Copper oxide-based superconductor, superconductive wire member, and method for repairing copper oxide-based superconductor

Abstract

The present invention pertains to a copper oxide-based superconductor containing a REBCO-based superconductive material represented by general formula (1), and an oxygen storage material (in formula (1), RE1 is constituted of one or a plurality of elements selected from the group consisting of Sr, Ba, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and satisfies 0 ≤ x ≤ 1).

Description

Copper oxide superconductor, superconducting wire, and method for repairing copper oxide superconductor

[0001] The present invention relates to a copper oxide-based superconductor, a superconducting wire, and a method for repairing a copper oxide-based superconductor. This application claims priority based on Japanese Patent Application No. 2024-093062, filed on June 7, 2024, the contents of which are incorporated herein by reference.

[0002] Superconducting magnets using superconductors play an essential role in magnetic confinement nuclear fusion reactors. Furthermore, for the commercialization and miniaturization of nuclear fusion reactors, the copper oxide high-temperature superconductor REBa2Cu3O, which has superconducting properties far superior to those of conventional low-temperature superconductors, is required. 7-x (REBCO) is expected to be a promising candidate material for magnet applications.

[0003] Therefore, research into oxygen gas production technology using oxygen storage materials is underway (for example, Non-Patent Documents 1 and 2).

[0004] Thermodynamics of oxygen absorption / desorption reactions in oxygen storage materials BaLnMn2O5+δ (Ln = La, Nd, Gd, Y), Teruki Motohashi, Department of Materials and Life Chemistry, Faculty of Engineering, Kanagawa University Oxygen Nonstoichiometry in YBaCo4O7+δ: Large Low-Temperature Oxygen Absorption / Desorption Capability M. Karppinen, et al

[0005] However, when using superconducting magnets in a fusion reactor, if the superconductor is continuously irradiated with neutrons generated during the fusion reaction, the superconducting transition temperature Tc and critical current density Jc decrease, making it impossible to maintain the superconducting state. Damage from irradiation is also a serious problem for REBCO magnets. In particular, as fusion reactors become smaller, (a) the neutron flux increases due to the increased plasma density, and (b) the protective walls become thinner, making neutron shielding more difficult, making the problem of radiation damage even more serious.

[0006] The inventors have been developing HE-type REBCO (hereinafter referred to as HE-REBCO) by incorporating the concept of high-entropy alloys into REBCO. As a result of He ion irradiation experiments on the fabricated HE-REBCO thin film, it was found that the decrease in Tc after irradiation was significantly suppressed in HE-REBCO compared to conventional REBCO samples (Fig. 10). That is, the general formula is REBa2Cu3O 7-z In the REBCO superconductor represented by the formula (YBa2Cu3O), there is one rare earth element present at the RE site. 7-z ) compared to three types (Y 0.33 Gd 0.33 Dy 0.33 Ba2Cu3O 7-z ), four kinds (Y 0.25 Gd 0.25 Dy 0.25 Ho 0.25 Ba2Cu3O 7-z ) or five kinds (Y 0.20 Gd 0.20 Dy 0.20 Ho 0.20 Yb 0.20 Ba2Cu3O 7-z ) is the superconducting transition temperature T ｃ As shown in FIG. 10, in the superconductor having one rare earth element at the RE site, the superconducting transition temperature before ion irradiation was 86.0 K, and the superconducting transition temperature T ｃ is 73.0 K, and the superconducting transition temperature T ｃ In contrast, the decrease in the superconducting transition temperature T before and after irradiation of REBCO superconductors with three, four, and five rare earth elements present at the RE site was 13.0 K. ｃ The decreases in temperature were 0.5 K, 1.0 K, and 1.0 K, respectively. Furthermore, the superconducting transition temperatures after the irradiation tests were all 81.5 K or higher. However, there is still a need to improve the radiation resistance.

[0007] There are two main reasons why improved radiation resistance is required: 1. The need for smaller and thinner protective walls due to the miniaturization of reactors. 2. The increase in the amount of neutron irradiation per unit area.

[0008] The HE-REBCO invented in the previous research by the inventors has a superconducting transition temperature T c Although it has high radiation resistance with respect to the critical current density J c Regarding REBCO, the decrease after irradiation remains an issue. It is also known that irradiation also causes a decrease in the critical current density Jc in other REBCOs. The decrease in critical current density due to irradiation is thought to be caused by the release of oxygen atoms in the REBCO-based superconductor material to the outside, which causes oxygen vacancies in the REBCO-based superconductor. Therefore, there is a need to provide a means to suppress the decrease in critical current density after irradiation.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a copper oxide-based superconductor that can repair an oxygen-deficient REBCO-based superconductor and improve the critical current density, a superconducting wire including the copper oxide-based superconductor, and a method for repairing a copper oxide-based superconductor.

[0010] In order to solve the above problems, the present invention provides the following means.

[0011] [1] A copper oxide-based superconductor according to one embodiment of the present invention comprises a REBCO-based superconducting material represented by general formula (1) and an oxygen storage material, ２ Cu ３ O ７－ｘ ...(1) Copper oxide superconductor (In formula (1), RE is composed of one or more elements selected from the group consisting of Sr, Ba, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and satisfies 0≦x≦1.) In the copper oxide superconductor, the oxygen storage material is typically introduced into the REBCO-based superconducting material.

[0012] [2] A copper oxide-based superconductor according to one embodiment of the present invention comprises a REBCO-based superconducting material represented by general formula (1) and REBa ２ Cu３ O ７－ｘ ...(1) an oxygen storage material provided in contact with the REBCO-based superconducting material (in formula (1), RE is composed of one or more elements selected from the group consisting of Sr, Ba, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and satisfies 0≦x≦1). A typical example of a copper oxide-based superconductor includes a layer made of a REBCO-based superconducting material, and a layer made of an oxygen storage material provided in contact with the layer.

[0013] [3] In the copper oxide superconductor according to the above [1] or [2], the oxygen storage material is YBaCo ４ O ７＋δ and BaLnMn ２ O ５＋δ and Ca ２ AlMnO ５＋δ and (0≦δ≦1).

[0014] [4] In the copper oxide-based superconductors according to the above [1] to [3], the oxygen storage material is CeO ２ and CeO ２ -ZrO ２ and TiO ２ and ZrO ２ and SnO ２ And, Ta ２ O ５ and MnO ２ And Co ３ O ４ and RuO ２ and IrO ２ and, it may be any one or more selected from the group consisting of:

[0015] [5] In the copper oxide-based superconductors according to the above [1] to [4], the oxygen storage material may be an iron-based oxide having a perovskite structure.

[0016] [6] In the copper oxide superconductors according to the above [1] to [5], the oxygen storage material is α-Fe ２ O ３ may be.

[0017] [7] In the copper oxide superconductors according to [1] to [6] above, the REBCO-based superconducting material is represented by general formula (1), where RE may be composed of one or more elements selected from the group consisting of Y, Gd, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu, or may be composed of three or more elements selected from the group.) As a high-entropy REBCO-based superconducting material having three or more rare earth elements at the RE site, for example, one described in PCT / JP2024 / 018667 can be used.

[0018] [8] In the copper oxide superconductors according to the above [1] to [7], in the above formula (1), RE may be composed of four or more kinds of rare earth elements.

