JPH01219018A - Production of oxide superconducting material - Google Patents

Abstract

PURPOSE:To obtain an oxide superconducting material having a dense, uniform crystal structure and high characteristics by forming a porous oxide layer having a compsn. A2B1Cu1O5 (A is a group IIIa element and B is a group IIa element) on the outside of a core material made of a metal, impregnating a molten B-Cu alloy and carrying out heat treatment. CONSTITUTION:Y2O3 powder is mixed with BaCO3 powder and CuO powder in 2:1:1 ratio of Y:Ba:Cu and the mixture is sintered and pulverized. The resulting powder is mixed with a binder and spread on a core material 1 made of a metal. The binder is then removed by heat treatment to form a porous oxide layer 2 having a compsn. Y2Ba1Cu1O and to produce a coated material 3. This material 3 is immersed in a molten Ba-Cu alloy and a composite material 7 is produced by filling the molten Ba-Cu alloy into the pores in the layer 2. An oxide superconducting layer 9 is formed by heat-treating the material 7 in an atmosphere contg. oxygen and an oxide superconducting material A is obtd.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention was developed as a winding wire for a superconducting magnet used in superconducting application equipment such as a nuclear magnetic resonance apparatus or a particle accelerator, or as a power transport line. The present invention relates to a method for producing oxide superconducting materials, which is currently being developed.

``Prior Art J'' Recently, various oxide-based superconductors have been discovered whose critical temperature for transitioning from a normal conducting state to a superconducting state exceeds the temperature of liquid nitrogen.

Conventionally, as an example of a method for manufacturing a superconducting wire comprising this type of oxide superconductor, a mixed powder is prepared by mixing a plurality of raw material powders containing elements constituting the oxide superconductor, and the 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, and after the diameter reduction processing, heat treatment is performed in an oxygen atmosphere to solidify the compacted powder inside. A method of manufacturing an oxide superconducting wire by causing a phase reaction to generate an oxide superconductor is known.

"Problems to be Solved by the Invention" However, in the case of oxide superconducting wires manufactured by the conventional method described above, the oxide superconductor is produced by causing a solid phase reaction in the compact obtained by compacting the powder. Since the oxide superconductor is produced, it has the disadvantage that fine pores exist inside the produced oxide superconductor. In other words, such an oxide superconductor has a structure in which a large number of powder particles are joined together, and has fine pores at the grain boundaries, so that current flows through the contact portions of the powder particles. There was a problem that superconducting properties such as critical current density were inferior. In addition, when preparing a mixed powder by mixing multiple raw material powders, it is difficult to uniformly disperse the elements that make up the oxide superconductor within the mixed powder, so it is difficult to uniformly disperse the solid phase reaction during heat treatment. There was a problem that a homogeneous oxide superconductor could not be produced. In addition, the conventional oxide superconductor has the disadvantage of low mechanical strength because of the formation of fine pores in the grain boundaries, and cracks are likely to occur when coil processing is performed to manufacture superconducting magnets. There was a problem.

The present invention has been made to solve the above problems,
It is possible to produce dense and uniform oxide superconductors,
The object of the present invention is to provide a method that can produce an oxide superconducting material that is easy to form into a wire and has a high critical temperature and high critical current density.

"Means for Solving the Problems" The present invention is based on the general formula A-B-Cu-0 (where A is
Periodic table 11111 including Sc, Y, La, Ho, Er, etc.
B represents one or more elements of group a, and B represents one or more elements of group IIa of the periodic table, such as Sr and Ba. ), a porous oxide layer having a composition of A2B and CuOs is formed on the outer periphery of a metal core material to form a coating material. Next, this coating material is immersed in a B-Cu alloy molten metal to impregnate the pores of the oxide layer with the B-Cu alloy molten metal to create a composite material, and then this composite material is heat treated in an oxygen-containing atmosphere. The solution to this problem was to generate an oxide superconductor by

"Action" A t B + Cu r 05 formed on the outside of the core material
By impregnating a porous oxide layer with a composition as follows with a molten B-Cu alloy and subjecting it to heat treatment, the constituent elements of the oxide layer and the constituent elements of the molten alloy undergo a diffusion reaction to produce an oxide superconductor. Note that, based on a porous oxide layer with a composition of A x B r Cu lOs, an oxide superconducting layer is generated by diffusing elements of a molten B-Cu alloy that is uniformly impregnated throughout the oxide layer. This facilitates and uniformly diffuses the elements, producing an oxide superconductor with a dense and homogeneous structure. In addition, long oxide superconducting materials can be continuously produced by using a long core material, forming an oxide layer on this core material, and continuously supplying this to the molten metal and performing heat treatment. Ru.

The present invention will be explained in more detail below.

1 to 5 illustrate the present invention in Y-B a-Cu-
This is to explain an example applied to a method for manufacturing a 0-based oxide superconducting material. Prepare. This base material I has Ni, Zr.

