JP2901243B2 - Method for producing oxide-based superconducting wire - Google Patents

Description

The present invention relates to a superconducting magnet coil and a superconducting wire used for power transport and the like, and relates to a superconducting material using an oxide superconductor as a superconductor. "Prior art" Recently, various oxide-based superconductors have been discovered in which a critical temperature (Tc) at which a transition from a normal conducting state to a superconducting state exceeds a liquid nitrogen temperature. This type of oxide superconductor has a general formula AB-Cu-O (where A is Y, Sc, La,
Yb, Er, Eu, Ho, Dy, etc., represents at least one kind of group IIIa element of the Periodic Table III, such as Be, Mg, Ca, Sr, Ba.
Oxides), which can be used under significantly more advantageous cooling conditions than conventional alloy or intermetallic compound superconductors that required cooling with liquid helium. Research has been conducted as a very promising superconducting material for practical use. Conventionally, as an example of a method of manufacturing a superconducting wire including such an oxide-based superconductor, a method described below with reference to FIG. 6 is known. In order to produce an oxide-based superconducting wire, a plurality of raw material powders containing each element constituting the oxide-based superconductor represented by AB-Cu-O are mixed to prepare a mixed powder, and then the mixed powder is prepared. The powder is calcined to remove unnecessary components, and the calcined powder is heat-treated to form a superconducting powder, which is then filled into a metal tube, and further reduced in diameter to obtain a wire having a desired diameter. This is a method for manufacturing a superconducting wire A in which a superconductor 2 is formed inside a metal tube 1 as shown in FIG. [Problems to be Solved by the Invention] However, in the case of the superconducting wire A manufactured by the above-described conventional method, the superconducting powder is filled in a metal tube, and heat treatment is performed after diameter reduction processing to sinter the superconducting powder. Since the superconductor 2 is formed in this way, it is difficult to produce a dense superconductor 2, and there is a problem that a superconducting wire having a high critical current density cannot be obtained. Further, the above-described superconducting wire A has a disadvantage that it is weak to external force such as bending and easily cracks in the superconductor 2 because of the structure in which the brittle superconductor 2 is filled in the metal tube 1. There was a problem that the mechanical strength was inferior. The present invention has been made in view of the above problems, and by generating a dense superconductor on the surface of a base material, superconductivity characteristics such as critical current density are affected, and the adhesion of the superconducting layer to the base material is improved. It is an object of the present invention to provide a method for producing an oxide superconducting wire having good mechanical strength and high mechanical strength. "Means for Solving the Problems" The present invention provides ABCD as means for solving the above problems.
Corollary (where A is the periodic table of Y, Sc, La, Yb, Er, Eu, Ho, Dy, etc.)
III represents one or more elements of Group a elements, B represents one or more elements of Group IIa elements of the periodic table such as Be, Mg, Ca, Sr, Ba, etc., and C represents Cu, Ag, Au.
Periodic table Ib group element and Nb are Cu or two or more kinds containing Nb, and D is periodic table VIb element such as O, S, Se, etc. and periodic rule such as F, Cl, Br etc. Table VII 1 containing O among Group b elements
A superconducting wire comprising an oxide superconducting wire, comprising: a linear, tubular, or tape-shaped base material having a conductive property at least on a surface portion thereof; Electrodeposition is performed in an electrodeposition solution in which an oxide superconductor powder or an oxide superconductor precursor powder is dispersed, and an electrodeposition layer containing an element constituting the oxide superconductor is formed on the surface of the base material. Formed, then heat-treated, then subjected to a heat treatment of slow cooling, and promote the transformation of the crystal structure of the oxide superconductor from tetragonal to orthorhombic in the temperature range of 400 to 600 ° C during the slow cooling process The treatment is carried out for