JPH0446056A - Oxide superconductor 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 superconductor tape material having a novel structure.

[Prior art] Conventional RE-Ba-Cu-0 system has RE m Ba 4
It is known that the superconducting transition critical temperature (hereinafter referred to as Tc) exceeds the liquid nitrogen temperature, such as the Cu@Oy phase, and it is possible to fabricate a wire by combining a thick film containing these crystals as the main phase with a metal substrate. Attempts have been made to do so.

As a method for combining a Y-Ba-Cu-0-based thick film with a metal substrate, for example, a calcined powder having a composition of Y, Ba4Cu*Oy is dispersed in a bound solvent containing an acrylic binder, and then the film is deposited on a metal substrate. There were methods such as applying the green sheet to a metal substrate and baking it into a thick film through heat treatment, or using a doctor blade method to create a green sheet and then baking it onto a metal substrate.

In such a method, by selecting an appropriate starting composition and firing conditions, a thick film can be partially melted and then solidified on a metal substrate. When such melt-solidification treatment is applied,
It has been reported in many cases that superconductor crystals are oriented in a direction in which a dense thick film can be obtained and a high current density (hereinafter referred to as Jc) can be obtained.

[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.

The REJaiCu*Oy phase (hereinafter referred to as the 248 phase) does not form a uniform melt when heated and melted in an oxygen atmosphere of several atmospheres or more, and is first formed in a solid state by CuO+REBamCu.
It decomposes into Oy, and further decomposes and melts into REJaCuOs crystals (hereinafter referred to as 211 phase) and a melt at a high temperature. For this reason, RE
- When the Ba-Cu-0 system is partially melted on a metal substrate and then solidified, by controlling the composition and heating conditions before melting the thick film, the 211 phase or CuO phase can be reduced to a certain degree (248 phase). In this case, a relatively high Jc can be obtained.

By finely dispersing these compounds, the pinning force of the superconducting phase constituting the thick film is strengthened, and Jc is improved.

However, when the RE-Ba-Cu-0 system is brought into a semi-molten state on a metal substrate, the 211 phase tends to gather locally due to the surface tension of the liquid phase, and the 211 phase also
, reacts with the liquid phase containing Cu, and a part of it forms the 123 phase. Therefore, achieving homogeneous dispersion of the 211 phase in a thick film on a metal substrate requires the amount of the 211 phase and the melt in the melt zone. , is difficult unless the properties 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
If it is possible to disperse fine particles of a non-superconducting material that does not grow even at high temperatures such that the -a system becomes a semi-molten state into the starting material before melting and solidifying, and to solidify this unidirectionally on a metal substrate, 248 Preparing a thick film material on a metal substrate in which the particles are homogeneously dispersed in the phase is believed to be superior in introducing homogeneous bottled centers.

[Means for Solving the Problems] The present invention provides REJa4Cu@O, crystal (RE is Y, L
aNd Sm, Eu, Gd, Dy, Ha, Er, Tm
, Yb, Lu, y is the amount of oxygen), at least one metal selected from Group 2A elements, and Group 4A, Group 4B, and rare earth elements. An oxide superconductor tape material characterized in that an oxide superconductor film having a structure in which granular crystals of a composite oxide with at least one kind of metal are dispersed in an island shape is laminated with a metal. It is.

In the present invention, composite oxides 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 include ABO, (A is Mg, CaSr , B is preferably one or more selected from Zr, Sn, and CeTi). The helium-BOm phase obtained in this case becomes a crystal with a very stable perovskite structure. All of these crystals are compositionally stable substances up to around 1200℃ in the atmosphere.
At a temperature of 900 to 1100° C., which is the semi-melting temperature of the thick film wire of the REJa4Cua○ system, it does not react with the RE-Ba-Cu-0 system melt, and hardly any grains grow. ABO
When A in 3 is Ba, it is particularly preferable because no divalent metal is introduced that may replace Ba in the 248 phase.

The oxide superconductor tape material of the present invention is preferably manufactured as follows. For example, A
The powder of BO, is mixed and used as a starting material. An organic solvent, a binder, etc. are added to this and applied onto the substrate, or a green sheet is prepared by a doctor blade method or the like, and then bonded to the substrate and heat treated.

The REaBa4CuaOy crystal is preferable because the crystal becomes stable when a part of RE is replaced with Ca. It is preferable that approximately 1 to 40% of EIE be replaced with Ca.

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

When a mixture of the RE-Ba-CuJ raw material and the above composite oxide is heated above its melting temperature and then cooled and solidified, 248 phases grow as crystals from the melt, and when charged into the mixture, The composite oxide crystals are taken in while maintaining the added particle size. 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 ABOm, the amount added is preferably 0.5 wt% or more and 20 wt% or less relative to the 123 phase. If the added amount is less than 0.5 wt%, the effects of the present invention will not be sufficiently expressed. There is a risk, and the amount added is 20w.
If it exceeds t%, ABOs crystals will segregate in a part of the material and inhibit the bonding between superconductors, which is undesirable.The more preferable amount of ABO to be added is 1 to 10 wt%.

