JP2677001B2 - Siebrel phase compound superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a Chevrel phase compound superconductor.

[Prior Art] FIG. 4 is a cross-sectional view of a conventional PbMo ₆ S ₈ compound superconducting wire after cross-section reduction processing. In FIG. 4, (1) indicates Mo.
Material, Mo sulphide material, Pb material, Pb sulphide material, and sulfur material, a mixture material that is finally compounded in such a ratio that a PbMo ₆ S ₈ compound is produced. (2) is this mixture material A barrier material surrounding the outer periphery of (1), which is made of Nb, for example. (3) is a stabilizing material that surrounds the outer periphery of the barrier material (2), and is made of, for example, oxygen-free copper. (4) is a sheath material which surrounds the outer periphery of the stabilizing material (3) and is made of, for example, Cu-30% Ni. (5) is a complex formed by these.

A conventional method for manufacturing a PbMo ₆ S ₈ compound superconducting wire is a composite (5) in which a mixed material (1) is filled in a tube material of a barrier material (2), a stabilizing material (3) and a sheath material (4). After being subjected to cross-section reduction processing, it was heat-treated to internally generate a PbMo ₆ S ₈ based compound.

The role of the barrier material (2) is to prevent the sulfur component contained in the mixture material (1) from reacting with the stabilizing material (3) during the heat treatment, and has a high melting point such as Nb or Ta. Metals are mainly used. In addition, the role of the stabilizing material (3) is that when the superconductor changes to the normal conducting state for some reason,
It contributes to the stabilization of the superconductor as a thermal bypass path, and oxygen-free copper or the like is used.

The role of the sheath material (4) arises from the difference in the coefficient of thermal expansion between the chevrel phase compound and the barrier material (2) (chevrel phase compound: 9 to 10 × 10 ⁻⁶ , Nb: 7 × 10 ⁶ ). It is to reduce the residual strain of pulling during cooling. Cu-30% Ni, SU
S304 etc. are mainly used.

[Problems to be Solved by the Invention] In a conventional PbMo ₆ S ₈ compound superconducting wire, an oxygen-free copper tube as a stabilizing material is covered on the outside of a Nb tube as a barrier material, and a sheath material is further provided on the outside thereof. Since it is covered with a Cu-30% Ni tube, which has good electrical and thermal stability, the oxygen-free copper, which is a stabilizing material, has a small yield point and causes a yield. The compressive strain applied from the material to the barrier material (which has the effect of canceling or reducing the residual strain of pulling acting on the compound layer during cooling) cannot be effectively applied to the barrier material, and therefore the cotton There was a problem that the strain characteristics of the material were inferior. Furthermore, it is the fourth in the conventional wire rod.
As shown in the figure, since it has a four-layer structure, the ratio of the compound layer to the wire is small, and when magnetizing a long wire, the value of λJc, which is the effective critical current density of the wire, is small, making it compact. However, there was a problem that a Chevrel phase compound superconducting magnet with a high magnetic field could not be manufactured.

The present invention has been made to solve the above problems, and an object thereof is to obtain a Chevrel phase compound superconductor which is electrically and thermally stable and has excellent strain characteristics of a wire. Furthermore, the ratio of the compound layer to the wire is high and the value of λJc, which is the effective critical current density of the wire, is large, and as a result, it is possible to obtain a Chevrel phase compound superconducting magnet that is compact and generates a high magnetic field when magnetizing the wire. With the goal.

[Means for Solving the Problem] The Chevrel phase compound superconducting wire according to the present invention has a cross section of a composite composed of a mixture material, a barrier material, a stabilizing material, and a sheath material mixed in a ratio that produces a Chevrel phase compound. In the reduced and heat-treated Chevrel phase compound superconductor, both the stabilizing material and the sheath material are in contact with at least a part of the barrier material.

[Operation] The Chevrel phase compound superconducting wire according to the present invention is a composite material composed of a mixture material, a barrier material, a stabilizing material, and a sheath material mixed at a ratio that produces a Chevrel phase compound, and is subjected to cross-section reduction processing and heat treatment to obtain a Chevrel In the method for producing a phase compound superconductor, both the stabilizing material and the sheath material are in contact with the barrier material at least in part, so that they are electrically and thermally stable, and the sheath material from the outer peripheral layer is changed to the barrier material. Since the compressive strain can be directly applied to the compound layer, the residual strain of pulling acting on the compound layer during cooling can be offset or reduced, and a Chevrel phase compound superconductor having excellent strain characteristics can be obtained. Furthermore, since the ratio of the area of the compound layer to the cross section of the wire can be increased, the value of λJc, which is the effective critical current density of the wire, can be increased, and when the wire is magnetized, it is compact and the generated magnetic field is small. A high Chevrel phase compound superconducting magnet can be obtained.