holding for a possible time, and then a coating layer is formed on the surface of the formed superconductor layer. [Function] An electrodeposition layer containing an element constituting the oxide superconductor is formed by electrodepositing the oxide superconductor powder or the oxide superconductor powder on the surface of the base material by electrophoretic electrodeposition. Thereafter, a heat treatment is performed to form a coating layer on the surface of the formed superconductor layer, whereby a dense superconductor layer is formed on the surface of the base material in a uniform state over the entire line. "Example" FIGS. 1 to 4 show that the production method of the present invention is Y-Ba-
This is for describing an example applied to a method for producing a Cu-O-based superconducting wire. The substrate 10 suitably used in the method of the present invention has a melting point
Precious metals, Ti, Ta, Z with excellent oxidation resistance at 800 ° C or higher
Simple metals such as r, Hf, V, Nb, Cu-Ni alloys, Cu-Al
Alloy, Ni-Al alloy, Ti-V alloy, Monel metal,
A metal wire such as stainless steel, a composite wire in which a surface of a ceramic fiber such as quartz glass or sapphire is coated with a metal such as Ag, or a carbon fiber is preferably used. In the example described here, as shown in FIG. 1, an example in which a superconducting wire is manufactured using a round base material 10 is shown. In this example, first, an electro-deposited layer containing all the elements constituting the Y-Ba-Cu-O-based superconductor is formed on the surface of the base material 10 by electrophoretic electrodeposition to form a superconducting element wire. . FIG. 2 is a view showing an example of an electrophoresis apparatus suitable for forming an electrodeposition layer on the surface of the base material 10, wherein reference numeral 21 denotes an electrodeposition tank;
Is an electrodeposition liquid. The electrodeposition liquid 22 is obtained by dispersing a Y-Ba-Cu-O-based superconducting powder in an organic solvent (dispersion medium) such as acetone. As the dispersion medium, in addition to acetone, an organic solvent other than acetone, such as xylene, a mixed solution of acetone and ethanol, and a mixed solution of acetone and xylene can be used. The concentration of the superconducting powder in the dispersion medium is 100 ml of the dispersion medium.
Is desirably in the range of 0.1 g to 20 g. When the concentration of the superconducting powder is set to 20 g or more per 100 ml of the dispersion medium, the superconducting powder is not electrodeposited in a dense and uniform state on the surface of the base material, and the concentration of the superconducting powder is 0.1 to 100 ml of the dispersion medium.
If it is less than g, the electrodeposition efficiency will be poor. This electrodeposition liquid 2
In 2, titanium oxide or the like serving as a sintering aid when the electrodeposition layer is sintered may be dispersed together with the superconductor powder. The superconducting powder has a particle size of 0.1 to 50 μm, and a fine powder having a particle size of 0.1 to 5 μm is particularly preferably used. As a method of producing this superconducting powder, for example,
Each raw material powder of Y ₂ O ₃ , BaCO ₃ , and CuO was mixed with Y: Ba: Cu = 1: 2: 3
(Molar ratio) to obtain a mixed powder by mixing uniformly,
Then, the mixed powder is placed in an oxygen atmosphere at 500 to 1000 ° C. for 1 hour.
A calcined powder is obtained by calcining for several tens of hours, and then a series of operations of compacting, heating, and pulverizing is performed once or twice or more on the calcined powder to obtain a Y-Ba-Cu-O system. A powder mixing method for producing superconducting powder is preferred. The heating performed after molding the calcined powder is desirably performed in an oxygen atmosphere at 800 to 1000 ° C. for 1 to several tens of hours. The method for producing the superconducting powder is not limited to the powder mixing method described above, but may be a coprecipitation method or a sol-gel method. Further, instead of the superconducting powder in the electrodeposition liquid 22, the calcined powder described above may be used. In order to form an electrodeposition layer on the surface of the substrate 10 by the electrophoresis apparatus shown in FIG. 2, the substrate 10 is placed in the electrodeposition liquid 22 contained in the electrodeposition bath 21 as shown by an arrow in the figure. While moving at a constant speed, the cathode of the substrate 10 was used.
