inorganic substance layer. CONSTITUTION:An oxide superconducting layer is provided on either side of a base material 3 via a noble metal layer 2 or an inorganic substance layer 4; or the superconducting layer 1 may be provided via both the noble metal layer 2 and the inorganic substance layer 4. Substances with a thermal expansion rate of 5 to 15X10<-4>/ deg.C should preferably be used as the base material 3. They include Ti, Zr, Ta, Nb, Fe, Ni, Co, Cr, Mo and their alloys. Other candidates include carbon, ceramics and crystals, such as MgO, SrTiO3, ZrO2 and Al2O3. Ag, Au, Pt, Pd and others are used for the noble metal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an oxide superconducting molded body used for wires, cables, printed circuit boards, electrical and electronic parts, and the like.

[Prior art and its section B] As oxide superconductors, Ba-Pb-B1 oxides that become superconducting at liquid He temperature are known, but in recent years, liquid H2 and Ne history have been developed at temperatures above N2 temperature. Oxide superconductors (hereinafter abbreviated as superconductors) that exhibit superconductivity have been developed. Examples of these superconductors include (L a XS r
I-X) ZCu 04 and YBa.

There is a composite oxide consisting of Cu, Group 3 elements such as OX, alkaline earth metals, and Cu, and its structure is KzN i
These are F4 structure and 0□-deficient layered perovskite structure. As a layered material with a similar Cu-0 plane structure,
B i -3r-Ca-Cu-0 system and T l -B a
-Ca-Cu-0 type materials are available, and those with higher critical temperatures (Tc) have been obtained.

The above-mentioned oxide superconductors are formed into conductors by making thick films by paste printing or the like, by making thin films by PVD or CVD, or by making wires, and their use in various applications has been attempted.

In all vapor phase methods such as the PVD method described above, film formation is performed in a vacuum, but when forming an oxide such as YBa2CulOX, 02 is insufficient due to side reactions such as decomposition reactions. A vacuum with a slight addition of □ is used, but it is difficult to maintain the optimal composition, and the film formed tends to be amorphous, and therefore has poor superconducting properties or does not exhibit superconducting properties at all. there were.

For this reason, conventionally after 11 days of acid, 9 times in an oxygen-containing atmosphere.
It is heated to around 00°C to adjust the composition of oxygen, etc. and the crystal structure, making it a superconductor.

By the way, the above-mentioned superconducting molded body is required to have the flexibility to withstand various mechanical and thermal stresses and strains in practical use and to be able to be molded into a desired shape. For example, superconducting molded bodies are cooled in a refrigerant such as liquid nitrogen during use, but are returned to room temperature when use is interrupted, so they are used under severe heat cycle conditions.

For this reason, a method of forming a superconductor into a film on a highly flexible substrate such as a metal is being considered. There is a problem in that the metal diffuses into the superconductor, degrading not only the critical current density (J, ) but also the superconducting properties such as the critical temperature (T c ) and the magnetic field (Hc).

During the above-mentioned heat treatment, there was a problem in that the constituent components of the superconductor segregated on the interface or surface, or in extreme cases, volatilized, making it impossible to obtain the desired superconducting properties.

Furthermore, when the superconductor film comes into contact with the outside air, there is a problem in that the superconducting properties rapidly deteriorate due to moisture and contaminant gas components in the atmosphere.

[Means and actions to solve the problem]

The present invention was made as a result of intensive studies in view of the above points, and its purpose is to reduce mechanical and thermal stress,
It is an object of the present invention to provide a superconducting molded body that is resistant to distortion, has excellent flexibility, and does not deteriorate over time.

That is, the present invention is characterized in that the oxide superconductor layer, in which the noble metal layer or the inorganic layer or both layers are sequentially provided on at least one side, is provided on both sides of the substrate with the noble metal layer or the inorganic layer on the substrate side. This is an oxide superconducting molded body.

As shown in the cross-sectional view of FIG. 1, the oxide superconducting molded body of the present invention has a noble metal layer 2 (FIG. 1a) or an inorganic layer 4 (FIG. 1b) on both sides of a base 3. As shown in the cross-sectional view of FIG. This is a typical structure.

The present invention is not limited to the above cross-sectional structure, but the second
．． As shown in FIG. 4, it is useful to interpose an inorganic layer 4 made of metal and/or non-metal between the noble metal layer 2 and the oxide superconductor layer 1.

In the present invention, the functions of the substrate vary depending on its use, but in most cases mechanical strength is the most important, and stabilizing effects such as electromagnetic stabilization are also important.

Metal is the most suitable material for the base material for electric wire and cable conductors because it not only has excellent flexibility and strength, but also can be obtained in long lengths stably and at low cost.

As for the characteristics required for the substrate, it is preferable that the thermal stress can be minimized during cooling and heating cycles, and materials with a coefficient of thermal expansion of 5 to 15 x 10-"/"C are advantageous, such as Ti, Zr, Ta, etc. ,,Nb,Fe,Ni,Cr,C
o, Mo, and alloys thereof. Of course, substrates made of composite materials such as Cu and Af, which have higher electrical conductivity and heat conductivity, are also useful.

The base material is made of carbon or 5rTi in addition to the above metal materials.
C) +, MgO5ZrO,, Aff, O! , Be01B
N, A/! A single crystal or polycrystal of ceramic such as N, or an amorphous inorganic layer such as Sin or multi-component glass is applied.

The shape of the substrate is generally a plate, a long tape, a wire, or the like.

In the present invention, the noble metal layer provided above the substrate or on the -F side of the superconductor layer includes Ag5Au and Pd.

PT, In, Os, Ru, Rh, etc. or alloys thereof are used.

