JPH0815020B2 - Method for manufacturing 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. represent at least one group IIIa metal element of the periodic table, and B represents at least one group IIa group element such as Be, Mg, Ca, Sr, Ba, etc. ), It can be used under significantly more advantageous cooling conditions than conventional alloy-based or intermetallic compound-based superconductors that had to be cooled with liquid helium. Research is being conducted as a promising superconducting material.

By the way, conventionally, as an example of a method for producing a superconducting wire including such an oxide superconductor, a method described below based on FIG. 10 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 this 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 in a metal tube and further reduced in diameter to obtain a wire having a desired diameter. The wire is heat-treated. As shown in FIG. 10, it is a method for producing a superconducting wire A in which a superconductor 2 is formed inside a metal tube 1.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional method, since it is difficult to mix the raw material powders completely uniformly, the entire superconductor 2 has a completely uniform crystal even if heat treatment is performed. There is a problem that it does not form a structure, especially when manufacturing a long superconducting wire, it is not possible to obtain a superconducting wire with a high critical current density because a superconductor with a uniform crystal structure cannot be generated over the entire wire was there. Further, in the superconducting wire A manufactured by the above-mentioned method, since the brittle superconductor 2 is filled inside the metal tube 1, it is vulnerable to external force such as bending, and the superconductor 2 is cracked. There is a problem that it is easy and there is a problem that mechanical strength is poor.

The present invention has been made in view of the above problems, it is possible to uniformly generate a superconducting layer over the entire length, the adhesion of the superconducting layer to the substrate is good, and the mechanical strength is high. The purpose is to provide a method.

"Means for Solving Problems" In the first invention of the present invention, in order to solve the above problems,
A-B-Cu-O system (where A is Y, Sc, La, Yb, Er, Eu, Ho,
Dy, etc., shows one or more kinds of Group IIIa metal elements of the periodic table, and B is
In the method for producing an oxide-based superconducting wire comprising a superconductor of Al, which represents an alkaline earth metal element such as Be, Mg, Ca, Sr, Ba, etc., a linear, tubular, or tape-shaped metal base material is used. A coating layer of pure copper is formed on the surface, and then a mixed material layer containing the compound of the element A and the compound of the element B is formed on the surface of the coating layer to form a laminated material, and then the superconducting material is formed on the laminated material. The first heat treatment performed at a temperature lower than the heat treatment temperature for generating a superheat, the second heat treatment performed at an inert gas atmosphere such as Ar gas or a vacuum atmosphere at a temperature at which a superconductor is generated, and an oxygen present atmosphere and a superconductivity A final heat treatment is performed at a temperature for forming a body, and oxygen in the coating layer and the atmosphere in the atmosphere at the time of the final heat treatment and the elements of the mixed material layer are mutually diffused to generate an oxide superconductor.

Further, in the second invention of the present invention, a coating layer of pure copper is formed on the surface of the base material, then an oxidation treatment is performed to form a copper oxide film on the coating layer, and then on the surface of the copper oxide film. A mixed material layer containing the compound of the element A and the compound of the element B is formed into a laminated material, and then the first heat treatment performed on the laminated material at a temperature lower than the heat treatment temperature for generating a superconductor; and Ar gas. A second heat treatment, which is performed in an inert gas atmosphere or a vacuum atmosphere at a temperature that produces a superconductor, and a final heat treatment that is performed in an oxygen-existing atmosphere and at a temperature that produces a superconductor. The elements of the copper film and the mixed material layer are mutually diffused to generate an oxide-based superconductor.

"Function" The superconductor is formed by mutually diffusing the coating layer Cu formed on the outside of the base material, O in the atmospheric gas during the heat treatment or Cu and O of the copper oxide film, and the elements A and B of the mixed material layer. In order to generate, the superconductor layer made of a superconductor is strongly bonded to the base material by the interdiffusing elements. In addition, over the entire length, A element and B element and Cu or A element and B element and Cu and O
Since heat treatment is applied to the laminated material in which and are uniformly present, uniform element diffusion is performed over all, and a uniform diffusion reaction occurs. Further, the thickness of the superconductor layer can be controlled by adjusting the thickness of the coating layer and / or the copper oxide layer and the mixed material layer.