The thick film tape wire of the present invention has a temperature gradient of 50"C/am.
As mentioned above, it is preferable to manufacture the wire by unidirectionally solidifying the wire rod under conditions where the melt solidification rate is 50 am/h or less.
As a result, a structure is obtained in which granular crystals of ABOs are dispersed in the form of islands in a matrix in which plate-shaped superconductor crystals oriented on a metal base are stacked in layers.

[Example] Example 1 Regarding the RE shown in Table 1, a calcined powder of an oxide with an atomic ratio of RE:Ca:Ba:Cu of 4:1:10+20 was prepared, and the powder shown in Table 1 was added to the calcined powder. AB of the combination of ta^ and B
3 wt % of O3 powder (average particle size: 0.5 μm) was added and mixed. In Examples 3 and 4, the atomic ratio of Y:)to was 8:
It was set as 2.

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. When this green sheet was placed on a silver foil tape and baked in an oxygen stream at 920°C for 5 hours, RE
A structure was obtained in which the crystal grew with the a-b plane of the Ja4Cu*Oy crystal oriented parallel to the silver tape surface.

The maximum temperature of this tape material under an oxygen stream was 930°C.
2 m using an electric furnace with a temperature gradient of 50°C/cm.
When solidified unidirectionally in the longitudinal direction of the tape at a speed of m/h, the REIBa*Cu5Oy crystals were found to be more strongly oriented. REaBa4Cu by scanning and transmission electron microscopy
When the microstructure inside the -Oy crystal was observed, it was found that the ABO phase, with almost no grain growth compared to when it was charged, was uniformly distributed inside the crystal.

Regarding this silver substrate tape wire, Jc at critical temperature and liquid nitrogen temperature (77 K) was measured in a magnetic field of 1 Tesla by the DC four-terminal method. At this time, the magnetic field was applied parallel to the C axis of the 248 phase. The results are shown in Table 1.

Table 1 Comparative Example I Y: Ca: Ba: Cu atomic ratio is 4:1+
A silver substrate superconductor tape wire was obtained in the same manner as in Example 1, except that a calcined powder of oxide having a ratio of 10:20 was prepared and ABOs was not added. The critical temperature of this wire is 92, and the value of Jc in an applied magnetic field of 1 Tesla is 3.
It was 20A/cm'.

Example 2 Regarding the RE shown in Table 2, a calcined powder of an oxide with an atomic ratio of RE:Ca:Ba:Cu of 4:1:10:20 was prepared, and the A shown in Table 2 was added to the calcined powder. AB of the combination of and B
3 wt % of Os powder (average particle size: 0.5 μm) was added and mixed. In Examples 3 and 4, the atomic ratio of Y:Ho was 8
:2.

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. This green sheet was placed on an alloy foil tape of 80% gold and 20% palladium and fired for 5 hours in a 1000°C airflow, and the a-b plane of the REJa4Ctl*Oy crystal was oriented parallel to the tape surface. A crystal-grown structure was obtained.

By moving the tape material thus produced in the length direction of the tape at a speed of 10 o+m/h under an oxygen stream using an electric furnace with a maximum temperature of 1020°C and a temperature gradient of 50°C/cm. Solidified in one direction. The REJa4CusOy crystals on the tape after heat treatment were more strongly oriented. REJa4 by scanning and transmission electron microscopy
When the microstructure inside the CuaO crystal was observed, it was found that the ABO phase with almost no grain growth compared to when it was charged was uniformly dispersed inside the crystal.

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

Table 2 Comparative Example 2 The same procedure as Example 5 was made, except that a calcined powder of oxide was prepared with an atomic ratio of Y:Ca:Ba:Cu of 4:1:10:20, and ABO was not added. A gold-palladium alloy substrate superconductor tape wire was obtained in the same manner. The critical temperature of this wire was 92, and the value of Jc in an applied magnetic field of 1 Tesla was 880 A/c+a''.

[Effects of the Invention] The superconductor tape material of the present invention has non-superconductor crystal particles dispersed in the superconductor crystal, and these act as centers for fixing the bottle, so it can maintain a high critical current density even in a strong magnetic field. have

Claims (3)

[Claims] 1. RE_2Ba_4Cu_6O_y crystal (RE is Y
, La, Nd, Sm, Eu, Gd, Dy, Ho, Er,
one or more elements selected from the group consisting of Tm, Yb, and 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. An oxide superconductor tape material characterized in that an oxide superconductor film having a structure in which granular crystals of a composite oxide with at least one kind of metal are dispersed in an island shape is laminated with a metal. 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 superconductor tape material according to claim 1, wherein the oxide superconductor tape material is one or more selected from r, Sn, Ce, and Ti. 3. The oxide superconductor tape material according to claim 1 or 2, wherein the crystal containing RE_2Ba_4Cu_6O_y is obtained by solidifying a melt.