Pure metal with a melting point of 800℃ such as Ti, or N1-C
Melting point of uST i-A 1, N i-A 1, etc. 80
It is a tape-shaped material made of an alloy with a temperature of 0°C or higher. In this example, the base material I is tape-shaped, but the base material 1 may be formed into a linear shape, a tubular shape, or the like.

Next, Y t is applied to the outer surface of this base material 1 as shown in FIG.
A porous oxide layer 2 having a composition of B a+ OLll Os is formed. This oxide layer 2 can be formed, for example, by the method described below.

First, Y compound powder such as Y, 03 powder or Y alloy powder, Ba compound powder such as BaCO3 powder or Ba alloy powder, and copper oxide powder such as CuO powder are mixed into Y:Ba:Cu=2: l:1 ratio, and after calcining this mixed powder as necessary, heat it at 800 to 1100°C for several hours to several tens of hours in an oxygen-rich atmosphere such as the air or an oxygen stream. The sintered body is pulverized to obtain a sintered powder. Next, this sintered powder is dissolved in a mixed solvent such as ethanol and an organic binder to obtain a slurry. Then, this slurry is applied to the outer periphery of the core material 1 by a spraying method using a spray gun, a printing method using a screen printer, a doctor blade method, or the like. Then Ar gas, N.

The binder in the coating layer is removed by heat treatment at 600 to 800° C. for several hours to several tens of hours in an inert gas atmosphere such as gas or a vacuum atmosphere.

Through this treatment, a porous oxide layer 2 as shown in FIG. 2 can be formed and a coating material 3 can be obtained. Note that, since this oxide layer 2 is impregnated with a molten alloy as described later, it is preferable that the porosity thereof be in the range of 40% to 60%. If the porosity is greater than 60%, the porous layer becomes brittle and peels off during immersion, which is undesirable. If the porosity is less than 40%, penetration of the molten metal becomes insufficient, which is undesirable. Note that the oxide layer 2
After forming the coating material 3, the coating material 3 is heated to 800 to 90% in an inert gas atmosphere such as N or gas atmosphere or in a vacuum atmosphere.
Oxide layer 2 and base material 1 are heated at 50°C for several hours to several tens of hours.
It is preferable to improve the adhesion of.

Next, this coating material 3 is coated with B a- using the apparatus shown in FIG.
Immerse in molten Cu alloy. The apparatus shown in FIG.
- It is mainly composed of a bathtub 5 filled with molten Cu alloy Y, and conveying rollers 6 for guiding the coating material 3 into the bathtub 5. Note that, outside the bathtub 5, there is a device (
(Illustrated path) is installed.

In addition, the concentration of Ba in the Ba-Cu alloy molten Y is 40at
% or less is preferable.

When the coating material 3 is introduced into the bathtub 5 using the transport rollers 6 and immersed in the molten metal Y, the pores inside the oxide layer 2 are impregnated with the molten metal Y. Here, the conveyance roller 6...
When the coating material 3 is drawn out from the molten metal Y at a predetermined speed by adjusting the rotational speed of the oxide layer 2, the solidified body of the Ba-Cu alloy molten metal Y is impregnated into the pores inside the oxide layer 2, as shown in FIG. A composite material 7 having a similar structure is obtained.

Next, this composite material 7 is subjected to a heat treatment in which it is heated at 800 to 1100° C. for several hours to several tens of hours in the air or in an oxygen-present atmosphere such as an oxygen gas stream atmosphere, and then slowly cooled.

Through such heat treatment, the constituent elements of the oxide layer 2 having a composition of YtBa+Cu+Os and the constituent elements of the B a-Cu alloy molten Y undergo a diffusion reaction, resulting in Y IB at Cu30 t
A superconducting layer 9 shown in FIG. 5 made of an oxide superconductor having a composition of -8 is produced, and an oxide superconducting material A can be obtained. In addition, in the above-mentioned heat treatment, the heating temperature was 850°C.
The temperature is preferably 950° C. to 950° C. Heating in this temperature range can prevent the crystal grains of the oxide superconductor from becoming coarser and produce an oxide superconductor with fine crystal grains.

In addition, when cooling after heat treatment, in order to transform the crystal structure of the oxide superconductor into an orthorhombic crystal,
It is preferable to cool slowly in the temperature range of 400°C, so if the temperature reaches 400°C or lower, rapid cooling may be used.

In the above case, an oxide layer 2 having a composition of A tB ICLll Os and a Ba-
Since the oxide superconductor is generated by interdiffusion reaction based on the elements of the molten Cu alloy Y, a uniform diffusion reaction can occur throughout the oxide layer 2. For this reason, the diffusion reaction of the elements is more uniform and smoother than in the conventional case where an oxide superconductor is produced by subjecting a powder compact to a solid phase reaction, and a homogeneous oxide superconductor with a dense structure is produced. . Therefore, an oxide superconducting material A having excellent superconducting properties such as critical temperature and critical current density can be obtained. Furthermore, since the porous oxide layer 2 formed on the outer periphery of the core material 1 is impregnated with the molten alloy, it is possible to generate the oxide superconductor 9 with a desired thickness depending on the thickness of the oxide layer 2. This has the effect of making it possible to easily manufacture a superconducting material having an oxide superconductor 9 of sufficient thickness.