"Example" FIGS. 1 to 6 are for explaining an example in which the manufacturing method of the first invention of the present invention is applied to a manufacturing method of a Y-Ba-Cu-O-based superconducting wire.

In this example, first, a tape-shaped long base material 10 made of Ni shown in FIG. 1 is prepared. The material of the base material 10 is not limited to Ni, and a single metal or alloy having a melting point of 800 ° C. or higher can be used, but a metal material having good oxidation resistance, for example, noble metal, Ti, Ta. , Zr, Hf,
Simple metals such as V and Nb, Cu-Ni alloys, Cu-Al alloys,
Ni-Al based alloys, Ti-V based alloys, monel metal, stainless steel and the like are particularly preferably used.

Next, on the outer surface of the base material 10, a plating method using a copper sulfate bath, a method of using a thin film forming means such as a CVD method or a sputtering method, the base material 10 is sandwiched between two copper plates, or the base material 10 is used. Is inserted into a pure copper tube, and the pure copper is clad by a rolling process and the like, as shown in Fig. 2.
A coating layer 11 having a thickness of several tens of μm is formed. Although the coating layer 11 is usually formed on the entire surface of the base material 10,
When the superconductor layer is formed only on one surface of the base material 10, it may be formed only on one surface of the base material 10.

Next, a mixed material layer 12 made of a mixed material containing a compound powder of yttrium and a compound powder of barium is formed on the surface of the coating layer 11 to obtain a laminated material 13 shown in FIG.

To form the mixed material layer 12 on the surface of the coating layer 11, for example, a mixed powder obtained by mixing yttrium oxide and barium oxide so as to have a predetermined mixing ratio is made into a sol in ethanol to form a mixed material, and this mixed material is used. This can be easily performed by an operation of continuously passing the base material 10 through the inside and adhering this material to the coating layer 11 on the surface of the base material 10. As the compounds of yttrium and barium, in addition to the above oxides, carbonates, halides such as chlorides and fluorides, and the like can be preferably used. Further, the method for forming the mixed material layer 12 on the surface of the coating layer 11 is not limited to the above method, for example, a binder or a solvent is added to the above mixed powder to form a slurry, and the slurry material is a doctor blade. A doctor blade method for uniformly coating the surface of the base material 10 with an apparatus, a method for spray coating the above mixed material, a thermal spraying method, a thin film forming method such as a CVD method or a sputtering method may be used. The mixed material layer 12 is usually formed on the entire surface of the base material 10, but it is not limited to this and may be formed on only one surface of the base material 10.

Next, the first heat treatment of heating the laminated material 13 to a temperature of 400 to 600 ° C. for several tens of hours in an atmosphere of an inert gas such as Ar gas or a vacuum atmosphere is performed. By the first heat treatment, diffusion of elements is started inside the laminated material 13 as shown in FIG. 4, and an intermediate layer 14 in which Y, Ba and Cu are mutually diffused in the coating layer 11 and the mixed material layer 12 is formed. To generate.

Subsequently, the second heat treatment for heating the laminated material 13 that has undergone the first heat treatment to a temperature of 600 to 1000 ° C. for several hours to several tens of hours in the same inert gas atmosphere or vacuum atmosphere as the first heat treatment. I do. By this second heat treatment, diffusion of elements in the coating layer 11 and the mixed material layer 12 progresses, and the intermediate layer 14 is expanded as shown in FIG.

