JPH0465306A - Oxide superconductor thin film - Google Patents

Abstract

PURPOSE:To provide many centers capable of effectively pinning a magnetic flux and a high critical current density even in a strong magnetic field by forming the thin film having a structure in which the particulates of a multiple oxide consisting of specified metals are dispersed in an oxide superconductor crystal. CONSTITUTION:The oxide superconductor thin film has a structure in which the granular particulates of the multiple oxide of at least one kind selected from group IA elements and at least one kind selected from groups VIA and IVB elements and rare-earth elements are dispersed in an oxide superconductor crystal. The oxide expressed by the composition formula ABO3 (A is >=1 kind selected from Mg, Ca, Sr and Ba, and B is >=1 kind selected from Zr, Sn, Ce and Ti) is preferably used as the multiple oxide. The superconducting thin film can be produced by vapor deposition, sputtering, CVD or laser vapor deposition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oxide superconductor thin film having a novel structure.

[Prior art] Conventionally, RE-Ba-C:u-0 (RE is Y, La,
Nd, Sm, Eu, GdDy, Ho, Er,
one or more selected from the group consisting of Tm, Yb, and Lu) based superconductor (hereinafter also referred to as rare earth superconductor),
B1-3r-Ca-Cu-0-based superconductor (hereinafter also referred to as bismuth-based superconductor), Tl-Ba-Ca-Cu-0
Oxide superconductors such as thallium-based superconductors (hereinafter also referred to as thallium-based superconductors) are known.

As a method for manufacturing a thin film of an oxide superconductor, a method is known in which each element constituting the superconductor is deposited on a substrate using a vapor deposition method, a sputtering method, a CVD method, or a laser deposition method. It has been reported that by these methods, oriented polycrystals or single crystals can be obtained and superconductor thin films having high critical current density can be obtained.

[Problems to be Solved by the Invention] However, the oxide superconductor thin film obtained by the conventional method has a problem in that a strong current cannot flow under a magnetic field. This means that in superconductors,
It was thought that this was because there were not enough pinning centers to fix the penetrating quantized magnetic flux. It is an object of the present invention to provide an oxide superconductor thin film having a large number of effective pinning centers.

[Means for Solving the Problems] The present invention provides an oxide superconductor crystal containing at least one metal selected from Group 2A elements and at least one metal selected from Group 4A, Group 4B, and rare earth elements. The present invention provides an oxide superconductor thin film having a structure in which granular fine particles of a composite oxide with a metal are dispersed.

In the present invention, at least one selected from group 2A elements
The composite oxide of a seed metal and at least one metal selected from group 4A, group 4B and rare earth elements is ABO, (
It is preferable that A is one or more selected from Mg, Ca, Br, and Ba, and B is one or more selected from Zr, Sn, Ce, and Ti.

ABO3 becomes a crystal with a very stable perovskite structure. Both of these crystals have a temperature of 1200°C in the atmosphere.
It is a substance that is compositionally stable up to close range, and does not react with oxide superconductors during the thin film deposition process.

When ABO3 is used, the amount added is preferably 05 to 20 wt% based on the superconductor. Added amount is 0.5wt
If it is less than %, the effect of the addition will not be apparent, which is not preferable. If the amount added exceeds 20 wt%, the AXBOy phase will segregate in a part of the material, causing discontinuity in the superconductor, which is not preferable. More preferable A, BO
, is added in an amount of 2 to 10 wt%.

The particle size of the composite oxide particles is preferably 500 Å or less, since this increases the pinning effect. 200
It is even more preferable if it is less than Å.

The oxide superconductor thin film of the present invention can be manufactured by simultaneously vaporizing the composite oxide raw material and simultaneously depositing the composite oxide fine particles during the thin film deposition process.

The superconducting thin film of the present invention can be produced by vaporization method, sputtering method, C
It can be manufactured using either the VD method or the laser deposition method. In either method, the substrate is heated to 400 to 900°C.
It is preferable to deposit the material by heating it to . As a result, a thin film having a structure in which fine particles of a non-superconductor are dispersed in an oriented superconductor is obtained. After film formation, further heat treatment can be performed as necessary.

Various materials such as various heat-resistant alloys and ceramics can be suitably used as the material for the base body.

The oxide superconductor of the present invention is not particularly limited, and various materials such as rare earth-based, bismuth-based, thallium-based, etc. can be suitably applied.

When a rare earth superconductor is used as the oxide superconductor, Ba5nO, BaZr0. , BaTi0a,B
Since Ba-containing elements such as aCeO3 and BazSiOa are one of the constituent elements of superconductors, even if an element substitution reaction occurs, other alkaline earth elements do not substantially mix into the superconductor, so there is no adverse effect on superconducting properties. It is preferable because it does not give

[Examples] Example 1 Oxygen gas at I x 10-'Torr is introduced into a vacuum container. A nozzle was installed near the substrate so that the local oxygen pressure was I x 10-2 Torr. Y, Ba, and Cu were evaporated in a Knudsen cell at an atomic ratio of 12:3 or 12:4. Furthermore, the B component shown in Table 1 was evaporated using an electron beam Knudsen cell. Therefore, Ba and this B component react and ABO3
of fine particles were generated. The amount of evaporation of each component was controlled so that the content of ABO3 was 2 wt% with respect to the oxide superconductor. A (1,OO) single crystal of MgO was used as the substrate and heated to 650°C.

