JP2573967B2 - Manufacturing method of oxide superconducting material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxide superconducting material applicable to superconducting applied devices such as coils for superconducting magnets used in nuclear magnetic resonance devices and particle accelerators.

[Prior Art] Recently, various oxide superconductors have been discovered in which a critical temperature (Tc) at which a transition from a normal conducting state to a superconducting state is higher than the temperature of liquid nitrogen. This type of oxide superconductor has a general formula AB—Cu—O (where A is Y, Sc, La, Yb, Er,
One or more elements of group IIIa of the Periodic Table III such as Eu, Ho, and Dy;
B is an oxide represented by one or more elements of Group IIa of the Periodic Table II such as Be, Mg, Ca, Sr, and Ba), and is a conventional alloy which required cooling with liquid helium. Alternatively, since superconducting materials can be used under significantly more advantageous cooling conditions as compared with intermetallic compound superconductors, they have been studied as superconducting materials that are extremely promising in practical use.

Conventionally, as an example of a method of manufacturing a superconducting wire including such an oxide superconductor, a method described below with reference to FIG. 6 is known.

In order to manufacture an oxide superconducting wire, a mixed powder is prepared by mixing a plurality of raw material powders containing each element constituting an oxide superconductor represented by AB-Cu-O, and then the mixed powder is mixed. After removing unnecessary components by calcining, the calcined powder is heat-treated to be a superconducting powder, and then filled in 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 above-mentioned conventional method, it is difficult to completely and uniformly mix the raw material powders. There is a problem that does not become a structure, especially when a long superconducting wire is manufactured, a superconductor having a high critical current density cannot be obtained because a superconductor having a uniform crystal structure cannot be generated over the entire length of the wire. there were. Further, the superconducting wire A manufactured by the above-described method has a structure in which the brittle superconductor 2 is filled in the metal tube 1, so that the superconducting wire A is vulnerable to external force such as bending, and the superconductor 2 is cracked. There are drawbacks such as ease of use, and a problem of poor mechanical strength.

The present invention has been made in view of the above-described problems, and can generate a superconducting layer uniformly over the entire length. The superconducting layer has good adhesion to a substrate, high mechanical strength, and a thickness of the superconducting layer. Can be controlled to the desired value,
It is still another object of the present invention to provide a method for producing an oxide superconducting material having a superconducting layer of dense crystal grains.

"Means for Solving the Problem" The present invention provides a compound represented by the general formula A-
B-Cu-O (where A represents at least one kind of group IIIa element of the Periodic Table III such as Y, Sc, La, Yb, Er, Eu, Ho, Dy, and B represents the period of Ca, Sr, Ba, etc.) In the method for producing an oxide superconducting material having an oxide superconducting layer having the composition shown in Table II, the oxide superconducting layer has the composition shown in Table II. Forming a layer to form a coating material, forming copper oxide on at least a surface portion of the coating layer, and containing the A element, the B element, and Cu at a predetermined ratio outside the copper oxide layer. Forming an oxide layer to form a composite material,
400 lower than the heat treatment temperature to form oxide superconductors
An intermediate heat treatment at a temperature of ~ 600 ° C, followed by a final heat treatment at 850-1000 ° C to produce an oxide superconductor,
The oxide superconducting layer is formed by mutually diffusing the elements of each layer.

"Action" In order to interdiffuse Cu of the coating layer formed outside the base material, Cu and O of the copper oxide layer, and A and B elements of the mixed layer and Cu to form a superconducting layer, The superconducting layer is strongly bonded to the substrate by the diffusing element. In addition, since the heat treatment is performed on the composite material in which the element A, the element B, the Cu, and the O are uniformly present over the entire length, the element is uniformly diffused over the entire length and a uniform diffusion reaction occurs. Further, the thickness of the superconducting layer can be controlled by adjusting the thicknesses of the copper oxide layer, the mixed layer, and the additional layer.

Also, the intermediate heat treatment performed at a temperature lower than the formation temperature of the oxide superconductor causes the contained elements to interdiffuse across the coating layer, the copper oxide layer, and the mixture layer, thereby generating an intermediate layer. The diffusion reaction produces an oxide superconducting layer. By performing the intermediate heat treatment at a low temperature and then performing the heat treatment for generating an oxide superconductor at a high temperature, an oxide superconducting layer composed of dense crystal grains is generated.

"Example" FIGS. 1 to 5 show that the production method of the present invention is Y-Ba-
It is for describing an example applied to a method for producing a Cu-O-based oxide superconducting material.

In this embodiment, first, a tape shown in FIG. 1 made of a pure metal having a melting point of 800 ° C. or more, such as Ni, Zr, or Ti, or an alloy having a melting point of 800 ° C. or more, such as Ni—Cu, Ti—Al, or stainless steel. A long base material 10 having a shape is prepared.

Next, on the outer surface of the substrate 10, a plating method, a sputtering method, a vacuum evaporation method, or a method such as coating a foil body,
As shown in FIG. 2, a coating material 12 is manufactured by forming a coating layer 11 made of Cu and having a thickness of about several tens of μm.