Next, a final heat treatment of heating the laminated material 13 that has undergone the second heat treatment to 700 to 1000 ° C. for several hours to several tens hours in an oxidizing atmosphere such as an oxygen stream of 1 atm is performed, and then to room temperature, For example, the final heat treatment is performed by gradually cooling at a rate of 100 ° C./hour. By this final heat treatment, O in the atmospheric gas
Penetrates into the intermediate layer 14 and reacts with the Cu, Y and Ba elements of the intermediate layer 14, and as a result, the superconductor layer 15 made of the Y-Ba-Cu-O superconductor shown in FIG. Generated and superconducting wire B
Can be obtained. In addition, the elements of the base material 10 and the coating layer 11 are diffused, and the coating layer 11 is formed by the Cu-Ni alloy layer 16 shown in FIG.
Becomes

In the superconducting wire B manufactured as described above, Cu of the coating layer 11 formed outside the base material 10 and the mixed material layer 12
Y and Ba are mutually diffused by the first heat treatment and the second heat treatment to form the intermediate layer 14, and by performing the final heat treatment, O in the atmosphere gas permeates into the intermediate layer 14 and each of the intermediate layers 14 Since the superconductor layer 15 made of the Y-Ba-Cu-O superconductor is generated by reacting with the element, the superconductor layer 15 is strongly bonded to the other layers. Therefore, the superconductor layer 15 has good adhesion to the base material 10, and the superconducting wire B is strong against bending and the like and has a high mechanical strength.

Further, the thickness of the superconductor layer 15 formed by heat treatment can be controlled by adjusting the thicknesses of the coating layer 11 and the mixed material layer 12, and the composition of the superconductor layer 15 is also the mixed material layer 12. It can be controlled according to the composition and the coating amount. When the final heat treatment is performed after the intermediate layer 14 is formed by the first heat treatment and the second heat treatment as described above, the superconductor layer 15 having fine crystal grains with high critical current density is formed.
Can be generated. By the way, when the superconductor layer 15 is generated by one heat treatment, it is necessary to heat it to a temperature of 1000 ° C. or higher for several tens of hours. However, if it is heated to such a high temperature for a long time, the generated superconductor is generated. Since the crystal grains of the layer 15 are coarsened, it becomes impossible to obtain the superconductor layer 15 having a dense crystal grain. In this respect, if the superconductor layer 15 is generated after the intermediate layer is generated as described above,
Based on the dense crystal grains generated at 400-600 ℃, the superconductor of the dense crystal grains grows, and the heat treatment temperature is 70
It is possible to suppress the coarsening of crystal grains by controlling the temperature in the range of 0 to 1000 ° C. and shorten the heat treatment time, so that it is possible to generate the superconductor layer 15 having dense crystal grains.

Next, the production method of the second invention of the present invention is applied to Y-Ba-Cu-O.
An example applied to a method of manufacturing a superconducting wire of the system will be described.

In this example, as in the previous example, a tape-shaped long base material 10 made of Ni shown in FIG.
A coating layer 11 made of Cu and having a thickness of several tens of μm is formed on the surface of the.

Next, a copper oxide film 17 made of CuO is formed on the outer peripheral surface of the coating layer 11 by the oxidation treatment described below. The oxidation treatment performed here is an electrolytic bath of an aqueous solution of a hydroxide of an alkali metal or an alkaline earth metal such as NaOH or KOH as a treatment bath, and further an anodization treatment of anodizing using ethanol, methanol or formic acid. Alternatively, the coating layer
A chemical conversion treatment in which the base material 10 on which 11 is formed is immersed in a hydrogen peroxide aqueous solution or a nitric acid aqueous solution is suitable.

Next, on the outer surface of the copper oxide film 17 formed as described above,
A mixed material layer 12 made of a mixed material containing a compound powder of yttrium and a compound powder of barium is formed to obtain a laminated material 18 shown in FIG. In order to form the mixed material layer 12 on the outer surface of the copper oxide film 17, a method of continuously passing the base material 10 into the mixed material in the form of a sol in the mixed powder in the same manner as in the above example, A spray coating method of a mixed material, a doctor blade method, a thermal spraying method, a thin film forming method such as a CVD or sputtering method, and the like are preferably used. The mixed material layer 12 is usually formed on the entire surface of the base material 10, but it is not limited to this and may be formed on only one surface of the base material 10.