[0019] [9] The copper oxide superconductors of [1] to [8] above may be such that, in the formula (1), RE is composed of Y, Gd, and X, and X is composed of one or more elements selected from the group consisting of Sr, Ba, Ca, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0020]

[10] The copper oxide superconductors according to the above [1] to [9] may be such that, in the above formula (1), RE may be represented by the general formula (2): Y ａ Gd ｂ X ｃ ... (2) (0.05≦a≦0.9, 0.05≦b≦0.9, 0.05≦c≦0.9).

[0021]

[11] In the copper oxide superconductors according to the above [1] to

[10] , in the above formula (2), RE is composed of five or more kinds of rare earth elements, and the mixing entropy ΔS of the RE site is ｍｉｘ may be 1.4R or more.

[0022]

[12] In the copper oxide-based superconductor according to the above [1] or [2], the content of the oxygen storage material is more than 0 wt % and not more than 90 wt %, where the content is in weight percent.

[0023]

[13] In the copper oxide-based superconductors according to any one of [1] to

[12] above, the oxygen storage material may have a temperature range for storing oxygen of 200°C or higher and 350°C or lower, and a temperature range for releasing the stored oxygen of more than 350°C and 500°C or lower.

[0024]

[14] A superconducting wire according to one embodiment of the present invention comprises a superconducting laminate having a base layer and a superconducting layer formed on the base layer and containing a copper oxide-based superconductor according to any one of [1] to

[13] above, a stabilizing layer surrounding the outer periphery of the superconducting laminate, and a conducting layer located between the superconducting laminate and the stabilizing layer and in contact with the superconducting layer.

[0025]

[15] A method for repairing a copper oxide superconductor according to one embodiment of the present invention includes a heating step of heating the copper oxide superconductor according to any one of the above [1] to

[14] to induce oxygen diffusion from the oxygen storage material to a REBCO-based superconductor, thereby repairing oxygen vacancies in the REBCO-based superconductor.

[0026]

[16] In the method for repairing a copper oxide superconductor according to

[15] above, in the heating step, the copper oxide superconductor may be heated at a temperature of 150° C. or higher and 500° C. or lower. The temperature to which the copper oxide superconductor is heated may be 200° C. or higher and 300° C. or higher and 450° C. or lower, or may be a temperature higher than 350° C. and 450° C. or lower.

[0027]

[17] In the method for repairing a copper oxide-based superconductor according to any one of

[14] to

[16] above, a superconducting wire is used, the wire comprising a copper oxide-based superconductor, a stabilizing layer surrounding the outer periphery of the wire, and a conducting layer located between the wire and the stabilizing layer and in contact with the copper oxide-based superconductor, wherein the conducting layer may be heated by applying an electric current in the heating step.

[18] In the method for repairing a copper oxide-based superconductor according to any one of

[14] to

[17] above, the heating step may include a first step of heating the copper oxide-based superconductor at a first temperature of 150°C or higher, and a second step of heating at a second temperature higher than the first temperature and not higher than 500°C.

[0028] According to the present invention, it is possible to provide a means for repairing an oxygen-deficient REBCO-based superconductor and improving the critical current density after irradiation.

[0029] [Correction based on Rule 91 17.06.2025] A partially sectional perspective view showing an example of the configuration of a superconducting wire according to one embodiment of the present invention. A diagram for explaining the configuration of a superconducting laminate provided in the superconducting wire of FIG. 1. A diagram showing the configuration of a superconducting laminate according to a modified example of FIG. 2. A diagram showing the configuration of a superconducting wire according to a modified example of FIG. 1. A diagram for explaining a manufacturing method of a superconductor according to one embodiment of the present invention, showing a deposition process performed by a PLD method. An X-ray diffraction image of a superconducting layer in the structure of Example 1. FIG. 7(a) is a graph showing the temperature dependence of magnetization of the structure of Example 1 before an ion irradiation test, and FIG. 7(b) is an enlarged view of a partial area of ​​FIG. 7(a). A graph showing the magnetic field dependence of the critical current density of the structure of Example 1 at each temperature. A graph showing the temperature dependence of magnetization after an ion irradiation test of the structure of Example 1. A graph showing the results of an irradiation experiment on REBCO and HE-type REBCO, showing the critical current density before and after irradiation with 1 MeV He ions (energy equivalent to that of a neutron beam).

[0030] An example of an embodiment of the present invention will be described in detail below with reference to the drawings. The drawings used in the following description may conveniently show enlarged characteristic portions to make the features of the present invention easier to understand, or may show an example of an embodiment. Therefore, the dimensional ratios of each component may differ from the actual ones, or only specific means may be described. The present invention is not limited to these examples, and can be implemented by appropriately modifying and combining the design within the scope of its gist.

[0031] [Superconducting wire] Fig. 1 is a partial cross-sectional perspective view of a superconducting wire according to one embodiment of the present invention. Fig. 2 is a diagram for explaining the configuration of a superconducting laminate provided in the superconducting wire of Fig. 1. For convenience, Fig. 2 shows the ends of each layer shifted.

[0032] The superconducting wire 10 shown in FIG. 1 includes a superconducting laminate 5, a stabilizing layer 6, and a conductive layer 4 provided between the superconducting laminate 5 and the stabilizing layer 6. The stabilizing layer 6 extends along the superconducting laminate 5 and is provided so as to contact its main surface and side surfaces. The stabilizing layer 6 is formed so as to surround the superconducting laminate 5. The stabilizing layer 6 includes, for example, a first stabilizing layer 6a provided in a position close to the superconducting laminate 5 and a second stabilizing layer 6b provided outside the first stabilizing layer 6a. The stabilizing layer 6 functions as a bypass section that commutates a current when a superconducting layer included in the superconducting laminate 5, described in detail below, transitions to a normal conducting state.

[0033] Examples of the stabilization layer 6 include metals such as copper, copper alloy, aluminum, aluminum alloy, and silver. Examples of copper alloys that can be used as the stabilization layer 6 include Cu-Zn alloys and Cu-Ni alloys. The thickness of the stabilization layer 6 is, for example, several μm to 300 μm. The stabilization layer 6 can be formed by plating (e.g., electrolytic plating). The stabilization layer 6 may be a single layer or a multi-layer layer as shown in FIG. 1 . For example, the multi-layer stabilization layer 6 may have a first stabilization layer 6a made of silver, copper, or the like, and a second stabilization layer 6b made of copper, aluminum, or the like. However, the present invention is not limited to this example, and any of the above materials can be selected and used.

[0034] The conductive layer 4 is resistance heated to heat the superconducting layer 3. That is, the copper oxide-based superconductor containing the REBCO-based superconducting material 31 and the oxygen storage material 32, which will be described in detail later, is heated, oxygen diffusion from the oxygen storage material 32 to the REBCO-based superconducting material 31 is induced, and oxygen vacancies in the REBCO-based superconducting material 31 are repaired.

[0035] <Laminate> The superconducting laminate 5 shown in Fig. 2 includes a substrate 1, an intermediate layer 2, and a superconducting layer 3. Fig. 2 shows an example in which the intermediate layer 2 and the superconducting layer 3 are formed on one main surface of the substrate 1, but this embodiment is not limited to this example, and may have a configuration in which the intermediate layer 2 and the superconducting layer 3 are formed on both main surfaces of the substrate 1. In this embodiment, the substrate 1, the intermediate layer 2, and the superconducting layer 3 may be collectively referred to as a wire rod in some cases.

