JPH0446055A - Oxide superconducting tape material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an RE-Ba-Cu-0 based oxide superconducting tape material having a novel structure.

[Conventional technology 1 Conventional RE-Ba-Cu-0 system has REBaiCumOy
It is known that there are crystals whose superconducting transition critical temperature (Tc) exceeds the liquid phoneme temperature, such as crystals, and attempts are being made to fabricate a wire by combining a metal substrate with a thick film containing these crystals as the main phase. For example, as a method of compounding a Y-Ba-Cu-0-based thick film with a metal substrate,
A method is to disperse calcined powder with the sCusOy composition in an organic solvent containing an acrylic binder and then apply it on a metal substrate and heat treat it to bake a thick film. Alternatively, a green sheet is prepared using a doctor blade method and then it is applied to the metal. There were methods such as printing it onto the board.

In such a method, by selecting an appropriate starting composition and firing conditions, a thick film can be partially melted on a metal substrate and then solidified. When such melt-solidification treatment is applied,
A dense thick film can be obtained, and the critical current density (Jc
) It has been reported in many cases that superconductor crystals may be oriented in a direction that allows for a large value.

[Problems to be Solved by the Invention] When a superconducting material is used in a strong magnetic field, it is required that the quantized magnetic flux penetrating the material be fixed at the center of the pin. Various defects such as microprecipitates, grain boundaries, and twin boundaries are considered to be the center of bottle fixation.

REBatCusO, phase (hereinafter referred to as 123 phase) does not form a uniform melt when heated and melted, and the REBatCusO phase (hereinafter referred to as 123 phase)
The CuOi crystal (hereinafter referred to as 211 phase) is decomposed and melted. Therefore, when a RE-Ba-Cu-0-based thick film is partially melted on a metal substrate, the 211 phase can be reduced to a certain degree by controlling the composition and heating conditions before melting the thick film.
It can be dispersed in three phases, resulting in a relatively high Jc.

It is thought that by finely dispersing these precipitates, the pinning force of the superconducting phase constituting the thick film is strengthened, and Jc is further improved. However, RE-B on a metal substrate
When the a-Cu-0 system is brought into a semi-molten state, the 211 phase tends to gather locally due to the surface tension of the liquid phase, and the 211 phase reacts with the liquid phase containing Ba and Cu during solidification.
Since a part of the 123 phase forms, it is difficult to achieve homogeneous dispersion of the 211 phase in a thick film on a metal substrate unless the amount and properties of the 211 phase and the melt in the melt zone are strictly controlled.

Does not react with any solid phase or liquid phase that exists in the semi-molten state of the RE-Ba-Cu-0 system, and RE-Ba-Cu
Melt 1wl of fine particles of non-superconducting substances that do not grow even at high temperatures where the -0 system becomes semi-molten! l! If the particles can be dispersed in the starting material before solidification and unidirectionally solidified on a metal substrate, then if a thick film material in which these particles are homogeneously dispersed in the 123 phase is prepared on the metal substrate, the homogeneous It is considered to be excellent for introducing mainly bottle fasteners.

[Means for solving the problems] The present invention has the following features. REBaiCumOy crystal (RE is Y,
La, Nd.

Sm Eu, Gcl, Dy, Ho, Er, Tm, Yb
, Lu, y is the amount of oxygen), 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 superconducting tape material characterized in that an oxide superconducting film having a structure in which granular crystals of a composite oxide with one or more metals are dispersed in an island shape is laminated with a metal.

In the present invention, at least one selected from group 2-A elements
As a composite oxide of at least one metal and at least one metal selected from group 4A, group 4B, and rare earth elements, ABO3 (A is Mg.

One or more selected from Ca, Sr, Ba, B is Zr
, Sn.

It is preferably represented by a compositional formula of one or more selected from Ce and Ti. AB obtained in this case
The O phase becomes a crystal with a very stable perovskite structure. All of these crystals are compositionally stable substances up to around 1200°C in the atmosphere, and are half of the thick film materials of the REBaxCulO system. ! At a temperature of 900 to 1100° C., it does not react with the RE-Ba-Cu-0-based melt, and hardly any grains grow. A.B.O.