A DC voltage is applied to the anode 23 disposed therein. In this electrodeposition operation, both the constant voltage method and the constant current density method are possible.If the constant voltage method is used, a voltage of 20 V or more may be applied. It is desirable that the density be in the range of 0.05 to 5 mA / cm ² . As the anode 23, a normal electrode material such as a stainless steel plate, a lead plate, and a carbon electrode can be used. As described above, by applying a DC voltage between the base material 10 serving as the cathode and the anode 23, the superconducting powder dispersed in the electrodeposition liquid 22 is positively charged, and the surface of the base material 10 serving as the cathode is Is electrodeposited. Then, a dense electrodeposition layer 11 made of a superconducting powder is formed on the surface of the base material 10 to form a superconducting element wire 12 shown in FIG. The superconducting wire 12 on which the electrodeposition layer 11 having a predetermined thickness is formed in the electrodeposition tank 21 is drawn out from the electrodeposition tank 21 as shown by an arrow in FIG. 2, and then dried by hot air. Then, an organic solvent such as acetone remaining on the surface portion is removed. Next, the superconducting wire 12 is subjected to a final heat treatment. This final heat treatment is performed by placing the superconducting wire 12 in an oxygen atmosphere at 800 to 1000
After heating at 1 ° C. for 1 minute to several tens of hours, the mixture is gradually cooled to room temperature. In this case, 400
Performing a process of holding for a predetermined time in a temperature range of ~ 600 ° C,
It promotes the transformation of the crystal structure of the oxide superconductor from tetragonal to orthorhombic. During this heat treatment, a heating means capable of continuously heating and gradually cooling the superconducting wire 12 moving at a predetermined speed, for example, a substrate moving at a predetermined speed using a long tunnel-type heating furnace or the like, is used. In step 10, each process of electrophoretic electrodeposition → drying → heat treatment may be performed continuously. The electrodeposition layer formed on the surface of the substrate 11 by this heat treatment
11 is sintered, and a uniform composition of Y-Ba-Cu-O
A superconductor layer 13 made of a system superconductor is formed. Through the above operations, a superconducting wire B having the superconducting layer 13 formed on the surface of the base material 10 as shown in FIG. 4 is obtained. Then, a coating layer 14 is formed on the surface of the superconducting wire B thus obtained. As a material of the coating layer 14, a metal such as Ag, Cu, Al, Ni, or Cu-Ni, or a synthetic resin such as an epoxy resin is preferably used. In the superconducting wire C shown in FIG. 5 in which the coating layer 14 is formed on the surface of the superconducting layer 13, the superconducting layer 13 is protected by the coating layer 14, and the deterioration of superconducting characteristics can be prevented for a long time. It prevents peeling of the superconductor layer 13 and generation of cracks, is resistant to bending and the like, and has excellent workability. In the above-described method for producing the superconducting wire B, the dense electrodeposition layer containing all the elements constituting the oxide superconductor by electrodepositing the oxide superconductor powder on the surface of the base material 10 by electrophoretic electrodeposition. Is formed and then subjected to a heat treatment, whereby the base material 10 is formed.
A dense superconductor layer 13 composed of a Y-Ba-Cu-O superconductor can be formed on the surface of the superconductor layer in a uniform state over the entire line, so that defects such as cracks may occur in the superconductor layer 13. Thus, a high-performance superconducting wire B having a high critical current density (Jc) can be manufactured. In the superconducting wire B, a dense electrodeposition layer 11 made of a Y-Ba-Cu-O-based superconducting powder is formed on the surface of the base material 10 by electrophoretic electrodeposition, followed by heat treatment. Since the body layer 13 is formed, the superconducting layer 13 has good adhesion to the base material 10, and the superconducting wire B has excellent flexibility and high mechanical strength. Further, on the surface of the base material 10, an electrodeposition layer 11 made of superconducting powder is formed by electrophoretic electrodeposition to form a superconducting wire 12, and then the superconducting wire 12 is subjected to a heat treatment to form a superconducting layer 13. Therefore, the thickness of superconductor layer 13 can be accurately controlled. Further, since the electrodeposition layer 11 is formed by electrophoretic electrodeposition, a relatively thick electrodeposition layer can be formed by a short-time electrodeposition operation, and the production efficiency of the superconducting wire B can be improved. Further, it is easy to continuously perform a series of operations of forming the electrodeposition layer 11 on the surface of the base material 10 and then performing a heat treatment, and can automate the production of the superconducting wire B, and The production efficiency of the superconducting wire B can be improved. In the above example, the round base material 10 was used as the base material, but the shape of the base material is not limited to this, and for example, various shapes of wire rods such as a square wire, a tape, and a tube are used. Can be used as a substrate. Further, in the above example, a Y-Ba-Cu-O-based superconductor was used as the superconductor, but the method of the present invention is not limited to this, and for example, Sc, La, Yb, Er, Use one or more elements of Group IIIa other than Y, such as Eu, Ho, Dy, etc.