In the present invention, the noble metal layer provided above the substrate acts as a barrier to prevent constituent elements of the substrate from entering the superconductor during heat treatment, and the noble metal layer provided above the superconductor layer acts as a barrier to prevent the constituent elements of the substrate from entering the superconductor during heat treatment. The layer suppresses the segregation and volatilization of the superconductor constituent elements that occur during heat treatment, and also prevents the
Superconductors can absorb moisture in the outside air, SO□, N08, H, S, (
It prevents rapid deterioration due to reaction with harmful gases such as l .

In the above, the thickness of the noble metal layer formed on the substrate is 0
．． The barrier effect is best developed at a thickness of 0.01 to 10 μm, particularly preferably 0.1 to 2 μm.

In the present invention, the inorganic layer provided in contact with the superconductor layer has the effect of controlling the growth of the superconductor layer and promoting oriented growth in a crystal orientation that maximizes the superconducting current.

In other words, as mentioned above, most oxide superconductors are layered materials, and superconducting current flows parallel to the Cu -0 plane perpendicular to the C-axis, so in many cases oriented growth with the C-axis perpendicular to the substrate occurs. It becomes necessary.

The inorganic substances that perform these actions are selected from the viewpoints of both crystal structure and chemical reactivity, and in particular, the following conditions must be met: ■ Low reactivity with superconductors; ■ Tetragonal, orthorhombic, and hexagonal crystals. It is necessary to satisfy the following requirements: , it is a crystal structure consisting of perovskite.

Among the above inorganic substances, non-metals include A2□01, Z"0□
,MgO1TiO,,5rTiOt,Sin,,B e
O, B a F t, BaZrOx, BaTi0. ,
Materials such as Bad, Cab, and SrO can be applied, and the thickness thereof is 0.018 m or more, particularly 0.05 to 2 μm.
It is practically useful in m.

In the present invention, it is also possible to use a metal for the inorganic layer, and a transition metal or an alloy thereof passes through the metal. The transition metal used in the present invention is an element belonging to Group 4.5.6 of the I11 table, and a particularly useful element is Ti.
, Zr, Cr, Mo, W, Nb, Ta, Fe, Ni, C
These are alloys such as O, N1-P series, N1-W-P series, Ni-Cu series, or Fe-Cr-Ni series of austenitic stainless steels.

In the present invention, the representative material of the superconductor layer is the above-mentioned (
LaS r), Cuba, YBa 2Cu 30x
sBiSrCaCuO11/! In addition to BaCaCuO, these substituents include Y S r o, 5B a 1.
5Cu zox, YosS Co, zB azcu, =
o, etc., all of which exhibit a perovskite structure. Also included are oxides in which part of O is replaced by an anion such as F, and part of CU is replaced by a cation such as Ag, Ni, or Fe.

The thickness of the superconductor layer is arbitrary, but it is 0.1 μm to 1 mm.
, particularly preferably 0.5 to 50 μm.

〔Example〕

The present invention will be explained in detail below using examples.

A noble metal layer, an inorganic layer, and a superconductor layer made of various materials were sequentially formed on both sides of a Hastelloy substrate or a 5O3304 substrate to produce an oxide superconductor molded body.

In the above, each layer is formed using a high frequency magnetron sputtering device, and the noble metal layer is formed in an Ar atmosphere (5
mTo r r), the inorganic layer is Ar+Ch atmosphere (
600 mTorr, 0.50%)
It was formed by heating to 'C.

In addition, the superconductor layer was placed in an Ar+O□ atmosphere (80 mTorr, 0
The substrate was heated to 650° C. and a load of 100 W was applied.

Further, the oxide superconducting molded body was subjected to heat treatment under various conditions as appropriate. After the heat treatment, it was cooled to 200°C at a rate of 2°C/min.

Regarding each oxide superconducting compact obtained in this way, the crystal orientation, critical temperature (Tc), critical current density (J
, ) were determined to be 1llll11.

The results are shown in Table 1 together with the material and manufacturing conditions for each layer.

As is clear from Table 1, the products of the present invention (Nos. 1 to 6) all exhibit high values of T and J.

This is mainly due to the effects of the noble metal layer of the product of the present invention suppressing the diffusion of the base metal element into the superconductor layer, and the inorganic layer controlling the growth of the superconductor and promoting oriented growth in the crystal orientation. This is due to

Among the products of the present invention, No. 6 has no intervening inorganic layer, so
The crystals of the superconductor layer were randomly oriented, resulting in a low value of J in the magnetic field.

Comparative product No. 7 has a too thin inorganic layer, so the effect is weak, and No. 8 has neither a noble metal layer nor an inorganic layer, so it is thought that the metal elements in the base diffused into the superconductor layer, resulting in a decrease in Jc.

〔Effect of the invention〕

As described above, in the oxide superconducting molded body of the present invention, since the noble metal layer is provided directly or via an inorganic layer on the side of the oxide superconductor that is in contact with the substrate, harmful elements can be prevented from entering from the substrate. At the same time, the crystal orientation of the superconductor is controlled, and therefore it exhibits excellent superconducting properties that reach a practical level, and has a significant industrial effect.

[Brief explanation of the drawing]

1 to 4 are cross-sectional explanatory views showing examples of the oxide superconducting molded body of the present invention. 1.--oxide superconductor layer, 2--noble metal layer, 3-.-substrate, 4.--inorganic layer, 5-.-noble metal layer. Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] An oxide superconductor characterized in that oxide superconductor layers are provided on both sides of a substrate with the noble metal layer or the inorganic layer facing the substrate, and at least a noble metal layer, an inorganic layer, or both layers are sequentially provided on one side of the oxide superconductor. Molded object.