[0036] (Substrate) The substrate 1 is made of, for example, a metal. The substrate 1 is made of, for example, a nickel alloy, stainless steel, an oriented Ni-W alloy in which a texture is introduced into nickel steel, Hastelloy (registered trademark), etc. The thickness of the substrate 1 is, for example, 10 to 500 μm.

[0037] An intermediate layer 2 is preferably provided on the main surface S1 of the substrate 1, but the intermediate layer 2 can be omitted. In a superconducting laminate 5 in which the substrate 1, the intermediate layer 2, and the superconducting layer 3 are formed in this order as shown in Figure 2, the substrate 1 and the intermediate layer 2 are collectively referred to as an underlayer 12.

[0038] (Intermediate Layer) The intermediate layer 2 is provided between the substrate 1 and the superconducting layer 3. The intermediate layer 2 is composed of, for example, multiple layers. FIG. 3 shows an example in which the intermediate layer 2 includes, in order from the side closest to the substrate 1, a first intermediate layer 2a, a second intermediate layer 2b, and a third intermediate layer 2c. The intermediate layer 2 has, for example, multiple layers, such as a bed layer, an orientation layer, and a cap layer, each of which has a different function. For example, the surface of the intermediate layer 2 facing the superconducting layer 3 and its vicinity are composed of a single crystal. The intermediate layer 2 may have a configuration other than three layers, such as a single layer. When the intermediate layer 2 is a single layer, any of the materials exemplified below as the first intermediate layer 2a, the second intermediate layer 2b, and the third intermediate layer 2c may be used, and it is preferable that the surface is single crystal.

[0039] The first intermediate layer 2a is, for example, a bed layer. The bed layer serves to reduce the reaction at the interface between the substrate 1 and the superconducting layer 3 and to improve the orientation of the layer formed thereon. Examples of the material for the bed layer include CeO ２ , Er ２ O ３ , Y ２ O ３ , Dy ２ O ３ , Eu ２ O ３ , Ho ２ O ３ , La ２ O ３ etc.

[0040] The second intermediate layer 2b is, for example, an orientation layer. When a cap layer is formed thereon, the orientation layer is provided to control the crystal orientation of the cap layer. The orientation layer may be, for example, Gd ２ Zr ２ O ７ , MgO, ZrO ２ -Y ２ O ３ (YSZ), SrTiO ３ , CeO ２ , Y ２ O ３ , Al ２ O ３ , Gd ２ O ３ , Zr ２ O ３ , Ho ２ O ３ , Nd ２ O ３ The alignment layer is preferably formed by an IBAD (Ion Beam Assisted Deposition) method.

[0041] The third intermediate layer 2c is, for example, a cap layer. The cap layer is formed on the surface of the orientation layer and is made of a material whose crystal grains can self-orient in the in-plane direction. For example, the cap layer may be made of CeO ２ , Y ２ O ３ , Al ２ O ３ , Gd ２ O ３ , ZrO ２ , Y.S.Z., Ho ２ O ３ , Nd ２ O ３ , LaMnO ３ It is formed by the following:

[0042] (Superconducting Layer) The superconducting layer 3 is formed on, for example, the underlayer 12. The superconducting layer 3 contains a REBCO-based superconducting material 31 represented by the general formula (1) and an oxygen storage material 32. ２ Cu ３ O ７－ｘ... (1) (In formula (1), RE is composed of one or more elements selected from the group consisting of Sr, Ba, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and satisfies 0≦x≦1.)

[0043] In this embodiment, the REBCO-based superconducting material 31 and the oxygen storage material 32 are referred to as a copper oxide-based superconductor. In the superconducting layer 3, the oxygen storage material 32 is provided, for example, scattered throughout the REBCO-based superconducting material 31. That is, the superconducting layer 3 has, for example, a sea-island structure in which the REBCO-based superconducting material forms a sea and the oxygen storage material 32 forms islands.

[0044] In the superconducting layer 3, the content of the oxygen storage material 32 is, for example, more than 0 wt % and not more than 90 wt %, preferably 10 wt % to 50 wt %, and more preferably 10 wt % to 30 wt %. Preferably, the oxygen storage material 32 is YBaCo ４ O ７＋δ In the case of less than 20 wt%, CeO ２ In this case, it is 20 wt % or less.

[0045] REBCO-based superconducting material 31 is a REBCO-based superconducting material represented by the above formula (1). From the viewpoint of improving the radiation resistance, the REBCO-based superconducting material 31 has a mixing entropy ΔS of the atomic site of RE, which is a rare earth element. ｍｉｘ may be 1.1R or more, 1.39R or more, or 1.5R or more. Here, R represents the gas constant. Mixing entropy ΔS ｍｉｘ REBCO superconductors with a mixing entropy ΔS of 1.1R or more are composed of three or more rare earth elements. ｍｉｘ A HE-REBCO superconductor having an RE2 of 1.39R or more is, for example, composed of four or more rare earth elements.

[0046] The rare earth element preferably includes Y and Gd, and more preferably includes at least one of Dy and Yb. The rare earth element RE may also be composed of Y, Gd, and X. X is, for example, composed of one or more elements selected from the group consisting of Sr, Ba, Ca, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu, or the group consisting of La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu. For example, the rare earth element RE is represented by the general formula: Y ａ Gd ｂ X ｃ ... (2) (0.05≦a≦0.9, 0.05≦b≦0.9, 0.05≦c≦0.9)

[0047] By including the Y element, the Gd element, and two or more other rare earth elements, the REBCO-based superconducting material 31 can reduce the decrease in transition temperature before and after irradiation with high-energy particles, even when used in a nuclear fusion reactor or the like that is irradiated with heavy quantum beams such as neutrons or high-energy particles. In other words, by including these elements, it is easy to realize a superconductor with excellent radiation resistance.

[0048] REBCO-based superconductors may be used in superconducting magnets for nuclear fusion reactors, and from this perspective, it is preferable to avoid the use of those with long half-lives when radioactive. Among the rare earth elements, Sm and Eu have long half-lives when radioactive compared to other rare earth elements. Therefore, it is preferable that the X element be one or more elements other than Sm and Eu, i.e., selected from the group consisting of Y, Gd, La, Ce, Pr, Nd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0049] Oxygen Storage Material The oxygen storage material 32 is, for example, YBaCo ４ O ７＋δ (δ is, for example, 1.0≦δ≦1.5) and BaLnMn ２ O ５＋δ (Ln is, for example, Pr, Nd, Sm, Gd, Dy, Er, Y, etc., and δ is, for example, 0≦δ≦1.0) and Ca ２ AlMnO ５＋δ(δ is, for example, 0≦δ≦0.5), CeO ２ , CeO ２ -ZrO ２ , TiO ２ , ZrO ２ , SnO ２ , Ta ２ O ５ , MnO ２ , Co ３ O ４ , RuO ２ , IrO ２ etc. can be used.

