Superconducting wire rod and method for manufacturing superconducting wire rod

Abstract

A superconducting wire rod according to the present invention has a superconducting layer containing REBa2Cu3Ox. RE is a rare earth element. The superconducting layer contains halogen. The concentration of halogen in the superconducting layer is less than 2000 ppm by mass.

Description

Technical Field

[0001] The present invention relates to a superconducting wire and a method for manufacturing a superconducting wire. This application claims priority to Japanese patent application No. 2023-040888 filed on March 15, 2023. All the contents described in the Japanese patent application are incorporated into this specification by reference. Background Art

[0002] Japanese Patent Publication No. 2015-106521 (Patent Document 1) describes a superconducting wire. The superconducting wire described in Patent Document 1 includes a metal substrate, an intermediate layer arranged on the metal substrate, and an oxide superconducting film arranged on the intermediate layer. The constituent material of the oxide superconducting film is REBa 2 Cu 3 O x (RE is a rare earth element). The oxide superconducting film has a 2 Cu 3 O x The crystals are oriented in the c-axis direction.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-106521. Summary of the invention

[0006] The superconducting wire of the present invention has a 2 Cu 3 O x (RE is a rare earth element). The superconducting layer contains halogen. The concentration of the halogen in the superconducting layer is less than 2000 mass ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a cross-sectional view of superconducting wire 100 .

[0008] Figure 2 2 is a process diagram showing a method for manufacturing superconducting wire 100 .

[0009] Figure 3 It is a cross-sectional view explaining the preparation step S1.

[0010] Figure 4 It is a cross-sectional view for explaining the intermediate layer forming step S2.

[0011] Figure 5 It is a cross-sectional view for explaining the solution coating step S3.

[0012] Figure 6 It is a cross-sectional view explaining the first firing step S4.

[0013] Figure 7 It is a cross-sectional view explaining the second firing step S5. DETAILED DESCRIPTION

[0014] [Problems to be Solved by the Invention]

[0015] In the superconducting wire described in Patent Document 1, the oxide superconducting film is formed by the following method. First, a raw material solution is prepared. The raw material solution contains the constituent elements of the oxide superconducting film and chlorine. Second, the raw material solution is applied to the intermediate layer. Third, a first sintering is performed. Thus, Ba 2 Cu 3 O 4 Cl 4 Fourth, the second firing is performed. Thus, REBa 2 Cu 3 O x Crystals of Ba are generated on the intermediate layer and grow while being oriented in a specific crystal direction, thereby forming an oxide superconducting film. 2 Cu 3 O 4 Cl 4 Helps make REBa 2 Cu 3 O x of crystal orientation.

[0016] In the superconducting wire described in Patent Document 1, the raw material solution contains chlorine, and therefore the oxide superconductor film contains chlorine. Chlorine in the oxide superconductor film may become a chlorine that destroys REBa. 2 Cu 3 O x The composition balance or the reason for the reduction in volume of the oxide superconductor film.

[0017] The present invention has been made in view of the above-mentioned prior art and provides a superconducting wire having a reduced halogen concentration in a superconducting layer.

[0018] [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a superconducting wire having a reduced halogen concentration in a superconducting layer.

[0020] [Description of Embodiments of the Invention]

[0021] First, embodiments of the present invention are listed and described for explanation.

[0022] (1) A superconducting wire according to one embodiment has a 2 Cu 3 O xThe superconducting layer includes a halogen. The concentration of the halogen in the superconducting layer is less than 2000 mass ppm. According to the superconducting wire of (1) above, the REBa contained in the superconducting layer can be suppressed. 2 Cu 3 O x The composition balance is destroyed and the volume of the superconducting layer is reduced.

[0023] (2) In the superconducting wire of (1) above, the concentration of the halogen in the superconducting layer may be 2 mass ppm or more.

[0024] (3) In the superconducting wire of (1) or (2) above, the halogen may be chlorine.

[0025] (4) In the superconducting wire according to any one of (1) to (3) above, the superconducting layer may contain an alkali metal. The concentration of the alkali metal in the superconducting layer may be 1 ppb by mass or more.