Instead of a, one or more elements of Group IIa of the periodic table other than Ba, such as Be, Mg, Ca, and Sr, may be used. In the above example, the electrodeposition layer was formed on the surface of the base material 1 by one electrophoretic electrodeposition, but the electrophoretic electrodeposition may be performed two or more times. (Production Example 1) A nickel-made round wire having a diameter of 300 μm was used as a base material, and Y-Ba-Cu-O was formed on the surface of this base material using an electrophoretic electrodeposition apparatus having the same configuration as that shown in FIG. An electrodeposition layer made of a system superconducting powder was formed. This superconducting powder is composed of Y ₂ O ₃ , BaCO ₃ and C
uO is uniformly mixed so that Y: Ba: Cu = 1: 2: 3 (molar ratio), and this mixed powder is calcined at 800 ° C. for 24 hours in an acid-line atmosphere, and then compacted. Then, this compact was heated at 900 ° C. for 24 hours in an acid gas atmosphere, and further pulverized to obtain a superconducting powder having a particle size of about 0.1 to 1 μm. As the electrodeposition solution, a solution in which 5 g of the superconducting powder was dispersed in 100 ml of acetone was used. Electrophoretic electrodeposition conditions were set as follows. Applied voltage ‥‥ Constant voltage of DC 1.5KV Applied substrate moving speed ‥‥ 0.2 m / min Electrodeposition time 後 1 min After the superconducting wire after electrodeposition is dried with hot air to completely remove acetone , Introduced into the heating furnace, in pure oxygen,
After heating at 1000 ° C. for 1 hour, the mixture was gradually cooled to room temperature and wound up on a drum to obtain a long long conductive wire. As a result of measuring the critical temperature (Tc) and the critical current density (Jc) of the obtained superconducting wire, it showed excellent superconducting properties of Tc = 95K and Jc = 130A / cm ² . In addition, as a result of examining the cross section of the superconducting wire, it was confirmed that a dense superconductor layer of about 50 μm was formed on the surface of the base material, and the result of X-ray diffraction was Y ₁ Ba ₂ Cu ₃ O _7-X (rhombic ) Was confirmed. (Production Example 2) A round wire made of zirconium having a diameter of 250 μm was used as a base material, and the same electrodeposition operation as in Production Example 1 was performed on the surface of the base material to obtain a Y-Ba-Cu-O-based superconducting powder. Was formed. As the electrodeposition solution, a solution prepared by dispersing 5 g of the same superconducting powder as that used in Production Example 1 above and 0.1 g of titanium oxide (TiO ₂ ) as a sintering aid in 100 ml of acetone was used. used. The superconducting element wire after the electrodeposition operation is subjected to hot-air drying and heat treatment in the same manner as in Production Example 1, and the surface of the obtained wire material is coated with an epoxy resin by a dipping method to have a thickness of about 20 μm. Was formed to obtain a superconducting wire having the same configuration as that shown in FIG. As a result of measuring the critical temperature and the critical current density of the obtained superconducting wire, it showed excellent superconducting properties of Tc = 92K and Jc = 100A / cm ² . In addition, since the surface of the superconductor was covered with the epoxy resin, the superconducting wire had improved flexibility compared to the superconducting wire of Production Example 1 described above. Further, as a result of examining the cross section of this superconducting wire, a dense superconductor layer having a thickness of about 40 μm was confirmed on the surface of the base material. As a result of X-ray diffraction, Y ₁ Ba ₂ Cu ₃ O _7-X ( The presence of orthorhombic) was confirmed. [Effects of the Invention] As described above, in the method for producing an oxide superconducting wire according to the present invention, the powder of the oxide superconductor or the precursor powder of the oxide superconductor is applied to the surface of the base material by electrophoretic electrodeposition. To form a dense electrodeposition layer containing the elements constituting the oxide superconductor, and then, after heating, perform a heat treatment of gradually cooling,
In the course of this slow cooling treatment, a treatment is performed to maintain the crystal structure of the oxide superconductor in a temperature range of 400 to 600 ° C. for a time that can promote the transformation from the tetragonal system to the orthorhombic system. By forming a coating layer on the surface of the body layer, a dense oxide superconductor layer can be formed on the surface of the substrate in a uniform state over the entire line, and a high-performance superconducting wire can be manufactured. it can. Further, on the surface of the base material, an electrodeposition layer containing an element constituting the oxide superconductor is formed by electrophoretic electrodeposition, and then subjected to a heat treatment to form a superconductor layer. This makes it possible to produce an oxide