JPH01219017A - Production of oxide superconductor - Google Patents

Abstract

PURPOSE:To obtain an oxide superconductor having a dense, uniform crystal structure and high characteristics by bringing a compd. phase having a compsn. A1B3Cu2Ox (A is a group IIIa element and B is a group IIa element) and copper (oxide) into a diffusion reaction to form a superconductor having a compsn. A1B2Cu3O7-delta. CONSTITUTION:A copper layer 2 is formed on a base material 1 by plating, vapor deposition or other method. An oxide layer 3 having a compsn. Y1Ba3Cu2 Ox is formed on the layer 2, e.g., by mixing Y2O3 powder with BaCO3 powder and CuO powder in 1:3:2 ratio of Y:Ba:Cu, sintering and pulverizing the mixture and spreading the resulting powder. Heat treatment is then carried out to cause a diffusion reaction between the oxide layer 3 and copper or copper oxide diffused from the copper layer 2. By this reaction, an oxide superconducting layer 6 having a compsn. Y1Ba2Cu3O7-delta is formed and an oxide superconducting material A is obtd.

Description

[Detailed Description of the Invention] 1-Field of Industrial Application The present invention relates to oxides that are being developed for use in superconducting devices such as superconducting magnets used in nuclear magnetic resonance devices and particle accelerators, or for use in power transmission lines. The present invention relates to a method for manufacturing a superconductor.

"Prior Art" Recently, various oxide-based superconductors have been discovered whose critical temperature (Tc) for transitioning from a normal conductive state to a superconducting state exceeds the liquid nitrogen temperature.

This type of oxide superconductor can be used under much more advantageous cooling conditions than conventional alloy-based or intermetallic compound-based superconductors, which require cooling with liquid helium. It is being studied as a promising superconducting material.

Conventionally, as an example of a method for manufacturing a superconducting wire including such an oxide superconductor, a plurality of raw material powders containing each element constituting the oxide superconductor are mixed to prepare a mixed powder, and then this mixed powder is The powder is calcined to remove unnecessary components, and the calcined powder is filled into a metal tube and subjected to diameter reduction processing to obtain a wire rod of the desired diameter, which is then heat treated to compact the inside of the metal tube. A method for obtaining an oxide superconducting wire by causing a solid phase reaction in a body to produce an oxide superconductor is known.

``Problems to be Solved by the Invention'' However, in the conventional method described above, it is difficult to mix the raw material powders completely uniformly, so even if heat treatment is applied, the entire consolidated body does not become a completely uniform superconductor. In particular, when manufacturing long superconducting wires, there is a problem that it is not possible to obtain oxide superconducting wires with high critical current density because it is not possible to produce a superconductor with a uniform crystal structure over the entire length of the wire. there were.

In addition, the oxide superconductor formed inside the superconducting wire mentioned above is produced by sintering a compacted powder body and causing a solid phase reaction, and many powder particles are finely formed at the grain boundaries. The powder particles have a bonded structure with pores interposed between them, and current flows through the contact portions of the powder particles, so the critical current density is low.

Furthermore, when preparing a hot powder by mixing multiple raw material powders, it is difficult to uniformly disperse the elements constituting the oxide superconductor in the mixed powder, so the solid phase reaction during heat treatment is not uniform. There was a problem that a homogeneous oxide superconductor could not be produced. In addition, when fine pores are formed in the grain boundaries of an oxide superconductor, as in the case of planarity, cracks are likely to occur when stress is applied, and the mechanical strength is low, so it is difficult to manufacture superconducting magnets. Therefore, when coil processing is performed, cracks appear in the superconductor, resulting in a significant deterioration of superconducting properties.

The present invention has been made in view of the above problems, and provides a method for producing an oxide superconductor that can uniformly produce an oxide superconductor with no pores and a dense structure and has high mechanical strength. With the goal.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention solves the problems described above.
tcu30't-6 (A is Y, Sc, La,
Yb.

B represents one or more elements of the Ma group of the periodic table, such as E r, Eu, Ho, and Dy, and B represents one or more of the Ifa group elements of the periodic table, such as Ca, Sr, and Ba. ), A, B2C
This produces an oxide superconductor having a composition of LI307-6.

"Action" A + B t'c L due to the interdiffusion reaction between the oxide phase with the composition A IB yCuto X and copper or copper oxide
Is O? An oxide superconductor having a composition of -6 is produced.

In addition, since copper and oxygen are diffused into the oxide phase with the composition AlB5Cu1O) (to produce an oxide superconductor with the composition A IB *CLi2O7-6, the number of elements to be diffused is small, and the oxide phase Since the oxide superconductor is generated based on the , the diffusion reaction proceeds smoothly and reliably.

The present invention will be explained in more detail below.