[0050] In general, the oxygen storage material 32 has the property of absorbing oxygen at a predetermined temperature and releasing oxygen at a higher temperature. Furthermore, oxygen atoms in the crystal structure of the REBCO-based superconducting material 31 are released when heated. The temperature range in which oxygen atoms are released from the REBCO-based superconducting material 31 is approximately 500°C or higher, although this varies slightly depending on the atoms present at the RE site. The REBCO-based superconducting material 31 and oxygen storage material 32 contained in the superconducting layer 3 preferably have a temperature range in which the oxygen storage material 32 absorbs oxygen that is equal to or higher than the temperature at which the REBCO-based superconducting material 31 releases oxygen when heated. Furthermore, the temperature range in which the REBCO-based superconducting material 31 easily absorbs oxygen is approximately above 350°C and below 500°C or below 450°C, although this varies slightly depending on the atoms present at the RE site.

[0051] The oxygen storage material 32 preferably absorbs oxygen in a temperature range below the temperature range in which the REBCO-based superconducting material 31 easily absorbs oxygen, and releases oxygen in the temperature range in which the REBCO-based superconducting material 31 easily absorbs oxygen. For example, in a TG analysis (thermogravimetric analysis) in which the REBCO-based superconducting material 31 is heated at a constant temperature for a constant time in an oxygen atmosphere, a first temperature range in which the weight ratio increases by more than +1 wt % compared to the weight at room temperature is within the temperature range below the temperature range in which the REBCO-based superconducting material 31 easily absorbs oxygen, and a second temperature range in which the weight ratio is +1 wt % or less compared to the weight at room temperature and is higher than the first temperature range is preferably used. In consideration of the temperature range in which the REBCO-based superconducting material 31 easily absorbs oxygen, for example, the first temperature range is preferably 150°C or 200°C or higher and 350°C or lower, or 300°C or lower, and the second temperature range is preferably a temperature above 350°C and 500°C or lower, or a temperature between 400°C and 450°C. For example, the oxygen storage material 32 preferably has a temperature range in which it stores oxygen in the range of 200° C. or more and 350° C. or less, and a temperature range in which it releases the stored oxygen in the range of more than 350° C. and 500° C. or less. Examples of oxygen storage materials that satisfy these characteristics include CeO ２ , YBaCo ４ O ７＋δ Examples include:

[0052] (Conductive Layer) The conductive layer 4 is located between the superconducting layer 3 and the stabilizing layer 6, and is provided in contact with the superconducting layer 3. In the example shown in Figures 1 and 2, the conductive layer 4 is provided on one surface of the superconducting layer 3. The conductive layer 4 is a layer provided to resistively heat the superconducting layer 3.

[0053] The conductive layer 4 is a metal layer having a lower resistivity than the stabilization layer 6. The resistivity of the conductive layer 4 is preferably 0.95 times or less that of the stabilization layer 6. The resistivity (Ω·m) of the conductive layer 4 can be measured by a four-terminal method. A layer made of Ag or the like can be used as the conductive layer 4. The thickness of the conductive layer 4 can be selected as desired depending on the design of the superconducting wire. In the superconducting wire, a current is selectively passed through the conductive layer 4, and the conductive layer 4 is electrically heated, thereby heating the REBCO-based superconducting material 31 and the oxygen storage material 32 in the superconducting layer 3 to a predetermined temperature for a predetermined time. As a result, oxygen atoms desorbed from the REBCO-based superconducting material 31 are absorbed by the oxygen storage material 32. At this time, it is expected that oxygen atoms will also be desorbed from the REBCO-based superconducting material 31. Furthermore, by heating the superconducting layer 3 at an even higher temperature, oxygen atoms are released from the oxygen storage material 32 and introduced into the REBCO-based superconducting material 31. Here, since a superconducting wire generally has a layer including a superconducting layer covered with a stabilizing layer or the like, gas exchange does not occur between the structure inside the stabilizing layer and the outside. Therefore, the oxygen atoms desorbed from the REBCO-based superconducting material 31 are not released to the outside, but are absorbed and released by the oxygen storage material 32 provided in contact with the REBCO-based superconducting material 31, and are thereby incorporated into the crystal structure of the REBCO-based superconducting material.

[0054] In the superconducting wire 10, oxygen atoms in the REBCO-based superconducting material 31 are emitted to the outside by high-energy ion irradiation, and as a result, the critical current density J ｃ However, in this embodiment, the oxygen storage material 32 is provided together with the REBCO-based superconducting material 31, so that the critical current density J ｃ The critical current density J of a REBCO-based superconducting material that has decreased or lost its superconductivity ｃ and the lowered superconducting transition temperature T ｃ can be improved.

[0055] (Modification) Fig. 3 is a diagram showing the configuration of a modification of the superconducting wire of the above embodiment. The superconducting wire shown in Fig. 3 differs from the superconducting wire shown in Figs. 1 and 2 in the configuration of the superconducting layer 3A in the superconducting laminate 5A and in the configuration of the oxygen storage layer 7 in contact with the superconducting layer 3A and containing an oxygen storage material 32 as a main component. In the modification, the same components as those in the above embodiment are denoted by the same reference numerals, and their description will be omitted.

[0056] The superconducting layer 3A contains a REBCO-based superconducting material 31 as a main component, and may be configured to consist of the REBCO-based superconducting material 31. In this embodiment, the main component refers to a composition whose content in the member is 50 mass % or more, preferably 90 mass % or more, and more preferably 99 mass % or more. The superconducting layer 3A may be configured to consist of the REBCO-based superconducting material 31.

[0057] The oxygen storage layer 7 may contain the oxygen storage material 32 as a main component and may be configured to consist of the oxygen storage material 32. While Fig. 3 shows a configuration in which the oxygen storage layer 7 is formed on one surface of the superconducting layer 3A in the stacking direction, the oxygen storage layer 7 may also be configured to be in contact with a side surface of the superconducting layer 3A that intersects with the one surface. For example, the oxygen storage layer 7 may be configured to surround the entire outer periphery of the superconducting laminate 5A. By increasing the contact area between the oxygen storage layer 7 and the superconducting layer 3A in this manner, oxygen desorbed from the REBCO-based superconducting material 31 can be efficiently stored by the oxygen storage material 32, released from the oxygen storage material 32 by heating, and returned to the O atomic sites of the REBCO-based superconducting material 31.

[0058] 4 is a cross-sectional view showing a configuration according to a modification of the superconducting wire of the above embodiment. As in the superconducting wire 10A shown in FIG. 4, the superconducting wire may have a configuration in which a conductive layer 4A is provided over the entire outer periphery of the superconducting laminate 5. Even in this configuration, the conductive layer 4A is configured to contact the superconducting layer 3 of the superconducting laminate 5. The configuration of the conductive layer 4A other than its cross-sectional shape can be the same as that of the conductive layer 4. The thickness of the conductive layer 4A can be the same as that of the conductive layer 4.

[0059] In the above embodiment, the superconducting wire provided with the conductive layers 4, 4A has been described, but the superconducting wire of the present invention is not limited to this example. A superconducting wire according to one embodiment of the present invention may be configured not to provide the conductive layers 4, 4A, but to heat the superconducting layer 3 by resistance heating by passing a current through the first stabilization layer 6a, which is the stabilization layer 6 in contact with the superconducting layer 3.