[0026] (5) In the superconducting wire of (4) above, the alkali metal may be sodium.

[0027] (6) The superconducting wire of any one of (1) to (5) above may further include a substrate and an intermediate layer disposed on the substrate. The superconducting layer may include a first main surface and a second main surface opposite to the first main surface. The superconducting layer may be disposed on the intermediate layer in such a manner that the first main surface and the intermediate layer face each other. The Ba of the second main surface 2 Cu 3 O 4 X 2 The precipitation amount can be greater than that of Ba in the superconducting layer. 2 Cu 3 O 4 X 2 The amount of precipitation is large. X is a halogen.

[0028] (7) A method for manufacturing a superconducting wire according to one embodiment includes forming a superconducting wire having a structure of REBa on an intermediate layer disposed on a substrate. 2 Cu 3 O x RE is a rare earth element. The process of forming a superconducting layer includes: a process of applying a solution containing a constituent element of the superconducting layer on the intermediate layer; a process of making a precursor of the superconducting layer by heating the applied solution; and a process of making the precursor into a superconducting layer by heating the precursor. The solution contains a halogen. At least one of the solution, the precursor, and the atmosphere when the precursor is heated contains an alkali metal. According to the method for manufacturing a superconducting wire of the above (7), the concentration of halogen in the superconducting layer can be reduced.

[0029] (8) In the method for producing a superconducting wire according to (7) above, the concentration of the alkali metal in the solution may be 1 ppb by mass or more.

[0030] (9) In the method for producing a superconducting wire according to (7) above, the partial pressure of the alkali metal in the atmosphere may be 1000 Pa or less.

[0031] (10) In the method for producing a superconducting wire according to any one of (7) to (9) above, the halogen may be chlorine.

[0032] (11) In the method for producing a superconducting wire according to any one of (7) to (10) above, the alkali metal may be sodium.

[0033] [Details of the embodiments of the present invention]

[0034] Next, refer to the attached Figure 1 In the following drawings, the same or corresponding parts are given the same reference numerals, and repeated descriptions are not repeated. The superconducting wire of the embodiment is referred to as superconducting wire 100.

[0035] (Configuration of Superconducting Wire 100)

[0036] Below, refer to Figure 1 The structure of superconducting wire 100 will be described.

[0037] like Figure 1 As shown, the superconducting wire 100 has a substrate 10, an intermediate layer 20 and a superconducting layer 30. The superconducting wire 100 may also have a protective layer and a stabilizing layer. In this case, the constituent material of the protective layer is, for example, silver or a silver alloy, and the constituent material of the stabilizing layer is, for example, copper or a copper alloy. The protective layer is disposed on the superconducting layer 30. The stabilizing layer is disposed on the protective layer.

[0038] The substrate 10 has a main surface 10a and a main surface 10b. The main surface 10a and the main surface 10b are end surfaces in the thickness direction of the substrate 10. The main surface 10b is opposite to the main surface 10a.

[0039] The substrate 10 is, for example, a coating material having a stainless steel strip member, a copper (Cu) layer disposed on the strip member, and a nickel (Ni) layer disposed on the copper layer. The crystal axis of the copper layer is oriented. The crystal axis of the nickel layer is also oriented along the crystal axis of the copper layer. In addition, the nickel layer constitutes the main surface 10a. The substrate 10 is not limited to the above-mentioned coating material, and may also be a material other than the coating material. The substrate 10 may be, for example, Hastelloy (registered trademark). The substrate 10 may also be a strip member composed of a biaxially oriented metal material or a strip member composed of a non-oriented metal material.

[0040] The intermediate layer 20 has a main surface 20a and a main surface 20b. The main surface 20a and the main surface 20b are end surfaces in the thickness direction of the intermediate layer 20. The intermediate layer 20 is arranged on the substrate 10 so that the main surface 20a faces the main surface 10a (the main surface 20a faces the main surface 10a).