1 to 5 show the manufacturing method of the present invention in Y-B a
This is for explaining an example applied to a method for manufacturing a -Cu-0 based oxide superconducting material.

In this example, first, melting point 80 of Ni, Zr, Ti, etc.
Pure metal at 0°C or higher, or Ni-Cu, Ti-A
A long tape-shaped base material l shown in FIG. 1 made of an alloy having a melting point of 800° C. or higher, such as I, N i-A 1, is prepared.

In addition, the base material! The shape may be tubular or linear.

Next, a copper layer 2 made of pure copper is formed on the outer surface of the base material 1 by a plating method, a vapor deposition method, a cladding method, or the like, as shown in FIG.

Next, on the outer surface of this copper layer 2, Y IB arc auto
An oxide layer 3 having a composition x is formed as shown in FIG. 3 to form a covering material 4.

To form an oxide having the composition Y IB asc auto X, for example, Y, 0. Powder and BaCO3 powder and C
Mix uO powder at a ratio of Y:Ba:Cu=1:3:2, and add 400 to 80% of this mixed powder as necessary.
A calcining process is performed to remove unnecessary components by heating to 0°C, and then sintering is performed by heating at 800 to 1100°C for several hours to several tens of hours in an oxidizing atmosphere such as the air or an oxygen stream. After drying, pulverization is carried out as many times as necessary. Next, this sintered powder is dissolved in a solvent such as ethanol containing an organic binder to form a slurry. Then, this slurry is applied to the outer surface of the copper layer 2 by a melt dipping method, a spraying method using a spray gun, a screen printing method using a screen printing machine, a doctor blade method, or the like to form an oxide layer 3. be able to.

Once the oxide layer 3 is formed, the coating material 4 is heated with Ar gas, H
Intermediate heat treatment is performed by heating to 400 to 700° C. in an inert gas atmosphere such as e-gas, N gas, or a vacuum atmosphere. By this intermediate heat treatment, the copper in the copper layer 2 and Ba contained in the oxide layer 3 interdiffuse, and the oxide layer 3
A layer called BaCuot is generated at the boundary between the copper layer 2 and the copper layer 2, and the copper in the copper layer 2 is diffused toward the oxide layer 3 side.

Next, it is heated to 800 to 1100°C for several hours to several hundred hours in an oxygen-existing atmosphere such as in an oxygen stream of 1 atm,
Thereafter, a final heat treatment is performed in which the material is slowly cooled down to room temperature at a rate of, for example, 100° C./hour.

Through this final heat treatment, the copper diffused from the copper layer 2 and the oxygen supplied from the heat treatment atmosphere and diffused become Y rBa
It diffuses into the oxide layer 3 having a composition of sCutoX and reacts. As a result, Y rB atc Li2O? An oxide superconductor having a composition of -δ is produced, a superconducting layer 6 shown in FIG. 4 is produced, and an oxide superconducting material (superconducting tape) A is obtained.

In addition, in the method described above, Y rB a3CL120
Copper and oxygen are caused to undergo a diffusion reaction with respect to the oxide layer 3 having a composition of x, so that Y rB azc usO? -6 is produced, and a small number of elements are diffused into the oxide layer 3 to produce Y rB atc 0
307-6 can be generated, which causes a diffusion reaction in a compacted body of mixed powder as in the past, and the diffusion of elements is much faster than when all the elements constituting the oxide superconductor are caused to undergo a diffusion reaction. is done easily and smoothly. Therefore, a dense oxide superconductor with a uniform crystal structure and no pores can be produced, and a superconducting material A with high critical temperature and high critical current density can be obtained.

In addition, in the oxide superconducting material A manufactured as described above, the elements undergo a mutual diffusion reaction between the copper layer 2 and the oxide layer 3 formed on the outside of the base material l, so that the superconducting layer 6
is generated, so the superconducting layer 6 is strongly adhered to other layers.

In addition, Ba contained in the oxide layer 3 due to intermediate heat treatment
Since the oxide superconducting layer 6 is generated after diffusing B aCuot to the copper layer 2 side to generate the layer BaCuot, the adhesion between the superconducting layer 6 and the base material 1 can be improved. Therefore, the superconducting layer 6 has good adhesion to the base material 1, and the superconducting material A has an excellent structure that is resistant to bending. Therefore, when superconducting material A is used for a superconducting magnet, the superconducting magnet can be formed by coil processing without causing defects such as cracks.

Moreover, the thickness of the superconducting layer 6 formed by heat treatment is
It can be controlled by adjusting the thickness of the copper layer 2 and the oxide layer 3, and the heat treatment temperature and time.

By the way, the superconducting material A can be used alone as a superconducting magnet coil or for power transport, but it is also possible to stack a large number of superconducting materials and store them inside a sheath to create a superconducting material for large-capacity fireflies. It can also be used as a conductor.