[0060] [Method for Repairing Copper Oxide Superconductor] The copper oxide superconductor according to the above embodiment can be repaired by the following method. The repair method according to this embodiment includes a heating step. In the heating step, the copper oxide superconductor is heated to induce oxygen diffusion from the oxygen storage material 32 to the REBCO superconducting material 31, thereby repairing oxygen vacancies in the REBCO superconducting material 31. That is, after the heating step, a reaction occurs such that the positions of oxygen atoms in the copper oxide superconductor return to the positions they were in before irradiation with neutron beams or the like, and the copper oxide superconductor is repaired.

[0061] The heating step is typically carried out in an environment where there is no exchange of gas with the outside, for example, by forming layers to surround the copper oxide-based superconductor. For example, in the superconducting wire according to the above embodiment, the superconducting laminate 5 including the superconducting layer 3 is surrounded by the stabilization layer 6, thereby creating an environment where there is no exchange of gas with the outside. Therefore, oxygen must be supplied to the REBCO-based superconducting material 31 from a member provided in the same space (hereinafter referred to as a closed space) that is separated from the outside. Furthermore, from the viewpoint of efficient heating of the copper oxide, it is preferable that a member for heating the copper oxide-based superconductor is also provided in the closed space.

[0062] In the superconducting laminate 5 according to the above embodiment, when the copper oxide superconductor is repaired, the superconducting layer 3 may be heated by applying an electric current to the conductive layer 4, or the superconducting layer 3 may be heated by applying a voltage to the superconducting layer 3 itself and directly passing an electric current through it. In the heating step, the copper oxide superconductor is preferably heated at a temperature of 150°C or higher and 500°C or lower, more preferably at a temperature higher than 350°C and 450°C or lower, and even more preferably at a temperature of 300°C or higher and 400°C or lower, although this can be adjusted appropriately depending on the material.

[0063] CeO as an oxygen storage material ２ When using CeO ２ In order to release oxygen from the oxygen storage material, the heating temperature is preferably 380°C or higher, more preferably 400°C or higher, and may be 420°C or higher, but is preferably 500°C or lower. ４ O ７＋δ When using the above, for the same reason, the heating temperature is preferably 400° C. or higher and 600° C. or lower, and more preferably 400° C. or higher and 450° C. or lower.

[0064] The heating time in the heating step is 30 minutes or more, and preferably 1 hour or more. Although heating the copper oxide-based superconductor does not immediately compensate for oxygen diffusion from the oxygen storage material 32 or oxygen deficiency in the REBCO-based superconducting material 31, the heating time mentioned above sufficiently repairs the copper oxide-based superconducting material and reduces the critical current density J lowered by irradiation. ｃ and the superconducting transition temperature T ｃ The heating time in the heating step is not particularly limited, but it is preferable to set it within a certain time from the viewpoint of efficiency, since the effect of heating on the repair of the copper oxide-based superconductor is thought to saturate. The heating time in the heating step can be adjusted appropriately depending on the type of copper oxide-based superconductor to be heated, the content of the oxygen storage material, the degree of oxygen deficiency, etc., but can be, for example, 4 hours or less or 24 hours or less.

[0065] Furthermore, in the method for repairing a copper oxide superconductor according to this embodiment, the heating step may be configured to include a first step of heating the copper oxide superconductor at a low first temperature within the above temperature range, and a second step of heating the copper oxide superconductor at a second temperature higher than the first temperature.

[0066] The first step is a step of causing oxygen dispersed around the copper oxide-based superconductor during film formation in an oxygen atmosphere and oxygen released from the REBCO-based superconducting material 31 to be absorbed into the oxygen storage material 32, and the second step is a step of releasing oxygen from the oxygen storage material 32 and returning it to the REBCO-based superconducting material.

[0067] The first temperature and the second temperature can be adjusted, for example, depending on the oxygen storage material 32 used. The first temperature is preferably set within a temperature range where the weight ratio of the oxygen storage material 32 to the weight of the oxygen storage material at room temperature increases in a TG analysis, which measures the weight when heated at a predetermined temperature for a certain period of time in an oxygen atmosphere. For example, the first temperature is preferably set to a temperature where the weight ratio exceeds +1 wt %. As an example, the first temperature is preferably set to a temperature between 150°C and 350°C, and may be set to a temperature between 200°C and 300°C. The second temperature is a temperature higher than the first temperature. The second temperature is preferably set within a temperature range where the weight is lower than the weight at the first temperature in the TG analysis, more preferably a temperature where the weight at room temperature is +1 wt % or less. It is even more preferable that the second temperature be a temperature where the REBCO-based superconducting material 31 has a high oxygen absorption efficiency, i.e., a temperature where the weight gain rate is high in a thermogravimetric analysis under an oxygen atmosphere. From this perspective, the second temperature in the second step is preferably set to 500°C or less, or a temperature between 350°C and 450°C. The second step may be performed at a temperature of 350° C. or higher and 420° C. or lower. Examples of oxygen storage materials suitable for the first and second temperatures include CeO ２ , YBaCo ４ O ７＋δ In this embodiment, it is preferable to use these oxygen storage materials. The time for each of the first step and the second step is preferably 15 minutes or more, more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the time for each of the first step and the second step is not particularly limited, but may be 2 hours or less from the viewpoint of efficiency.

[0068] Between the first and second steps, the copper oxide superconductor may be cooled, or may be heated without cooling. The heating step does not need to be divided into the first and second steps; oxygen is absorbed into the oxygen storage material 32 during the heating process up to a temperature corresponding to the second temperature, and then released at a higher temperature. Therefore, there is no need to go through a process of maintaining the temperature lower than the second temperature for a certain period of time. However, by dividing the heating step into the first and second steps and maintaining each step for a certain period of time, the flow of oxygen between the REBCO superconducting material and the oxygen storage material can be more precisely controlled. During the heating step, the temperature may be changed over time as appropriate within a predetermined temperature range.

[0069] [Method for Manufacturing Superconducting Wire] A method for manufacturing a superconducting wire according to one embodiment of the present invention will be described below, taking as an example a method for manufacturing the superconducting stack wire shown in Figures 1 and 2. The method for manufacturing a superconductor according to one embodiment of the present invention includes a preparation step of preparing an underlayer 12 whose surface is made of a single crystal, and a deposition step of depositing a superconductor on the underlayer 12. When manufacturing a superconducting wire in which layers are stacked in the radial direction, it is preferable to form each layer continuously using, for example, a reel-to-reel type manufacturing device. When manufacturing a superconducting laminate in which layers are stacked in a direction perpendicular to the underlayer 12, it is preferable to form each layer continuously using a roll-to-roll type manufacturing device.

[0070] (Preparation Step) First, an underlayer 12 having a surface made of a single crystal is prepared. The underlayer 12 is made of, for example, a substrate 1 and an intermediate layer 2. The intermediate layer 2 can be formed on the substrate 1 by, for example, physical vapor deposition such as PLD, or vapor deposition such as chemical vapor deposition, or by baking. In the preparation step, for example, a process is performed so that at least one surface of the underlayer 12 and its vicinity are made of a single crystal. For example, the preparation step is performed a predetermined number of times depending on the number of layers that make up the intermediate layer 2 to be formed.