In the case where A is Ba, it is particularly preferable because no divalent metal is introduced that may replace Ba in the 123 phase.

The oxide superconducting tape material of the present invention is preferably manufactured by the following method. For example, the composite oxide powder is mixed with a raw material mainly composed of 123 phase or a raw material having a composition of substantially 123 phase, such as 123 phase plus 211 phase or CuO, as a starting raw material. Then, an organic solvent, a binder, etc. are coated onto the substrate, or a green sheet is prepared by a doctor blade method or the like, and then the green sheet is bonded to the substrate and heat-treated.

The substrate is preferably a metal, and it is preferable to use a metal tape or foil because flexibility can be imparted to the superconductor tape material. The metal used here is not particularly limited as long as it has low reactivity with the molten superconductor. Specifically, silver, gold-palladium alloy, etc. are preferably used.

When a mixture of RE-Ba-Cu-0-based raw materials and the above composite oxide is heated above its melting temperature and then cooled to solidify, 123 phase crystals grow from the melt, and inside this The composite oxide crystals are taken in while maintaining the particle size added at the time of charging. Therefore, by using the above composite oxide in which only fine particles are selected, it is possible to disperse a non-superconducting substance of the same size in the superconducting phase, thereby increasing the binding force and allowing it to be used in a high magnetic field. This is preferable from the viewpoint of improving the superconducting properties of the superconducting tape wire.

When adding ABO, the amount added is preferably 0.5 wt% or more and 20 wt% or less based on the 123 phase. If the amount added is less than 0.5 wt%, the effect of the present invention may not be fully expressed, and if the amount added is less than 20 wt%, the effect of the present invention may not be sufficiently expressed.
If it exceeds wt%, ABOs crystals will segregate in a part of the material and inhibit the bonding between superconductors, which is not preferable. A more preferable amount of ABOa added is 1 to 10 wt%.

The thick film tape wire of the present invention has a temperature gradient of 50'C/cm.
As described above, it is preferable to manufacture the wire rod by unidirectionally solidifying the wire under the condition that the melting solidification rate is 50 mm/h or less.

As a result, a structure is obtained in which granular crystals of ABOI are dispersed in the form of islands in a matrix in which plate-shaped superconductor crystals oriented on a metal substrate are stacked in layers.

In the present invention, the raw material composition of the oxide superconductor is 123
When a phase composition closer to the 211 phase is adopted, a structure in which granular crystals of the 211 phase are uniformly dispersed in the 123 phase obtained by solidification is obtained. Since this 211 phase also acts as a center for pin fixing, the critical current density in the magnetic field is further improved. Further, from a melt having a composition closer to the 211 phase than the 123 phase composition, the 123 phase is stable and crystal growth is easy, so a structure with improved orientation of the 123 phase can be obtained. Therefore, characteristics such as critical current density are further improved.

[Example] Example 1 For the RE shown in Table 1, a calcined powder of oxide was prepared such that the atomic ratio of RE:Ba+Cu was 7:8:11,
In addition, ABO is a combination of A and B shown in Table 1.

3 wt % of powder (average particle size 0.5 μm) was added and mixed. An acrylic binder was added to this mixed powder, and a thick film green sheet with a thickness of 50 μm was prepared using a doctor blade method. In the system using both Y and Ho as RE, the Y:)to atomic ratio was set to 8:2.

When this green sheet was placed on a silver foil tape and baked in an oxygen stream at 920°C for 5 hours, REBa2Cu3
A structure was obtained in which the crystal grew with the a-b plane of the Oy crystal oriented parallel to the silver plane.

This tape material has a maximum temperature of 930℃ under an oxygen stream.
using an electric furnace with a temperature gradient of 50 °C/am at 2
When solidified unidirectionally in the longitudinal direction of the tape at a speed of mm/h, the REBaaCusOy crystals were found to be more strongly oriented.