In addition, in the above-mentioned example, Y-B a-Cu-0
Although the method for manufacturing the A-B-Cu-0-based oxide superconducting material has been described, it goes without saying that the present invention can be applied to other methods for manufacturing A-B-Cu-0-based superconducting materials. Also, Y-B
When producing an oxide superconducting material other than the a-Cu-0 series, a different type of raw material powder is used to generate the oxide layer 3, and an element other than Ba is used as the Ila group element of the periodic table. Good. That is, when preparing raw material powder, Sc, Y, La,
Ce, Pr, Nd, Pi, Sm.

Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
Using one or more compound powders such as u, periodic table IIa
Group element compound powders include Sr, Mg, Ca, Ba
, Ra or the like may be used.

"Manufacturing Example" A copper layer with a thickness of 30 μm was formed on a Ni tape with a width of 2 mm and a thickness of 0 and 1 mm by a plating method using a sulfuric acid steel bath. In addition, Y t Oy powder and B a CO
3 powder CuO powder in molar ratio Y:Ba:Cu=1
:3 :2 ratio, heat treated in the atmosphere at 900° C. for 24 hours, and then pulverized twice to obtain a sintered powder.

Next, this sintered powder was dissolved in an organic solvent such as ethanol containing an organic binder to form a slurry, and this slurry was applied to the tape to form an oxide layer with a thickness of about 20 μm.

This tape was then heated at 600°C in an Ar gas atmosphere.
An intermediate heat treatment was performed in which the material was heated at 900° C. for 24 hours in an oxygen gas atmosphere of 1 atm, and then an oxide superconducting tape was obtained by slowly cooling it to room temperature.

This oxide superconducting tape showed a critical temperature of 92K, and was found to be an excellent oxide superconductor.

Further, when the cross section of the oxide superconducting tape was observed using an optical microscope, a reaction layer with a thickness of about 30 μm was confirmed. When this reaction layer was analyzed by X-ray diffraction, it was confirmed that it had a composition of Y IB at Cuto□-δ.

"Effects of the Invention" As explained above, the present invention diffuses copper and oxygen into the oxide phase of A1B3CUzOx to form A1B2Cu307-
It produces an oxide superconductor with a composition of 6,
Since oxide superconductors can be generated by diffusion of minority elements based on the oxide phase, elemental diffusion can be carried out smoothly and reliably, making it possible to create oxide superconductors with a dense and uniform crystal structure. It's effective if you can generate it.

Furthermore, since an oxide superconductor is generated by diffusing copper and oxygen into the oxide phase based on the oxide phase with the composition A IB 3Cu20 Compared to the case where all the elements constituting the oxide superconductor are caused to undergo a diffusion reaction, the number of diffusion elements is reduced, and the diffusion of the elements is facilitated and ensured. Therefore, it is possible to produce a dense oxide superconductor with a uniform crystal structure and no pores, and it is possible to obtain a superconducting material with high characteristics such as a high critical temperature and a high critical current density.

Furthermore, the oxide superconductor obtained by the present invention does not have the pores that are formed in oxide superconductors produced by conventional powder methods, so it has high mechanical strength and is resistant to bending stress. It becomes a strong structure. Therefore, the oxide superconductor produced by the method of the present invention does not produce cracks even when coiled to form a superconducting magnet, so it is possible to obtain a superconducting magnet with excellent superconducting properties. be.

[Brief explanation of the drawing]

Figures 1 to 4' are for explaining the present invention in detail. Figure 1 is a cross-sectional view of the base material, and Figure 2 is a cross-sectional view showing a state in which a copper layer is formed on the base material. , FIG. 3 is a sectional view showing a state in which a window and an oxide layer are formed on a base material, and FIG. 4 is a sectional view showing an oxide superconducting material. I... Base material, 2... Copper layer, 3... Oxide layer, 4...
...Covering material, 6...Oxide superconducting layer, A...Superconducting material. Outsourcer Fujikura Electric Cable Co., Ltd. Figure 1! Figure 2 Figure 3 Figure 4 Figure 8

Claims (1)

[Claims] General formula A_1B_2Cu_3O_7_-_δ (where A is Y, Sc, La, Yb, Er, Eu, Ho, Dy
B represents one or more elements of group IIIa of the periodic table, such as
It represents one or more elements of group IIa of the periodic table, such as a, Sr, and Ba. ) in the method for producing an oxide superconductor having the composition shown in A_1B_3Cu_2 in an oxygen-present atmosphere.
A method for producing an oxide-based superconductor, characterized in that an oxide superconductor having a composition of A_1B_2Cu_3O_7_-_δ is produced by a diffusion reaction between a compound phase having a composition of O_x and copper or copper oxide.