[0071] (Target Preparation Step) Next, a target to be used in the vapor deposition step is prepared. For example, a target can be formed by mixing raw materials for a REBCO-based superconducting material and raw materials for an oxygen storage material in a predetermined mixing ratio and firing the mixture. The target is formed by mixing and sintering a composition corresponding to the composition of the desired REBCO-based superconducting material and a composition corresponding to the composition of the desired oxygen storage material. In other words, the composition of each material can be the same as that of the superconducting wire according to the above embodiment. Known methods can be used as the mixing and sintering method for producing the target.

[0072] The raw material for a REBCO-based superconducting material is, for example, a material obtained by mixing predetermined metal element simple substances or oxides in a predetermined ratio and firing the mixture. That is, a powder of simple substances or oxides containing a predetermined rare earth element, Ba, and Cu is fired. The oxygen storage material is a material obtained by firing a predetermined metal element simple substance or oxide. When the oxygen storage material contains multiple metal elements, the oxygen storage material is formed by mixing and firing multiple metal element simple substances or oxides. The firing of the oxygen storage material and the REBCO-based superconducting material is performed by secondary firing.

[0073] The mixing ratio of the raw material for the oxygen storage material to the raw material for the REBCO-based superconducting material and the raw material for the oxygen storage material in the target preparation step can be the same as the content of the oxygen storage material 32 in the superconducting layer 3 .

[0074] (Vapor Deposition Step) Next, a superconductor is vapor-deposited on the underlayer 12. The vapor deposition step is performed by a physical vapor deposition (PVD) method such as a pulsed laser deposition (PLD) method, a molecular beam epitaxy (MBE) method, or a sputtering method. In the vapor deposition step, it is preferable to place a target T in a position facing the underlayer 12 and irradiate the target T with a laser.

[0075] FIG. 5 is a diagram illustrating a method for manufacturing a superconductor according to one embodiment of the present invention, showing a state in which a vapor deposition process is performed by the PLD method. The PLD method will be described with reference to FIG. 5. The PLD method is performed using a PLD apparatus. The target T and the underlayer 12 prepared in the target preparation process are placed facing each other in the chamber of the PLD apparatus. The atmosphere in the chamber can be, for example, an oxygen atmosphere, a mixed atmosphere of oxygen and an inert gas, or the like. The vapor deposition process is performed, for example, by adjusting the chamber to have a low oxygen partial pressure and heating the underlayer 12.

[0076] The oxygen partial pressure in the chamber is, for example, 1×10 －５ The temperature (set temperature) T of the underlayer 12 can be set to 1 Pa or more and 50 Pa or less, and is preferably set to 1 Pa or more and 20 Pa or less. ｓ The heating temperature can be adjusted to, for example, 200°C or higher and 1000°C or lower.

[0077] The PLD device irradiates a target T with laser light L and focuses the laser light L on the surface of the target T using a focusing lens or the like. A pulsed laser is used as the laser light L irradiated onto the target T. The laser density is, for example, 0.1 J / cm. ２ 5J / cm or more ２ Do the following:

[0078] By focusing a laser on the surface of the target T, constituent particles of the target T are knocked out or evaporated, generating a plume P. The constituent particles of the target T contained in the plume P are deposited on the surface of the base layer 12, thereby forming a thin film composed of the constituent particles of the target T on the surface of the base layer 12. Therefore, the composition of the thin film formed on the base layer 12 can be changed by changing the composition of the constituent particles of the target T. In other words, when a superconductor of a desired composition is to be formed on the base layer 12, it is sufficient to use a target T having the same composition as the desired superconductor.

[0079] In the vapor deposition process, the temperature of the atmosphere to which the underlayer 12 is exposed is, for example, from 0° C. to 1,000° C., and preferably from 30° C. to 300° C. The temperature can be confirmed by measuring the temperature inside a chamber in which the vapor deposition process is carried out.

[0080] (Annealing Step) The method for manufacturing a superconducting laminate according to this embodiment may further include an annealing step of annealing the superconducting layer 3 formed by the vapor deposition step. In the annealing step, for example, a laminate in which the superconducting layer 3 is formed on the underlayer 12 is heated in an oxygen atmosphere at 1 atmosphere or less. In this embodiment, the oxygen atmosphere is not limited to an atmosphere consisting of oxygen, but may also be an atmosphere containing other inert gases. In the oxygen atmosphere, the oxygen partial pressure is at least half of the total pressure, and preferably at least 90% of the total pressure. The heating temperature of the laminate in the annealing step may be, for example, 300°C to 500°C, and preferably 350°C to 400°C. The heating temperature of the laminate in the annealing step may be, for example, 300°C to 500°C, and preferably 1 hour to 5 hours.

[0081] (Conductive Layer Forming Step) After the formation of the superconducting layer 3, the conductive layer 4 is formed in contact with the superconducting layer 3 by vapor deposition or the like. The conductive layer 4 can be formed by a known method for forming a thin film of a simple metal, such as a vapor deposition method, a sputtering method, or a chemical vapor deposition method. The conductive layer forming step may be performed before or after the annealing step.

[0082] The method for manufacturing a superconducting wire according to this embodiment further includes a stabilization layer forming step of providing a stabilization layer 6 by a known method before or after the annealing step.

[0083] The above-described method can be used to fabricate superconducting wires as shown in FIGS. 1 and 2 . When forming a superconducting wire as shown in FIG. 3 , first, in the target preparation step, a target is prepared by mixing and firing only REBCO-based superconducting material powder without mixing any raw materials for the oxygen storage material, and a deposition step is performed using the target. Next, the oxygen storage layer 7 is formed. The oxygen storage layer 7 can be formed by a known method for forming a layer whose main component is an oxygen storage material. For example, the raw materials for the oxygen storage material are mixed and fired to prepare a target for the oxygen storage layer, and the oxygen storage layer can be formed by a PLD method using the target. When forming a superconducting wire as shown in FIG. 4 , in the conductive layer formation step, the thin film formation method can be adjusted so as to surround the outer periphery of the superconducting laminate 5.

[0084] As described above, the copper oxide-based superconductor according to one embodiment of the present invention is a superconductor having a structure in which an oxygen storage material (oxygen storage / release material) is introduced into a layer of a REBCO-based superconducting material, or is introduced into a REBCO-based superconducting material by a structure in which the material is laminated with a layer mainly composed of a REBCO-based superconducting material, or is arranged so as to be in contact with the REBCO-based superconducting material. With such a structure, oxygen vacancies generated in the REBCO-based superconducting material by irradiation of neutrons or the like are repaired by oxygen release / diffusion from the oxygen storage material, and the superconducting transition temperature T c This technology restores superconducting properties such as the above (Figure 2).