By scanning and transmission electron microscopy, REBaiCu
When the microstructure inside the nOy crystal was observed, it was found that 211 phase granular crystals and an ABOg phase with almost no grain growth compared to the time of charging were uniformly dispersed inside the crystal.

The critical temperature of this silver substrate tape material was measured, and Jc at liquid nitrogen temperature (77 K) was further measured in a 1 Tesla magnetic field by the DC four-probe method. At this time, the magnetic field is
The voltage was applied parallel to the 123-phase C axis. The results are shown in Table 1.

Table Comparative Example I A superconductor tape was prepared in the same manner as in Example 1, except that a calcined powder of oxide was prepared such that the atomic ratio of Y: Ba: Cu was 7:8:11, and ABOs was not added thereafter. I got the material.

This superconductor had a critical temperature of 92°C.

The value of Jc in an applied magnetic field of 1 Tesla at a temperature of 77 is 5B.
It was OA/cm'.

Example 2 For the RE shown in Table 2, a calcined powder of oxide was prepared such that the atomic ratio of RE:Ba:Cu was 7:8:11.
To this was added 3 wt % of ABO3 powder (average particle size 0.5 μm) of the combination of A and B shown in Table 2 and mixed. An acrylic binder was added to this mixed powder, and a thick film green sheet with a thickness of 50 μm was prepared using a doctor blade method. In the system using both Y and HO as RE, the Y:Ho atomic ratio was set to 8=2.

This green sheet was placed on an alloy foil tape of 80% gold and 20% palladium and fired for 5 hours at 1000°C in an oxygen stream. A structure was obtained in which the crystal grew with the a-b plane of the REBaaCusOy crystal oriented parallel to the tape surface.

The tape material thus prepared was moved in the longitudinal direction of the tape at a speed of 10 mm/h using an electric furnace with a maximum temperature of 1020°C and a temperature gradient of 50°C/cm under an oxygen stream. It solidified. The REBaaCuaO crystals on the tape material after heat treatment were more strongly oriented.

By scanning and transmission electron microscopy, REBaaC+
When the microstructure inside the gOy crystal was observed, it was found that 211 phase granular crystals and an ABOs phase with almost no grain growth compared to the time of charging were uniformly dispersed inside the crystal.

Regarding this gold-palladium alloy substrate tape wire, as in Example 1, the critical temperature and liquid nitrogen temperature (77K),
Jc was measured in a 1 Tesla magnetic field. The results are shown in Table 2.

Table 2 Comparative Example 2 A superconductor was prepared in the same manner as in Example 5, except that a calcined powder of oxide with an atomic ratio of Y:Ba:Cu of 7:8:11 was prepared, and ABOs was not added thereafter. A tape wire rod was obtained.

This superconductor had a critical temperature of 92°C.

The JcO value at a temperature of 77 and in an applied magnetic field of 1 Tesla is 6.
80 A/cm".

[Effects of the Invention] In the superconductor tape wire of the present invention, non-superconductor crystal particles are dispersed in superconductor crystals.

Since this acts as a center for fixing the bottle, it exhibits a high critical current density even in a strong magnetic field.

Claims (3)

[Claims] 1. REBa_2Cu_3O_y crystal (RE is Y, L
a, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm
, Yb, and Lu (y is the amount of oxygen), at least one metal selected from group 2A elements and 4
An oxide superconducting film having a structure in which granular crystals of a composite oxide with at least one metal selected from Group A, Group 4B, and rare earth elements are dispersed in an island shape is laminated with a metal. oxide superconducting tape material. 2. A composite oxide 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 is ABO_3 (A is Mg, Ca, Sr, One or more types selected from Ba, B is Z
2. The oxide superconducting tape material according to claim 1, wherein the oxide superconducting tape material is one or more selected from r, Sn, Ce, and Ti. 3. The oxide superconducting tape material according to claim 1 or 2, wherein the REBa_2Cu_3O_y crystal is obtained by solidifying a melt.