Next, this laminated material 18 is subjected to the same heat treatment as in the previous example.
First, the laminated material 18 is heated to 400 to 600 ° C. in an atmosphere of an inert gas such as Ar gas or N ₂ gas or a vacuum atmosphere.
1st heat processing which heats to the temperature of several dozen hours is performed. This first
Due to the heat treatment, the diffusion of the elements is started inside the laminated material 18, and the intermediate layer in which Cu, O, Y, and Ba interdiffuse is formed over the coating layer 11, the copper oxide film 17, and the mixed material layer 12. In addition,
During the formation of this intermediate layer, since the copper oxide film 17 made of CuO is present between the coating layer 11 and the mixed material layer 12, the diffusion reaction of each element is smoothly performed.

Subsequently, the second heat treatment of heating the laminated material 18 that has undergone the first heat treatment to a temperature of 600 to 1000 ° C. for several hours to several tens of hours in the same inert gas atmosphere or vacuum atmosphere as the first heat treatment. I do. By the second heat treatment, diffusion of elements in the coating layer 11, the copper oxide coating film 17, and the mixed material layer 12 proceeds, the intermediate layer is expanded, and Cu, O, Y, and part of Ba in the intermediate layer react. Then, a superconductor is generated.

Next, a final heat treatment is performed by heating the laminated material 18 that has undergone the second heat treatment to a temperature of 700 to 1000 ° C. for several hours to several tens of hours in an oxidizing atmosphere such as an oxygen stream of 1 atm, and then to room temperature. For example, the final heat treatment is performed by gradually cooling at a rate of 100 ° C./hour. By this final heat treatment, Cu, O, Y and Ba elements in the intermediate layer and O infiltrated into the intermediate layer from the atmospheric gas react with each other, and as a result, a superconductor made of a Y-Ba-Cu-O superconductor. The layer 15 is formed, and as a result, a superconducting wire B similar to that shown in FIG. 6 can be obtained. It should be noted that the elements of the base material 10 and the coating layer 11 are diffused and the coating layer 11
Forms the Cu—Ni alloy layer 16 as in the previous example.

In the superconducting wire B manufactured as described above, the superconducting layer 15 is strongly bonded to the other layers, so that the superconducting wire B has high mechanical strength and the thickness and composition of the superconducting layer 15 are high. Can be easily adjusted, since the final heat treatment is performed after the intermediate layer is produced, it is possible to produce the superconductor layer 15 having a high critical temperature of fine crystal grains, and the like, it is possible to obtain the same effect as the previous example. it can.

The superconducting wire B manufactured according to each of the above examples can be applied to a superconducting device such as a superconducting magnet coil or a superconducting wire for electric power transportation as it is, but in addition to that, for example, as shown in FIG. As described above, a large number of layers can be stacked and inserted into the metal sheath 19 to be used as a large capacity superconducting wire 20.

Further, in each of the above examples, the shape of the superconducting wire B is a tape, but the method of the present invention is not limited to this and may be applied to a linear or tubular superconducting wire. For example, on a base material 10a having a circular cross section, a coating layer 11 and a mixed material layer 12 of pure copper or a coating layer 11 and a copper oxide film 17 and a mixed material layer as in the above example.
By forming 12 in order and performing each heat treatment, a superconducting wire C having a circular cross section as shown in FIG. 9 can be manufactured.

[Production Example 1] On a pure Ni tape having a thickness of 0.2 mm and a width of 2 mm, a coating layer of pure copper having a thickness of about 30 µm was formed using a copper sulfate bath.

On the other hand, Y ₂ O ₃ and BaO powders were mixed with Y: Ba = 1: 2 (molar ratio).
The mixed powder mixed so as to have a ratio of was suspended in ethanol to prepare a mixed material for spraying. This mixed material was spray coated on the entire surface of the above-mentioned base material and then dried to form a mixed material layer having a thickness of about 30 μm on the coating layer to obtain a laminated material.