[0041] The intermediate layer 20 has, for example, yttrium oxide (Y 2 O 3 ) layer, a yttria-stabilized zirconia (YSZ) layer disposed on the yttria layer, and a cerium oxide (CeO 2 ) layer. The layer structure of the intermediate layer 20 is not limited thereto. As described above, the crystal axis of the nickel layer of the substrate 10 is oriented, and therefore, the crystal axis of each layer of the intermediate layer 20 is also oriented. The intermediate layer 20 may be a double-layer structure or a single-layer structure.

[0042] The superconducting layer 30 is disposed on the intermediate layer 20 (the main surface 20b). As described above, the crystal axis of the intermediate layer 20 is oriented, and therefore the c-axis, which is the crystal axis of the superconducting layer 30, is also oriented along the crystal axis of the intermediate layer 20. Typically, the superconducting layer 30 is formed of a material (REBa to be described later) 2 Cu 3 O x ) is oriented in a manner that the c-axis of the crystal is along the normal direction of the main surface 20b. Here, "oriented in a manner that ... the c-axis is along the normal direction of the main surface 20b" means that the inclination angle of the c-axis relative to the normal direction of the main surface 20b is within 15°. The superconducting layer 30 has a main surface 30a and a main surface 30b. The main surface 30a and the main surface 30b are end surfaces of the superconducting layer 30 in the thickness direction. The main surface 30a faces the intermediate layer 20 (main surface 20b). The main surface 30b is opposite to the main surface 30a.

[0043] The constituent material of the superconducting layer 30 is REBa 2 Cu 3 O x . Here, RE is a rare earth element. Rare earth elements are, for example, gadolinium (Gd), yttrium (Y), and europium (Eu). However, rare earth elements are not limited to these. The superconducting layer 30 contains halogen. Halogen is, for example, chlorine (Cl). However, halogen is not limited to this. The superconducting layer 30 may contain an alkali metal. Alkali metal is, for example, sodium (Na). However, alkali metal is not limited to this. Alkali metal may not be contained in the superconducting layer 30.

[0044] The concentration of halogen in the superconducting layer 30 is less than 2000 mass ppm. The concentration of halogen in the superconducting layer 30 may be 1800 mass ppm or less, or 1500 mass ppm or less. The concentration of halogen in the superconducting layer 30 is, for example, 2 mass ppm or more. The concentration of alkali metal in the superconducting layer 30 is, for example, 2000 mass ppm or less. The concentration of alkali metal in the superconducting layer 30 is, for example, 1 mass ppb or more. The concentration of halogen in the superconducting layer 30 and the concentration of alkali metal in the superconducting layer 30 are measured by ICP (Inductively Coupled Plasma) analysis, that is, a method of dissolving the superconducting layer 30 in a solution and analyzing the ion concentration in the solution. In addition, the concentration of halogen (alkali metal) in the superconducting layer 30 is the mass ratio of halogen (alkali metal) to the total mass of all elements contained in the superconducting layer 30. That is, the total mass of all elements constituting the superconducting layer 30 is taken as 100%.

[0045] Sometimes 2 Cu 3 O 4 X 2 The superconducting layer 30 and the main surface 20b are precipitated at the interface between the superconducting layer 30 and the main surface 20b, in the superconducting layer 30, and on the main surface 30b. X is a halogen. Ba on the main surface 30b 2 Cu 3 O 4 X 2 The precipitation amount can be greater than that of Ba in the superconducting layer 30. 2 Cu 3 O 4 X 2 The amount of precipitation is large.

[0046] (Method for Manufacturing Superconducting Wire 100)

[0047] Below, refer to Figure 2 to Figure 7 A method for manufacturing superconducting wire 100 will be described.

[0048] like Figure 2 As shown, the method for manufacturing a superconducting wire 100 includes a preparation step S1, an intermediate layer forming step S2, a solution coating step S3, a first sintering step S4, and a second sintering step S5. The intermediate layer forming step S2 is performed after the preparation step S1. The solution coating step S3 is performed after the intermediate layer forming step S2. The first sintering step S4 is performed after the solution coating step S3. The second sintering step S5 is performed after the first sintering step S4.

[0049] like Figure 3 As shown, in the preparation step S1, the base material 10 is prepared. The intermediate layer 20 is not disposed on the base material 10 prepared in the preparation step S1.