[Examples] Hereinafter, a method for producing the Chevrel phase compound superconducting magnet of the present invention will be specifically described with reference to Examples.

Example 1 First, Mo, Pb, and M were used as constituent components of a PbMo ₆ S ₈ compound.
o ₂ S ₃ powder (particle size is 3μm, 44μm or less, 2μ
m, purity 99.9%) Pb: Mo ₂ S ₃ = 1.2: 0.8: 2.6
The mixed material was mixed as uniformly as possible in a molar ratio of, and molded by pressing to obtain a mixed material. This mixed material was inserted into a Nb tube as a barrier material, and put into a billet made of Cu-30% Ni, which is a sheath material, together with a square material of oxygen-free copper, which is a stabilizing material, to obtain a composite.
FIG. 1 is a cross-sectional view of this composite body. (1) is the mixed material obtained as described above, (2) is this mixed material (1)
Is a barrier material that surrounds the outer periphery of, for example, Nb. Reference numeral (3) is a stabilizing material, at least a portion of which is in contact with the outer periphery of the barrier material (2), and is made of, for example, oxygen-free copper. (4) is a sheath material, at least a portion of which is in contact with the outer periphery of the barrier material (2), and is made of, for example, Cu-30% Ni. (5) is a complex formed by these.

The billet of this composite (5) was vacuum-sealed with an electron beam welder, and then subjected to hydrostatic extrusion and cold drawing to reduce the cross-section, and wire-draw it to a diameter of 0.92 mm to a length of about 100 m. A PbMo ₆ S ₈ compound superconducting wire was obtained.

Next, this wire is wound on a ceramic bobbin with a diameter of 36 mm and a height of 50 mm for 12 turns in a solenoid shape, and both ends of this wire are end-sealed, then heat treated at a temperature of 1000 ° C for 2 hours in an argon atmosphere. Then, a PbMo ₆ S ₈ based compound was produced. A part of the wire rod obtained in this way is collected,
Both ends were soldered to a current lead, the required voltage tap was taken out, and the critical current (Ic) was measured in liquid helium under an external magnetic field of 15T.

As a result, Ic was 67.2A, critical current density (Jc) per compound layer, and Jc per total cross-sectional area were 328A / mm ² and
101.0A / mm ² next, Ic conventional wire, Jc per compound layer
And Jc per total cross-sectional area of 52.3A, 325A / mm ² and 7 respectively
Compared with 8.7 A / mm ² , Jc per compound layer is almost the same, but Jc per total cross-sectional area, that is, Ic of the wire is 28
It has been confirmed that the percentage has also improved. In addition, it was confirmed that the state of voltage generation in the vicinity of Ic of this wire rod was electrically and thermally stable without quenching as in the conventional wire rod.

Next, in order to investigate the strain-Ic characteristic of this wire, the strain dependence of Ic was measured in liquid helium under an external magnetic field of 9T. FIG. 2 is a distortion-Ic characteristic diagram, in which the vertical axis shows the value normalized by the maximum value of Ic, and the horizontal axis shows the distortion. In the figure, curves (A) and (B) show the characteristics of the wire rod according to the present invention and the conventional wire rod, respectively. As can be seen from FIG. 2, the characteristic of the wire rod according to the present invention is that the irreversible strain is 0.42%, and even if the strain exceeds 0.3%, the Ic is 90% or more as compared with the time when the strain is zero. The irreversible strain of the wire is 0.14%
Then, when the strain exceeds 0.2%, Ic becomes almost zero, and it is confirmed that the strain-Ic characteristic of the wire according to the present invention is significantly improved as compared with the characteristic of the conventional wire.

As a constituent of Example 2 PbMo ₆ S ₈ type _{compound, Mo, Pb, Mo 2 S} 3 powder (each particle size 3 [mu] m, 44 .mu.m or less, 2 [mu] m, even 99.9% both purity) of Pb: Mo: Mo ₂ S ₃ = 1.2: 0.8: 2.6 with a molar ratio of as uniform as possible, and pressed to obtain a mixed material. Insert this mixed material into the Nb pipe that is the barrier material,
I made a single core wire. Next, a billet (outer diameter 47 mm, made of Cu-30% Ni, having a cross-sectional shape as shown in FIG.
250mm in length, and the above single core wire
This was put together with a stabilizer and oxygen-free copper square pieces to form a composite. FIG. 3 is a cross-sectional view of this composite,
(1) is a mixed material, (2) is a barrier material, which is made of Nb, for example. (3) is a stabilizer, which is made of oxygen-free copper, for example.
(4) is a sheath material, which is made of Cu-30% Ni, for example.
(5) is a complex formed by these. After vacuum sealing the billet of this composite with an electron beam welder, the cross-section was reduced by hydrostatic extrusion and cold drawing, and the wire was drawn to a diameter of 0.92 mm and a length of approximately 400 m.
A PbMo ₆ S ₈ compound superconducting wire was obtained.