superconducting wire having good adhesion, excellent flexibility, and high mechanical strength. Further, on the surface of the base material, an electrodeposition layer is formed by electrophoretic electrodeposition to form a superconducting element, and then the superconducting element is subjected to a heat treatment to generate a superconducting layer, so that the thickness of the superconducting layer is reduced. Can be precisely controlled. Further, since the electrodeposition layer is formed by electrophoretic electrodeposition, a relatively thick electrodeposition layer can be formed by a short-time electrodeposition operation, and the production efficiency of the superconducting wire can be improved. In addition, since a heat treatment is performed after the formation of the electrodeposition layer and a coating layer is formed on the surface of the formed superconductor layer, the superconductor layer is protected by this coating layer, and deterioration of the superconducting characteristics can be prevented for a long time. In addition to being able to prevent the superconductor layer from peeling or cracking, it is resistant to bending and the like and has excellent workability. In addition, in particular, by performing a process for maintaining the crystal structure of the oxide superconductor in a temperature range of 400 ° C. to 600 ° C. for a time capable of promoting transformation from tetragonal to orthorhombic during the slow cooling process, The crystal structure of the oxide superconductor constituting the superconductor layer can be transformed from tetragonal to orthorhombic, and a denser superconductor can be generated, and superconducting properties such as critical current density are more excellent. Superconducting wires can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 are views for explaining an example of the method of the present invention, wherein FIG. 1 is a sectional view of a base material, and FIG. FIG. 3 is a schematic configuration diagram showing an example of an electrophoretic electrodeposition apparatus suitable for forming an electrodeposition layer on the surface of a material, FIG. 3 is a cross-sectional view of a superconducting wire, FIG. 4 is a cross-sectional view of a superconducting wire, and FIG. Is a sectional view showing an application example of the superconducting wire shown in FIG. 4, and FIG.
The figure shows an oxide superconducting wire manufactured by a conventional method. 10 ... substrate, 11 ... electrodeposition layer, 13 ... superconductor layer, B, C ...
... Superconducting wires.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Koichi Saruwatari               Fujikura, 1-15-1 Kiba, Koto-ku, Tokyo               Inside Electric Wire Co., Ltd. (72) Inventor Satoshi Kono               Fujikura, 1-15-1 Kiba, Koto-ku, Tokyo               Inside Electric Wire Co., Ltd. (72) Inventor Yoshimitsu Ikeno               Fujikura, 1-15-1 Kiba, Koto-ku, Tokyo               Inside Electric Wire Co., Ltd. (72) Inventor Nobuyuki Sadakata               Fujikura, 1-15-1 Kiba, Koto-ku, Tokyo               Inside Electric Wire Co., Ltd. (72) Inventor Mikio Nakagawa               Fujikura, 1-15-1 Kiba, Koto-ku, Tokyo               Inside Electric Wire Co., Ltd. (72) Inventor Toshio Usui               Fujikura, 1-15-1 Kiba, Koto-ku, Tokyo               Inside Electric Wire Co., Ltd. (72) Inventor Yu Sugimoto               Fujikura, 1-15-1 Kiba, Koto-ku, Tokyo               Inside Electric Wire Co., Ltd.                (56) References JP-A-64-65299 (JP, A)                 JP-A-64-40305 (JP, A)                 JP-A-63-241818 (JP, A)                 JP-A-64-41122 (JP, A)                 JP-A-64-43921 (JP, A)

Claims (1)

(57) [Claims] ABCD system (where A is the periodic table II such as Y, Sc, La, Yb, Er, Eu, Ho, Dy, etc.)
I represents at least one kind of group A element, B represents one or more kinds of group A element such as Be, Mg, Ca, Sr, Ba, and C represents C. Periodic table such as Cu, Ag, Au etc. Cu or Cu containing Ib group element and Nb 2
And D represents at least one element of Group VIb of the Periodic Table such as O, S, Se and the like, and Group VIIb of the Periodic Table VII such as F, Cl and Br. A method for producing an oxide-based superconducting wire comprising a superconductor, comprising: a powder or oxide of the oxide superconductor, wherein a base material having a linear, tubular, or tape-like shape and having at least a surface portion having conductivity is used as a cathode; Performing electrophoretic electrodeposition in an electrodeposition solution in which a precursor powder of a superconductor is dispersed, forming an electrodeposition layer containing an element constituting the oxide superconductor on the surface of the base material, and after heating, A heat treatment for slow cooling is performed, and a process for maintaining the crystal structure of the oxide superconductor for a period of time capable of promoting transformation from tetragonal to orthorhombic in a temperature range of 400 to 600 ° C. is performed during the slow cooling. Forming a coating layer on the surface of the formed superconductor layer; Method of manufacturing the wire.