[0050] like Figure 4 As shown, in the intermediate layer forming step S2, the intermediate layer 20 is formed on the substrate 10. The intermediate layer 20 is formed by sequentially forming each layer constituting the intermediate layer 20 by, for example, magnetron sputtering.

[0051] The superconducting layer 30 is formed by performing the solution coating step S3 , the first sintering step S4 , and the second sintering step S5 , that is, by the MOD (Metal Organic Decomposition) method. Figure 5 2 is a cross-sectional view illustrating the solution coating step S3. Figure 5 As shown, in the solution coating step S3, a coating film 31 is formed on the intermediate layer 20. The coating film 31 is formed by coating a solution on the intermediate layer 20 and drying the coated solution.

[0052] The solution contains a solvent and the constituent elements of the superconducting layer 30 mixed in the solvent. The solution contains halogen and alkali metal. More specifically, the solution has alcohol as a solvent, hydrochloric acid as a halogen source, sodium as an alkali metal, and rare earth elements, barium and copper as constituent elements of the superconducting layer 30. The concentration of the alkali metal in the solution may be 1 mass ppb or more. In addition, as an example of containing halogen and alkali metal in the solution, a solution in which halogen and alkali metal are added can be cited.

[0053] like Figure 6 As shown, in the first firing step S4, the coating film 31 is heated to form a pre-fired film 32. The pre-fired film 32 is composed of a precursor of the superconducting layer 30. The precursor of the superconducting layer 30 may be subjected to a drying process for removing the organic solvent and a drying process for forming REBa. 2 Cu 3 O x The heating in the first sintering step S4 is performed in an oxygen-containing atmosphere.

[0054] like Figure 7 As shown, in the second firing step S5, the pre-fired film 32 is heated to form the superconducting layer 30. The heating in the second firing step S5 is performed in an oxygen-containing atmosphere at a temperature higher than that in the first firing step S4.

[0055] During the heating in the second sintering step S5, REBa 2 Cu 3 O x The crystal is epitaxially grown and oriented in such a way that its c-axis is along the normal direction of the main surface 20b. When heating in the second sintering step S5 is performed, REBa is not easily generated. 2 Cu 3 Ox The epitaxial growth site of Ba 2 Cu 3 O 4 X 2 In this part, Ba 2 Cu 3 O 4 X 2 REBa is likely to occur around 2 Cu 3 O x Therefore, by making the solution contain halogen to promote REBa 2 Cu 3 O x orientation of the crystals.

[0056] By repeating the solution coating step S3, the first sintering step S4, and the second sintering step S5 in sequence, the film thickness of the superconducting layer 30 increases and becomes Figure 1 In addition, as the solution coating step S3, the first firing step S4, and the second firing step S5 are sequentially repeated, the halogen is concentrated on the main surface 30b of the superconducting layer 30 and its vicinity. Therefore, when the superconducting layer 30 is formed by the MOD method using a solution containing halogen, the Ba on the main surface 30b is 2 Cu 3 O 4 X 2 The precipitation amount is greater than that of Ba in the superconducting layer 30. 2 Cu 3 O 4 X 2 The amount of precipitation is large.

[0057] <Modification>

[0058] In the above example, a solution containing an alkali metal is used, but the alkali metal may be contained in the atmosphere when the second firing step S5 is performed instead of the solution. At this time, the partial pressure of the alkali metal in the atmosphere may be above 1000 Pa. The gas constituting the atmosphere when the second firing step S5 is performed may contain, for example, oxygen, an inert gas and an alkali metal. The inert gas is, for example, argon or nitrogen. The pressure of the atmosphere is, for example, atmospheric pressure (101.3 kPa). In addition, the alkali metal may also be contained in the pre-fired film 32. In addition, as an example of a case where the above-mentioned atmosphere or the pre-fired film 32 contains an alkali metal, an alkali metal may be added to the above-mentioned atmosphere or the pre-fired film 32.