Next, this laminated material is placed in an Ar gas atmosphere at 500 ° C.
The first heat treatment of heating for 40 hours was performed. By this first heat treatment, Cu, O, and Y were formed in the coating layer and the mixed material layer.
It was confirmed that Ba was interdiffused to form an intermediate layer having a thickness of about 5 μm.

Subsequently, a second heat treatment of heating the laminated material at 900 ° C. for 12 hours in the same Ar gas atmosphere as the first heat treatment was performed. By this second heat treatment, the intermediate layer was expanded to about 40 to 50 μm.

Next, this is placed in an oxygen atmosphere of 1 atm at 850 ° C. for 24 hours.
After a final heat treatment for an hour, this was gradually cooled to room temperature at −100 ° C./hr. By the above operation, a superconducting wire having a superconductor layer made of a Y-Ba-Cu-O superconductor formed on one surface of a tape-shaped Ni substrate was manufactured.

The critical temperature (Tc) of the superconducting wire obtained in this way
As a result, Tc = 95K and excellent superconducting properties were exhibited. Also, when observing the cross section of this superconducting wire,
A superconductor layer having a thickness of about 45 μm in which Ba and Cu elements were mutually diffused was observed, and a diffraction line of YBa ₂ Cu ₃ O _7- x was confirmed by X-ray diffraction.

[Production Example 2] The Ni tape base material used in the previous example was used, and a coating layer made of Cu was formed on the surface of the base material as in the previous example. Next, this base material is anodized in a 20% NaOH aqueous solution to a thickness of 2
A μm copper oxide film (CuO) was formed. Next, this copper oxide film is spray coated with the mixed material as in the previous example,
A mixed material layer having a thickness of about 30 μm was formed to obtain a laminated material.

Next, in this laminated material, as in the previous example, in an Ar gas atmosphere, 50
First heat treatment of heating at 0 ℃ for 40 hours and 900 in Ar gas atmosphere
Second heat treatment of heating at ℃ for 12 hours, and at 850 ℃ for 24 hours in oxygen
A final heat treatment of heating for a time was performed.

By the above operation, Y-Ba is formed on one surface of the tape-shaped Ni base material.
A superconducting wire having a superconductor layer made of a —Cu—O superconductor was manufactured.

The critical temperature (Tc) of the superconducting wire obtained in this way
As a result of the measurement, Tc = 95K and excellent superconducting properties were shown as in the previous case. Observation of the cross section of this superconducting wire showed that each element of Y, Ba, and Cu diffused about 45 μm.
A superconducting layer with a thickness of m can be seen, and YBa ₂ Cu ₃ O _7- by X-ray diffraction.
The diffraction line of x was confirmed.

[Advantages of the Invention] As described above, the present invention provides a mixed material layer of Cu in the coating layer formed on the outside of the base material, O in the atmospheric gas during heat treatment or Cu and O in the copper oxide film. Since the element A and the element B are mutually diffused by heat treatment to generate an oxide-based superconductor layer, the generated superconductor layer is strongly bonded to the base material. Therefore, there is an effect that an oxide-based superconducting wire having good bonding between the base material and the superconducting layer and being strong against bending and having high mechanical strength can be manufactured.

Further, since the elements of the coating layer and the mixed material layer or the coating layer, the copper oxide film and the mixed material layer are mutually diffused to generate the superconductor layer, the coating layer and the mixed material layer or the coating layer and the copper oxide film are mixed. By adjusting the thickness of the material layer, the thickness of the superconductor layer can be controlled, and at the same time, the superconductor layer can be produced according to the composition of the elements contained in the mixed material layer. Furthermore, since the elements of the coating layer and the mixed material layer or the coating layer, the copper oxide film, and the mixed material layer are diffused, a uniform superconductor layer can be formed over all of the substrate, and when the copper oxide film is formed, In addition, the diffusion reaction of the elements can be smoothly carried out, and the production efficiency of the superconductor layer can be improved.