As a result, REBazCuJy or REJa4CusO
, a thin film in which 3 ABo particles were dispersed in the crystal was obtained.

The obtained thin film was patterned to a width of 500 LLm, and then the critical current density (77 K, 5 probes) at critical temperature and under a magnetic field was measured by a DC 4-terminal method.

The results are shown in Table 1.

Table 1 Comparative Example I YBa2Cu30y or YJa4C was deposited on the substrate in the same manner as in Example 1 except that the B component was not evaporated.
A thin film of ugOy was created. When measured in the same manner as in Example 1, YBa2Cu30y had a critical temperature of 86K and a critical current density (77K, 5T) of 1.000OA/cm.
For 2Y2Ba4CusOy, the critical temperature is 80K and the critical current density (77K, 5T) is 34.00OA/cm2.
Met.

Example 2 Two mixed gases of argon and oxygen (1=1) were placed in a vacuum container.
Introduce X 1O-2Torr. ABO3 and YBa
2Cu30. A thin film was created using the sputtering method using the sintered body as a target. Here, the A component of ABO3 was all Ba, and the B component shown in Table 2 was used.

A high frequency of 200 W and 50 W was applied to the ABO and YBazCuxOy targets, respectively, so that the content of ABO3 was 4 wt% with respect to the superconductor. A (100) single crystal of MgO was used as the substrate and heated to 650°C.

As a result, a superconductor thin film in which ABO3 particles were dispersed in YBa2CusOy crystals was obtained. Regarding this thin film, 5
After patterning to a width of 00 μm, the critical current density (77 K, 5
T) was determined. The results are shown in Table 2.

Table 2 Comparative Example 2 A thin film of YBa2Cu30y was formed on a substrate in the same manner as in Example 1 except that the AB[)3 target was not used. When measured in the same manner as in Example 1, the critical temperature was 83 K, and the critical current density (77 K, 5 T) was 90
00 A/cm2.

Example 3 A 1:1 mixture of argon and oxygen was placed in a vacuum container at 2
．． It was introduced at a pressure of 5×10−@Torr.

Bt□5raCaCu20. A film was formed by sputtering using the sintered body, ABO consisting of A and B shown in Table 2, and the sintered body as targets. High frequency BizSr
250 W and 70 Vv' were applied to the 2CaCuzOy target and ABO target, respectively, to remove ABO in the film.
, was controlled to be 2 wt%. The substrate is Mg0fl
OO) A single crystal was used and heated to 600°C. The obtained membrane was further treated in air at 850° C. for 2 hours.

This thin film was patterned to a width of 500 μm, and the critical temperature and critical current density at 77°C and 5 Tesla were measured by the DC four-terminal method. The results are shown in Table 3.

Table 3 Comparative Example 3 Same as Example 3 except that ABO was not used.
A Bi25rzCaCuaOy thin film was obtained. When measured in the same manner as in Example 1, the critical temperature of this thin film was 80°C, and the critical current density was 100OA/cm" (77K, 5
T).

Example 4 A 1:1 mixed gas of argon and oxygen was placed in a vacuum container, and 2
．． It was introduced at a pressure of 5 x 10-' Torr.

Film formation was performed by sputtering using the TIJazCa2Cu30y sintered body and the ABO3 sintered body consisting of A and B shown in Table 4 as targets. TIJaz high frequency
By applying 250 W and 50 W to the CaiCu30y target and AB○3 target, respectively, the ABO in the film was 2.
It was controlled to be wt%. The substrate is Mg0 (100)
A single crystal was used and heated to 600°C. The obtained membrane is
Furthermore T12Ba, zCuOy and T ], 20
The sample was placed in a crucible with S and treated in air at 900°C for 2 hours.

This thin film was patterned to a width of 500 μm, and the critical temperature and critical current density at 77°C and 5 Tesla were measured by the DC four-terminal method. The results are shown in Table 4.

Table 4 Comparative Example 4 Same as Example 3 except that ABO3 was not used.
A T1□BazCa2Cu30y thin film was obtained. When measured in the same manner as in Example 1, the critical temperature of this thin film was 11
At 8 K, the critical current density is 4000 A/c++12 (7
7K, 5T).

[Effects of the Invention] In the superconductor thin film of the present invention, non-superconductors are dispersed in the superconductor, and this acts as a center for good binding of magnetic flux, so that the critical current density is high even in a strong magnetic field.

Claims (1)

[Claims] 1. Composite oxidation of at least one metal selected from Group 2A elements and at least one metal selected from Group 4A, Group 4B, and rare earth elements in an oxide superconductor crystal. An oxide superconductor thin film with a structure in which granular particles are dispersed. 2. At least one metal selected from group 2A elements and 4
A composite oxide with at least one metal selected from group A, group 4B and rare earth elements is ABO_3, (A is Mg
, one or more selected from Ca, Br, and Ba, B is Zr,
2. The oxide superconductor thin film according to claim 1, wherein the oxide superconductor thin film is an oxide represented by a composition formula of one or more selected from Sn, Ce, and Ti. 3. The thin film production method is vapor deposition method, sputtering method, C
The oxide superconductor thin film according to claim 1 or 2, which is produced by a VD method or a laser evaporation method.