Next, this wire is wound on a ceramic bobbin with a diameter of 36 mm and a height of 50 mm for 12 turns in a solenoid shape, and both ends of this wire are end-sealed, then heat treated at a temperature of 1000 ° C for 2 hours in an argon atmosphere. Then, a PbMo ₆ S ₈ based compound was produced. A part of the wire rod obtained in this way is collected,
Both ends were soldered to a current lead, the required voltage tap was taken out, and the critical current (Ic) was measured in liquid helium under an external magnetic field of 15T.

As a result, Ic was 67.6 A, Jc per compound layer and Jc per total cross-sectional area were 321 A / mm ² and 101.8 A / mm ² , respectively,
Almost the same characteristics as the wire rod of Example 1 were obtained. Compared with the conventional wire rod, the Jc per compound layer was almost unchanged, but the Jc per total cross-sectional area, that is, the Ic of the wire rod was improved by 28% as in the wire rod of Example 1. It was confirmed.
In addition, it was confirmed that the state of voltage generation was electrically and thermally stable without quenching as in the case of conventional wire rods.

Next, in order to investigate the strain-Ic characteristic of this wire, the strain dependence of Ic was measured in liquid helium under an external magnetic field of 9T. As a result, the characteristics of the wire according to the present invention are irreversible strain of 0.
It was 40%, which was almost the same as that of the wire of Example 1, and it was confirmed that the irreversible strain of the conventional wire was significantly improved as compared with 0.14%.

As the Chevrel phase compound superconducting wire used in the present invention, a PbMo ₆ S ₈ based compound is typically studied for practical use because of its high characteristics, but the present invention is directed to the composition and constitution of the Chevrel phase compound wire. It goes without saying that it is effective in any case. That is, as a PbMo ₆ S ₈ type compound, for example, Pb _1.2 Mo ₆ S _7.8 , PbMo ₆ S ₇ , PbMo ₆ S ₇ , PbMo performed in the examples.
There are some compounds such as _5.1 S ₆ that have different values of Mo and S, but these are collectively described as PbMo ₆ S ₈ series compounds. Further, as M ′, for example, Ga, Bi, Sn, La, Ho, Eu, Gd, L
PbM ′ _x Mo ₆ S ₈ compounds with small additions of u, Y, Nd, In, etc.
Included in PbMo ₆ S ₈ series compounds. In addition to the Nb and Cu-30% Ni barrier materials and sheath materials constituting the wire, there are combinations such as Ta and SUS304 or Mo and SUS304, but the present invention is effective for any combination. Needless to say.

[Advantages of the Invention] As described above, the present invention is configured such that both the stabilizing material and the sheath material are in contact with at least a part of the barrier material, so that it is electrically and thermally stable, and the strain characteristic of the wire is excellent. It also has the effect of obtaining a Chevrel phase compound superconductor. Furthermore, since the ratio of the area of the compound layer to the cross section of the wire can be increased, the value of λJc, which is the effective critical current density of the wire, can be increased, and when the wire is magnetized, the generated magnetic field is compact. There is an effect that a high Chevrel phase compound superconducting magnet can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a Chevrel phase compound superconducting wire manufactured according to an embodiment of the present invention, FIG. 2 is a strain-Ic characteristic diagram of the wire manufactured according to the embodiment of the present invention, and FIG. A cross-sectional view of a wire produced according to another embodiment of the invention,
FIG. 4 is a cross-sectional view of a conventional Chevrel phase compound superconducting wire. In the figure, (1) is a mixed material, and (2) is a barrier material, which is made of Nb, for example. (3) is a stabilizer, which is made of oxygen-free copper, for example. (4) is a sheath material, which is made of Cu-30% Ni, for example. (5) is a complex formed by these. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A method for producing a Chevrel phase compound superconductor by subjecting a composite composed of a mixture material, a barrier material, a stabilizing compound material and a sheath material mixed in a proportion that produces a Chevrel phase compound, to cross-section reduction processing and heat treatment. In the Chebrel phase compound superconductor, the stabilizing material and the sheath material both contact at least a part of the barrier material.