In addition, since the final heat treatment is performed after the intermediate layer is formed by the intermediate heat treatment, a superconductor layer of fine crystal grains can be generated based on the intermediate layer of fine crystal grains generated by the intermediate heat treatment. There is an effect that a high oxide-based superconducting wire can be obtained.

[Brief description of drawings]

1 to 6 are views for explaining an example of the first invention of the present invention. FIG. 1 is a perspective view of a base material, and FIG. 2 is a coating layer formed on the surface of the base material. Third perspective view showing the state
FIG. 4 is a cross-sectional view of the laminated material, FIG. 4 is a cross-sectional view of the laminated material subjected to the first heat treatment, FIG. 5 is a cross-sectional view of the laminated material subjected to the second heat treatment, and FIG. 6 is superconductivity. FIG. 7 is a cross-sectional view of the wire rod, FIG. 7 is a diagram for explaining the second invention of the present invention, and FIG. 8 is a cross-sectional view of the laminated wire rod. FIG. 8 is a diagram showing an application example of the superconducting wire rod according to the present invention. FIG. 9 is a perspective view of a superconducting wire, FIG. 9 is a view for explaining another example of the method of the present invention, a perspective view showing an example of a superconducting wire having a circular cross section, and FIG. 10 are manufactured by a conventional method. It is an oxide-based superconducting wire. 10 …… Base material 11 …… Overcoat layer 12 …… Mixed material layer 13, 18 …… Laminated material 14 …… Intermediate layer 15 …… Superconductor layer B, C …… Superconducting wire.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshimitsu Ikeno 1-5-1 Kiba, Koto-ku, Tokyo Within Fujikura Electric Wire Co., Ltd. (72) Nobuyuki Tekata, 1-1-5 Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Kyoji Tachikawa 3-13-29 Seijo, Setagaya-ku, Tokyo (56) References JP-A 64-60918 (JP, A) JP-A 63-281317 (JP, A) )

Claims (2)

[Claims] An AB--Cu--O system (where A is a periodic table II such as Y, Sc, La, Yb, Er, Eu, Ho, Dy, etc.)
In the method for producing an oxide-based superconducting wire, which comprises one or more of Group Ia metal elements, and B represents an alkaline earth metal element such as Be, Mg, Ca, Sr, and Ba), On the surface of a linear or tubular or tape-shaped metal substrate,
A coating layer of pure copper is formed, and then the above-mentioned A is formed on the surface of the coating layer.
A mixed material layer containing a compound of the element and the compound of the element B is formed into a laminated material, and then the laminated material is subjected to a first heat treatment at a temperature lower than a heat treatment temperature for generating a superconductor and Ar gas or the like. An oxide characterized by performing a second heat treatment in an inert gas atmosphere or a vacuum atmosphere at a temperature for producing a superconductor and a final heat treatment for performing a heat treatment in an oxygen existing atmosphere at a temperature at which a superconductor is produced. -Based superconducting wire manufacturing method. 2. A-B-Cu-O system (where A is Y, Sc, La, Yb, Er, Eu, Ho, Dy, etc.).
In the method for producing an oxide-based superconducting wire, which comprises one or more of Group Ia metal elements, and B represents an alkaline earth metal element such as Be, Mg, Ca, Sr, and Ba), On the surface of a linear or tubular or tape-shaped metal substrate,
A coating layer of pure copper is formed, then an oxidation treatment is performed to form a copper oxide film on the coating layer, and then a mixed material layer containing the compound of the A element and the compound of the B element is formed on the surface of the copper oxide film. A first heat treatment, which is performed at a temperature lower than the heat treatment temperature for forming a superconductor, and a temperature for forming a superconductor in an inert gas atmosphere such as Ar gas or in a vacuum atmosphere. 2. A method for producing an oxide-based superconducting wire, which comprises performing a second heat treatment in which the heat treatment is performed in step S4 and a final heat treatment in which the heat treatment is performed in an oxygen-present atmosphere at a temperature at which a superconductor is generated.