Subsequently, a copper oxide layer 12a shown in FIG. 3 is formed on the outer peripheral surface of the coating layer 11 by an oxidation process described below. The oxidation treatment performed here is an anodization treatment in which an aqueous bath of an aqueous solution of an alkali metal or alkaline earth metal hydroxide such as NaOH or KOH is used as a treatment bath, and further, anodization is performed using ethanol, methanol, formic acid, or the like. Alternatively, a chemical oxidation treatment in which the coating material 12 is immersed in an aqueous solution of hydrogen peroxide or an aqueous solution of nitric acid is preferable. The copper oxide layer 12a is made of Cu ₂ O, CuO, Cu ₂ O ₃ or the like.

Next, a mixed layer 13 shown in FIG. 4 is formed on the outer surface of the copper oxide layer 12a to obtain a composite material 14. This mixed layer 13 is made of Y-
It contains the respective elements constituting the Ba-Cu-O-based oxide superconductor at a predetermined ratio, and is formed, for example, by a method described below.

To form the mixed layer 13, Y ₂ O ₃ powder, BaO powder and C
The mixed powder obtained by mixing u ₂ O powder at a predetermined ratio is mixed with a vehicle such as an epoxy resin to form a paste. Then, the paste is applied to the outer surface of the coating material 12 by a screen printing method or an application method using a spray gun to form the mixed layer 13. Note that, among the powders to be mixed with the paste, any of a Cu powder and a CuO powder may be used instead of the Cu ₂ O powder, or a mixture of these powders may be used.

Next, an intermediate heat treatment for heating the composite material 14 to a temperature of 400 to 600 ° C. for several tens of hours in an inert gas atmosphere such as Ar gas or N ₂ gas is performed. Due to this intermediate heat treatment, the diffusion of elements proceeds inside the composite material 14, and an intermediate layer in which Y, Ba, Cu, and O are interdiffused over the coating layer 11, the copper oxide layer 12a, and the mixed layer 13 is generated. In addition, when generating this intermediate layer,
Copper oxide layer 1 made of CuO at the boundary between coating layer 11 and mixed layer 13
The presence of 2a facilitates the diffusion reaction of each element.

Subsequently, a final heat treatment of heating at 850 to 1000 ° C. for several hours to several tens of hours in an oxidizing atmosphere such as an oxygen gas stream of 1 atm is performed, and thereafter, the final heat treatment is gradually cooled to room temperature, for example, at a rate of 100 ° C./hour. Heat treatment is performed. By this final heat treatment, the elements of the intermediate layer further diffuse and react to form the oxide superconducting layer 17 shown in FIG. 5, and a superconducting material (superconducting tape) B can be obtained. At the time of this heat treatment, a Cu—Ni alloy layer 18 is generated at the boundary between the base material 10 and the coating layer 11.

In the superconducting material B manufactured as described above, the base material
Coating layer 11, copper oxide layer 12a, and mixed layer 13 formed outside of layer 10
Over time, the superconducting layer 17 is generated by the mutual diffusion reaction of Cu and O, Y and Ba, so that the superconducting layer 17 is strongly bonded to the other layers. For this reason, the superconducting layer 17
The superconducting material B has a high mechanical strength and is resistant to bending and the like.

Further, the thickness of the superconducting layer 17 formed by the heat treatment can be controlled by adjusting the thickness of the copper oxide layer 12a and the mixed layer 13, and the composition of the superconducting layer 17 is also changed to the composition of the mixed layer 13. Can be controlled accordingly. When the final heat treatment is performed after the formation of the intermediate layer by the intermediate heat treatment as described above, the superconducting layer 17 having fine crystal grains and a high critical current density can be generated. By the way,
When the superconducting layer 17 is formed by one heat treatment, 1000
It is necessary to heat to a temperature of ℃ or more for several tens of hours, but if heating to such a high temperature for a long time, the crystal grains of the generated superconducting layer become coarse, so You can't get it. At this point, if the superconducting layer is formed after the formation of the intermediate layer as described above, the superconductor of dense crystal grains grows based on the dense crystal grains generated at 400 to 600 ° C., and , Heat treatment temperature
The temperature is kept within the range of 850 to 1000 ° C., and coarsening of crystal grains can be suppressed, and the heat treatment time can be shortened, so that the superconducting layer 17 having dense crystal grains can be generated.

By the way, the superconducting material B can be used alone for superconducting magnet coils or for power transport. In addition, for example, a large number of superconducting conductors may be stacked and housed inside a sheath to form a large-capacity superconducting conductor. It can also be used as

In addition, in the said Example, although the manufacturing method of the Y-Ba-Cu-O type | system | group oxide superconducting material was demonstrated, this invention can be applied to manufacture of another AB-Cu-O type | system | group superconducting material. Of course. When a superconducting material other than the Y-Ba-Cu-O-based material is manufactured, a different kind of superconducting powder may be used for forming the mixed layer 13. That is, when preparing a raw material powder, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm ,
Using at least one compound powder such as Yb, Lu, etc.
As the compound powder of the group a element, one or more compound powders such as Be, Sr, Mg, Ba, and Ra may be used. In addition, in the above-described embodiment, the tape-shaped base material 10 was used.
May be tubular or linear.