By the way, in the above example, an example was explained in which the method of the present invention was applied to a Y-B a-Cu-0 series superconducting material, but other types of oxide superconducting materials included in the A-B-Cu-0 series Of course, the present invention can be applied to the manufacturing method of.

That is, in the A-B-Cu-0 system, as the A element,
Sc, Y, La, Ce, Pr, Nd, Pm instead of Y
, Sm.

Eu, Gd, Tb, Dy, Ho, Er, Tm, 'Yb,
The present invention may be carried out by selecting one or more elements from group 111a elements of the periodic table such as Lu, Mg, Ca, Sr, C
The present invention may be carried out by selecting one or more elements from group IIa elements of the periodic table such as a.

"Example" Y t B a + Cu t O with a thickness of approximately 20 μm on a tape made of Ni and having a width of 2 mm 5 and a thickness of O, l mm.
An oxide layer having a composition of s was formed. To form this oxide layer, particle size -325 mesh (average particle size 40 μm)
A slurry in which oxide powder having a composition of Y 2B a, Cu, and O is dispersed in a mixed solvent of an organic binder and ethanol is applied to the outer periphery of the core material, and then N is applied.

It was formed by heating at 300° C. for 3 hours in a gas atmosphere to remove the organic binder. Note that the tape material was further heated at 950° C. for 48 hours in a N2 gas atmosphere to improve the adhesion between the oxide layer and the base material. In this state, a part of the oxide layer is cut out and its porosity is
It was measured to be about 45%.

Subsequently, Cu-30Ba (at%) alloy was melted using a CaO crucible in an Ar gas atmosphere to create a molten alloy, and the temperature of this molten metal was maintained at about 950°C. Then, about 50% of the tape material on which the oxide layer was formed was added to the molten metal.
It was passed at a speed of m/min.

Through this operation, the pores of the oxide layer were impregnated with the molten Cu and -Ba alloy to obtain a composite material. When we cut out a part of this composite material and measured the porosity of the oxide layer, the porosity was approximately 5.
%.

Next, this composite material was placed in an oxygen flow atmosphere of 1 atm.
A heat treatment of heating at 920° C. for 12 hours and then slow cooling was performed to obtain an oxide superconducting material.

When the superconducting properties of the oxide superconducting material produced in this way were measured, the electrical resistance became completely zero at 90%, confirming that it was an excellent oxide superconducting material.

Furthermore, cross-sectional observation of the obtained oxide superconducting material confirmed the presence of a dense reaction layer, and X-ray diffraction analysis revealed that orthorhombic crystals with a composition of Y IB atc u3o 7-8 were formed. I was able to confirm that.

"Effects of the Invention" - As explained above, the present invention impregnates a porous oxide layer having a composition of AtB ICu IOs formed on the outside of a base material with a molten B-Cu alloy, and then heat-treats the layer. As a result, a uniform diffusion reaction can occur throughout the porous oxide layer, and a homogeneous oxide superconducting layer can be generated throughout the oxide layer. Furthermore, compared to the case where an oxide superconductor is produced by sintering a mixed powder, element diffusion is made smoother and more uniformly, so that an oxide superconductor with homogeneous dense crystal grains can be produced. Therefore, by carrying out the method of the present invention, it is possible to produce an excellent oxide superconducting material having a high critical temperature and high critical current density.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a cross-sectional view of the base material, FIG. 2 is a cross-sectional view of the coating material, and FIG. 3 is a cross-sectional view of the coating material. -A cross-sectional view showing the state of the base material being immersed in the molten metal of Ba alloy, FIG. 4 is a cross-sectional view showing the base material after being immersed, and FIG. 5 is a cross-sectional view showing the oxide superconducting material. 1... Base material, 2... Oxide layer, 3... Covering material, 5... Bathtub, 6... Conveyance roller, 7... Composite material, 9... Oxide superconducting layer , A...Oxide superconducting material. Applicant: Fujikura Electric Cable Co., Ltd. Figure 1 口22to 1 Figure 3 Figure 5 Sono

Claims (1)

[Claims] General formula AB-Cu-O (where A is Sc, Y, L
B represents one or more elements of group IIIa of the periodic table such as a, Ho, and Er, and B represents one or more of elements of group IIa of the periodic table such as Sr and Ba. ), a porous oxide layer having a composition of A_2B_1Cu_1O_5 is formed on the outer periphery of a metal core material to form a coating material; This coating material is then immersed in a B-Cu alloy molten metal, and the pores of the oxide layer are filled with B.
- A method for manufacturing an oxide superconducting material, which comprises impregnating a molten Cu alloy to create a composite material, and then heat-treating the composite material in an oxygen-present atmosphere to generate an oxide superconductor.