[0085] The superconducting layer 3 or the oxygen storage layer 7 containing the oxygen storage / release material is heated by a heater by passing current through the adjacent conductive layer or by heating the superconducting wire itself. 7+δ , BaLnMnO 5+δ , Ca2AlMnO 5+δ In addition to the above materials, oxides such as CeO2, CeO2-ZrO2, TiO2, ZrO2, SnO2, Ta2O5, MnO2, Co3O4, RuO2, and IrO2, as well as SrFeO3 and BaFeO 3-dIt is possible to use oxygen storage and release materials such as iron-based oxides with related structures having a perovskite structure, such as those described above, iron-based oxides with related chemical compositions, and other common transition metal oxides such as α-Fe2O3. In addition, oxygen storage and release materials may be used as artificial pinning centers for magnetic flux, and from this perspective, it is possible to use oxygen storage and release materials that have a critical current density J both before and after irradiation with neutrons, etc. ｃ It is also thought that this will help improve

[0086] In one embodiment of the present invention, the oxygen storage and release material is a REBCO-based superconducting material REBa2Cu3O 7- This invention proposes a method for repairing oxygen vacancies in a REBCO-based superconducting material after irradiation with ions, neutrons, or the like, by oxygen diffusion from the oxygen storage material, by stacking the oxygen storage material on a superconducting layer 3A mainly composed of x or introducing the oxygen storage material into the superconducting layer 3. As the rare earth element RE in the REBCO-based superconducting material, one or more elements selected from the group consisting of Sr, Ba, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu are used, and a high-entropy REBCO-based superconductor containing three or more rare earth elements RE can also be used.

[0087] YBaCoO 7+δ , BaLnMnO 5+δ and CaAlMnO 5+δ By using oxygen absorbing (storing) materials such as these, oxygen diffusion can be induced to oxygen vacancy sites in REBCO superconductors that have been created by irradiation with neutrons or other beams (Figure 2), and the superconducting transition temperature Tc can be expected to be restored by repairing the oxygen vacancies. In addition, by introducing non-superconducting oxygen absorbing materials into the superconducting layer as pinning centers for artificial magnetic fields, it is expected that radiation resistance will be improved and a pinning effect against magnetic fields will be achieved.

[0088] Differences from the Prior Art In one embodiment of the present invention, an oxygen storage material is thinned as an oxygen source for repairing oxygen vacancies in a REBCO-based superconducting material in a copper oxide-based superconductor, and then the REBCO-based superconducting material REBa2Cu3O 7-xor precipitated in the superconducting layer 3. The method for repairing a copper oxide-based superconducting material differs from the technical concept and configuration of the prior art in that an oxygen storage material provided in contact with the REBCO-based superconducting material is utilized as an oxygen source that compensates for oxygen deficiencies after irradiation with ions, neutrons, or the like by low-temperature heat treatment (heating step).

[0089] In one embodiment of the present invention, by depositing an oxygen storage material on the superconductor or depositing it within the superconductor, oxygen is diffused from the oxygen storage material by heat treatment, which is expected to repair (complement) oxygen deficiency in the copper oxide high-temperature superconductor after irradiation. Furthermore, the oxygen storage material 32 is expected to function as an artificial pinning center against magnetic fields, which is also believed to be effective in improving superconducting properties in high magnetic fields.

[0090] Key Points: REBa2Cu3O 7-ｘ The oxygen storage material is used as an oxygen source to compensate for oxygen deficiency after irradiation of REBCO-based superconducting materials such as those described above with ions or neutrons. By heating the material after irradiation, oxygen release from the oxygen storage material 32 is induced, which compensates for the oxygen deficiency in the REBCO-based superconducting material and restores the superconducting transition temperature Tc. By introducing the oxygen storage material into the superconductor, it can be used as an artificial pinning center against magnetic fields.

[0091] When a copper oxide-based superconductor in which oxygen has been lost from a REBCO-based superconducting material by irradiation with high-energy ions, neutrons, etc. is to be repaired, oxygen diffusion from the oxygen storage material to the copper oxide-based superconductor can be induced by heating the copper oxide-based superconductor. For example, a conductive layer can be provided in contact with the copper oxide-based superconductor, and electricity can be passed through the conductive layer.

[0092] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various omissions, substitutions, modifications, and alterations are possible within the scope of the gist of the present invention as set forth in the claims. For example, the inventions relating to copper oxide-based superconductors, methods for manufacturing copper oxide-based superconductors, and methods for repairing copper oxide-based superconductors are not limited to the content described in each embodiment, and can be appropriately combined based on the content described in each embodiment. For example, the oxygen storage material described in the embodiment relating to the method for repairing copper oxide-based superconductors may be applied to the invention of copper oxide-based superconductors. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

[0093] The upper and / or lower limits of the numerical ranges described herein can be arbitrarily combined to define a preferred range. For example, the upper and lower limits of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limits of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limits of the numerical ranges can be arbitrarily combined to define a preferred range.

[0094] Throughout this disclosure, singular terms should be understood to include the plural concept unless otherwise specified. Thus, singular articles (e.g., "a," "an," "the," etc. in English) should be understood to include the plural concept unless otherwise specified.

[0095] [Example 1] A REBCO-based superconducting material (YBa ２ Cu ３ O ７－ｘ ) and oxygen storage material CeO ２ A superconducting laminate was fabricated in which a superconducting layer containing CeO ２Nanorods are oxygen storage materials that exhibit a thermal weight gain of approximately 3 wt% from 200 to 300°C and a thermal weight loss of approximately 3 wt% from 380 to 450°C in TG analysis under an oxygen atmosphere (M. Karppinen et al., Chem. Mater., 18, No. 2 (2006)).

[0096] First, the underlayer was prepared. ３ A single crystal substrate was prepared.

[0097] Next, to prepare targets, raw materials for the REBCO-based superconducting material and raw materials for the oxygen storage material were prepared. Specifically, as the raw materials for the REBCO-based superconducting material, Y2O3 (purity 99.9%), BaCO3 (purity 98%), and CuO (purity 99.9%) were weighed out in a material ratio of 1:2:3 and mixed in a mortar to prepare a mixed powder. The mixture was then fired in air at 930°C for 20 hours, returned to room temperature, and then fired at 930°C for 8 hours (secondary firing), followed by annealing at 350°C for 18 hours. In this way, the secondary firing in Example 1 was performed at the same temperature. In addition, CeO was used as the powder for the oxygen storage material. ２ CeO2 (manufactured by Kojundo Chemical Laboratory, product name: CeO2, purity: 99.9%, shape: powder, product number: CE004PB, rod number: Lot. 4101701) was prepared. These were then mixed and fired in air at 930°C for 20 hours, then fired at 930°C for 8 hours, and annealed in air at 350°C for 18 hours to produce a target. In this example, the weight ratio of the raw material for the REBCO-based superconducting material in the target was 80 wt%, and the weight ratio of the powder for the oxygen storage material was 20 wt%.

[0098] Next, in the PLD device, the underlayer and the target were placed in a chamber so that they faced each other. Next, a rotary pump was used to evacuate the chamber until the oxygen partial pressure inside the chamber reached 20 Pa. In addition, the underlayer was heated using a heater to a heating temperature T ｓ The heating temperature T ｓ After reaching this temperature, it was left to stand for 10 minutes to stabilize.

[0099] To remove impurities from the target surface, the shutter was closed and the target was pre-ablated. Then, a superconducting layer was formed by PLD under the following film formation conditions: (Film formation conditions) Heating temperature T of the base layer s : 720℃ (Set temperature SV: 894℃) Film formation time: 40 min Oxygen partial pressure in the chamber: 20 Pa Laser pulse frequency: 5 Hz Laser input power: 55 J Laser output power: 290 mJ

[0100] (X-ray Diffraction) X-ray diffraction was performed on the superconducting layer formed on the underlayer in Example 1. FIG.