[0059] As described above, the solution used in the solution coating step S3 contains an alkali metal, and therefore, the pre-sintered film 32 also contains an alkali metal. During the heating in the second sintering step S5, the alkali metal in the pre-sintered film 32 is vaporized. The vaporized alkali metal reacts with the chlorine in the superconducting layer 30 and is discharged to the outside. Therefore, in the superconducting wire 100, the concentration of halogen in the superconducting layer 30 is reduced to less than 2000 mass ppm compared to the case where the alkali metal is not contained in the solution. The concentration of halogen in the superconducting layer 30 can be reduced to, for example, 1800 mass ppm or less, and can also be reduced to 1500 mass ppm or less.

[0060] In addition, in superconducting wire 100, the concentration of halogen in superconducting layer 30 is reduced, and as a result, the REBa constituting superconducting layer 30 can be suppressed. 2 Cu 3 O x The composition balance is destroyed and the volume of the superconducting layer 30 is reduced.

[0061] In the superconducting wire 100, the solution used in the solution coating step S3 contains an alkali metal, and as a result, the alkali metal may remain in the superconducting layer 30. However, even if the alkali metal remains in the superconducting layer 30, it is unlikely to adversely affect the superconducting characteristics of the superconducting layer 30. The concentration of halogen in the superconducting layer 30 is reduced not only when the alkali metal is contained in the solution used in the solution coating step S3, but also when the alkali metal is contained in the atmosphere of the preliminary calcination film 32 and the second calcination step S5.

[0062] The embodiments disclosed this time should be considered as illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0063] Description of Reference Numerals

[0064] 10: substrate; 10a, 10b: main surface; 20: intermediate layer; 20a, 20b: main surface; 30: superconducting layer; 30a, 30b: main surface; 31: coating film; 32: pre-fired film; 100: superconducting wire; S1: preparation step; S2: intermediate layer forming step; S3: solution coating step; S4: first firing step; S5: second firing step.

Claims

1. A superconducting wire having a x The superconducting layer The RE is a rare earth element, The superconducting layer comprises a halogen, The concentration of the halogen in the superconducting layer is less than 2000 mass ppm.

2. The superconducting wire according to claim 1, wherein The concentration of the halogen in the superconducting layer is 2 mass ppm or more.

3. The superconducting wire according to claim 1 or claim 2, wherein: The halogen is chlorine.

4. The superconducting wire according to any one of claims 1 to 3, wherein The superconducting layer comprises an alkali metal, The concentration of the alkali metal in the superconducting layer is 1 mass ppb or more.

5. The superconducting wire according to claim 4, wherein: The alkali metal is sodium.

6. The superconducting wire according to any one of claims 1 to 5, wherein The superconducting wire further comprises: Base material; as well as an intermediate layer, which is disposed on the substrate, The superconducting layer has a first main surface and a second main surface opposite to the first main surface, The superconducting layer is arranged on the intermediate layer in such a manner that the first main surface faces the intermediate layer. The amount of Ba2Cu3O4X2 precipitated on the second main surface is greater than the amount of Ba2Cu3O4X2 precipitated in the superconducting layer. The X is a halogen.

7. A method for manufacturing a superconducting wire, comprising forming a superconducting wire composed of REBa2Cu3O on an intermediate layer disposed on a substrate. x The process of forming the superconducting layer, The RE is a rare earth element, The formation of REBa2Cu3O x The process of forming the superconducting layer includes: A step of applying a solution containing constituent elements of the superconducting layer onto the intermediate layer; A step of heating the applied solution to form a precursor of the superconducting layer; and a step of forming the precursor into the superconducting layer by heating the precursor, The solution comprises a halogen, At least any one of the solution, the precursor, and an atmosphere when the precursor is heated contains an alkali metal.

8. The method for producing a superconducting wire according to claim 7, wherein: The concentration of the alkali metal in the solution is 1 mass ppb or more.

9. The method for producing a superconducting wire according to claim 7 or claim 8, wherein: The partial pressure of the alkali metal in the atmosphere is 1000 Pa or less.

10. The method for producing a superconducting wire according to any one of claims 7 to 9, wherein: The halogen is chlorine.

11. The method for producing a superconducting wire according to any one of claims 7 to 10, wherein: The alkali metal is sodium.

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