"Production Example" A nickel tape having a thickness of 0.2 mm and a width of 2 mm was plated in a copper sulfate bath, and a copper plating layer having a thickness of 30 µm was formed to form a coating material. Next, the coating material was subjected to anodizing treatment in an aqueous NaOH solution to form a CuO film having a thickness of 1 to 2 μm. Further, on the outer surface of this CuO film, Y ₂ O ₃ powder, BaO powder and Cu
A mixed powder prepared by mixing ₂ O powder at a ratio of Y: Ba: Cu = 10: 10: 1 was mixed with an epoxy resin to obtain a paste. This paste is applied to the coating material to a thickness of about 30 μm
Was formed to obtain a composite material.

This composite material was heated at 500 ° C. for 50 hours in an Ar gas atmosphere to form an intermediate layer. Furthermore, after heating at 900 ° C. for 12 hours in an oxygen atmosphere at 1 atm, the mixture was cooled to room temperature at a rate of 100 ° C./hour to obtain an oxide superconducting material.

When the critical temperature (Tc) of this oxide superconducting material was measured by a four-terminal method, it was confirmed that the resistance became 0 at 95K. Further, when a cross section of this superconducting material was observed, an interdiffusion layer of Y-Ba-Cu having a thickness of about 20 μm was observed, and when diffracted by an X-ray defractometer, Y: B
The diffraction line of the compound of a: Cu = 1: 2: 3 could be observed.

[Effects of the Invention] As described above, the present invention provides a coating layer formed outside a substrate, Cu and O of a copper oxide layer, and element A and B of a mixed layer.
In order to generate an oxide superconducting layer by interdiffusing elements and Cu by heat treatment, the generated superconducting layer is strongly bonded to the base material. For this reason, there is an effect that a superconducting material having good mechanical strength, having good bonding between the base material and the superconducting layer and being resistant to bending and the like can be produced.

In addition, since the superconducting layer is generated by mutually diffusing the elements of the coating layer, the copper oxide layer, and the mixed layer, the thickness of the superconducting layer is controlled by adjusting the thickness of the coating layer, the copper oxide layer, and the mixed layer. And a superconducting layer corresponding to the composition of the element contained in the mixed layer can be produced. Furthermore, since the elements of the coating layer, the copper oxide layer, and the mixed layer are diffused, there is an effect that a uniform superconducting layer can be generated over the entire length of the base material.

In addition, since the intermediate layer is generated by interdiffusing the elements of the coating layer, the copper oxide layer, and the mixed layer by the intermediate heat treatment, and then the intermediate layer is turned into a superconducting layer by the final heat treatment, the fine crystal grains generated by the intermediate heat treatment are formed. Since a superconducting layer having fine crystal grains can be generated based on the intermediate layer, there is an effect that a superconducting material having a high critical current density can be obtained.

[Brief description of the drawings]

1 to 5 are for explaining one embodiment of the present invention. FIG. 1 is a sectional view of a base material, FIG. 2 is a sectional view of a covering material, and FIG. FIG. 4 is a cross-sectional view of a composite material, FIG. 5 is a cross-sectional view of a superconducting material, and FIG. 6 is a cross-sectional view of an oxide superconducting wire manufactured by a conventional method. is there. 10 ... base material, 11 ... coating layer, 12 ... coating material, 12a ... copper oxide layer, 13 ... mixed layer, 14 ... composite material, 17 ... superconducting layer, B ... superconducting material.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshimitsu Ikeno 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Nobuyuki 1-5-1, Kiba 1-5-1 Kiba, Koto-ku, Tokyo Fujikura (72) Inventor Kyoji Tachikawa 3-13-29 Seijo, Setagaya-ku, Tokyo (56) References JP-A-64-60918 (JP, A)

Claims (1)

(57) [Claims] A compound of the formula AB-Cu-O (where A is Y, Sc, L
a, Yb, Er, Eu, Ho, Dy, etc., Periodic Table III, which represents at least one kind of Group a element, and B, which represents Ca, Sr, Ba, etc., at least one kind of Group IIa element. In a method for producing an oxide superconducting material comprising an oxide superconducting layer having a composition represented by, a coating layer formed of Cu is formed outside a metal core material to form a coating material. Forming a copper oxide on at least the surface portion of the layer, forming an oxide layer containing the A element, the B element, and Cu at a predetermined ratio outside the copper oxide layer to form a composite material, This composite material is subjected to an intermediate heat treatment at a temperature of 400 to 600 ° C. lower than the heat treatment temperature for generating an oxide superconductor, and then to a final heat treatment for generating an oxide superconductor at 850 to 1000 ° C. A method for producing an oxide superconducting material, wherein an element is interdiffused to form an oxide superconducting layer.