[0101] (Superconducting transition temperature measurement) For the structure of Example 1, the temperature dependence of the magnetization of the superconductor was measured using a magnetic property measurement system (MPMS-3). Figure 7(a) is a graph of the temperature dependence of the magnetization of the structure of Example 1, and Figure 7(b) is an enlarged view of a partial area of ​​Figure 7(a). The superconducting transition temperature T ｃ The superconducting transition temperature T ｃ is the temperature at which the magnetization begins to drop during zero field cooling (ZFC).

[0102] (Critical Current Density Test) The critical current density of the structure of Example 1 was measured using a magnetic property measurement system (MPMS-3) under temperature environments of 4.2K, 20K, and 50K while varying the external magnetic field.

[0103] Fig. 8 is a graph showing the magnetic field dependence for each temperature of the critical current density of the structure of Example 1. As can be seen from Fig. 8, it was confirmed that superconductivity was exhibited even when a target in which a raw material for a REBCO-based superconducting material and a raw material for an oxide-based superconducting material were mixed was used as in Example 1 and a superconducting layer composed of a REBCO-based superconducting material and an oxygen storage material was formed on an underlayer.

[0104] (Irradiation Resistance Test) The structure of Example 1 was irradiated with Ar ions so as to cause damage comparable to that caused by neutron irradiation. FIG. 9 is a graph showing the temperature dependence of magnetization after the ion irradiation test for the structure of Example 1. As shown in FIG. 9, the ion irradiation test confirmed that the superconductivity in the superconducting layer of the structure confirmed in FIG. 7 had disappeared. This suggests that high-energy ion irradiation caused oxygen to be desorbed from the REBCO-based superconducting material in the superconducting layer, resulting in the disappearance of superconductivity due to oxygen deficiency. In the sample of Example 1, the conductive layer was provided in contact with one surface of the superconducting layer, rather than surrounding the entire outer periphery of the structure, and no stabilization layer was formed. Therefore, it was difficult to control the movement of gas inside and outside the structure. However, it is believed that heating the superconducting layer in an environment where there is substantially no movement of gas inside and outside the structure can repair the copper oxide-based superconductor, i.e., supplement oxygen to fill in the oxygen deficiency in the REBCO-based superconducting material.

[0105] The present invention improves the radiation resistance of superconducting materials, contributing to the extension of the life of fusion reactors.

[0106] REFERENCE SIGNS LIST 1 substrate 2 intermediate layer 2a first intermediate layer 2b second intermediate layer 2c third intermediate layer 3, 3A superconducting layer 4, 4A conductive layer 5, 5A superconducting laminate 6 stabilizing layer 6a first stabilizing layer 6b second stabilizing layer 7 oxygen storage layer 10, 10A superconducting wire 12 underlayer 31 REBCO-based superconducting material 32 oxygen storage material L laser light P plume RE rare earth element T target

Claims

1. REBa, which contains a REBCO-based superconducting material represented by general formula (1) and an oxygen storage material. ２ Cu ３ O ７－ｘ ...(1) Copper oxide superconductor (In formula (1), RE is composed of one or more elements selected from the group consisting of Sr, Ba, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and satisfies 0≦x≦1).

2. A REBCO-based superconducting material represented by general formula (1) and REBa ２ Cu ３ O ７－ｘ ...(1) A copper oxide-based superconductor comprising: an oxygen storage material provided in contact with the REBCO-based superconducting material (in formula (1), RE is composed of one or more elements selected from the group consisting of Sr, Ba, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and satisfies 0≦x≦1).

3. The oxygen storage material is YBaCo ４ O ７＋δ and BaLnMn ２ O ５＋δ and Ca ２ AlMnO ５＋δ 3. The copper oxide superconductor according to claim 1, wherein δ is any one selected from the group consisting of:

4. The oxygen storage material is CeO ２ and CeO ２ -ZrO ２ and TiO ２ and ZrO ２ and SnO ２ And, Ta ２ O ５ and MnO ２ And Co ３ O ４ and RuO ２ and IrO ２ 3. The copper oxide superconductor according to claim 1, wherein the copper oxide superconductor is one or more selected from the group consisting of:

5. The copper oxide superconductor according to claim 1 or 2, wherein the oxygen storage material is an iron-based oxide having a perovskite structure.

6. The oxygen storage material is α-Fe ２ O ３ 3. The copper oxide superconductor according to claim 1, wherein 7. The copper oxide superconductor according to claim 1 or 2, wherein in the REBCO-based superconducting material, in general formula (1), RE is composed of one or more elements selected from the group consisting of Y, Gd, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

8. The copper oxide superconductor according to claim 7, wherein RE in the above formula (1) is composed of four or more rare earth elements.

9. The copper oxide superconductor according to claim 7, wherein in the above formula (1), RE is composed of Y, Gd, and X, and X is composed of one or more elements selected from the group consisting of Sr, Ba, Ca, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

10. The copper oxide superconductor Y according to claim 7, wherein in the formula (1), RE is represented by the general formula (2): ａ Gd ｂ X ｃ ... (2) (0.05≦a≦0.9, 0.05≦b≦0.9, 0.05≦c≦0.9).

11. In the above formula (1), RE is composed of five or more rare earth elements, and the mixing entropy ΔS of the RE site is ｍｉｘ 8. The copper oxide superconductor according to claim 7, wherein R is 1.4R or more.

12. The copper oxide superconductor according to claim 1, wherein the content of the oxygen storage material is greater than 0 wt % and not more than 90 wt %.

13. The copper oxide superconductor according to claim 1, wherein the oxygen storage material has a temperature range in which it stores oxygen in the range of 200°C or higher and 350°C or lower, and a temperature range in which it releases the stored oxygen in the range of more than 350°C and 500°C or lower.

14. A superconducting wire comprising: a superconducting laminate having an underlayer and a superconducting layer formed on the underlayer and containing the copper oxide-based superconductor according to claim 1; a stabilizing layer surrounding the outer periphery of the superconducting laminate; and a conducting layer located between the superconducting laminate and the stabilizing layer and in contact with the superconducting layer.

15. A method for repairing a copper oxide-based superconductor, comprising a heating step of heating the copper oxide-based superconductor according to claim 1 or 2, inducing oxygen diffusion from the oxygen storage material to the REBCO-based superconducting material, and repairing oxygen vacancies in the REBCO-based superconducting material.

16. A method for repairing a copper oxide superconductor according to claim 15, wherein the copper oxide superconductor is heated at a temperature of 150°C or higher and 500°C or lower in the heating step.

17. A method for repairing a copper oxide superconductor using a superconducting wire comprising: a wire made of a copper oxide superconductor; a stabilizing layer surrounding the outer periphery of the wire; and a conductive layer located between the wire and the stabilizing layer and in contact with the copper oxide superconductor, wherein the conductive layer is heated by passing electricity through it in the heating step.

18. A method for repairing a copper oxide superconductor according to claim 16, wherein the heating step comprises a first step of heating the copper oxide superconductor at a first temperature of 150°C or higher, and a second step of heating the copper oxide superconductor at a second temperature higher than the first temperature and not higher than 500°C.

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