Oxide superconducting wire

Abstract

This invention provides an oxide superconducting wire comprising: a substrate having a main surface; a superconducting layer disposed above the substrate and composed of a rare-earth high-temperature superconductor; and a protective layer disposed on and in contact with the superconducting layer. The superconducting layer includes a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. The a-axis oriented particle ratio, representing the proportion of the a-axis oriented particles relative to the total number of crystal particles constituting the superconducting layer, is in the range of 4.1% to 11.9%.

Description

Technical Field

[0001] This invention relates to an oxide superconducting wire.

[0002] This application claims priority based on Japanese Patent Application No. 2020-160613, filed in Japan on September 25, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] Patent document 1 discloses an oxide superconducting wire having a structure in which an intermediate layer, a superconducting layer and a protective layer are sequentially stacked on a substrate.

[0004] To manufacture superconducting wires that can be thousands of meters long, multiple short superconducting wires are typically joined together by welding.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-110125 Summary of the Invention

[0008] The technical problem to be solved by the present invention

[0009] However, when joining oxide superconducting wires by welding, problems arise such as increased connection resistance and Joule heating at the joint. Specifically, the interlayer resistance between the superconducting layer and the protective layer dominates the connection resistance caused by welding; therefore, reducing this interlayer resistance is crucial to minimizing Joule heating. Furthermore, a higher connection resistance makes it difficult for bypass current to flow from the superconducting layer to the protective layer during quenching.

[0010] The present invention was made in view of the following circumstances, and its object is to provide an oxide superconducting wire with reduced interlayer resistance between the superconducting layer and the protective layer.

[0011] Technical means to solve technical problems

[0012] To address the aforementioned technical problems, one aspect of the present invention is an oxide superconducting wire comprising: a substrate having a main surface; a superconducting layer disposed above the substrate and composed of a rare-earth high-temperature superconductor; and a protective layer disposed on and in contact with the superconducting layer. The superconducting layer contains a-axis oriented particles, the a-axis of which is oriented in a direction perpendicular to the main surface of the substrate. The a-axis oriented particle ratio, representing the proportion of the a-axis oriented particles relative to the total number of crystal particles constituting the superconducting layer, is in the range of 4.1% to 11.9%.

[0013] The phrase "a superconducting layer disposed above the substrate" refers not only to a superconducting layer disposed on the substrate, but also to a structure in which an intermediate layer or other film is disposed between the substrate and the superconducting layer, and a superconducting substrate is disposed above the substrate.

[0014] In the crystal structure of a superconducting layer where the crystal is oriented along the a-axis, b-axis, and c-axis, it is known that the c-axis of the crystal particles is mostly oriented in a direction perpendicular to the main plane of the substrate. In contrast, the inventors of this application discovered that a-axis oriented particles, where the a-axis is oriented perpendicular to the main plane of the substrate, affect the interlayer resistance between the superconducting layer and the protective layer. Further research revealed that by forming a superconducting layer with a-axis oriented particles comprising 4.1% to 11.9% of the total crystal particles, a reduction in interlayer resistance between the superconducting layer and the protective layer can be achieved, leading to the invention of this application.

[0015] According to one aspect of the present invention, it is possible to manufacture oxide superconducting wires with reduced interlayer resistance between the superconducting layer and the protective layer. By preparing multiple such oxide superconducting wires and welding overlapping oxide superconducting wires together, long superconducting wires with reduced connection resistance can be manufactured.

[0016] In one embodiment of the oxide superconducting wire of the present invention, the a-axis orientation particle ratio can be 8.2% or less.

[0017] This configuration not only reduces interlayer resistance but also ensures the critical current density along the length of the oxide superconducting wire.

[0018] To address the aforementioned technical problems, one embodiment of the present invention provides an oxide superconducting wire comprising: a substrate having a main surface; a first superconducting layer disposed above the substrate and composed of a rare-earth high-temperature superconductor; a second superconducting layer disposed on the first superconducting layer and composed of a rare-earth high-temperature superconductor; and a protective layer disposed on and in contact with the second superconducting layer. The second superconducting layer contains a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. The a-axis oriented particle ratio, representing the proportion of the a-axis oriented particles relative to the total number of crystal particles constituting the second superconducting layer, is in the range of 4.1% to 11.9%.

[0019] According to one aspect of the present invention, it is possible to manufacture oxide superconducting wires with reduced interlayer resistance between the second superconducting layer and the protective layer. By preparing multiple such oxide superconducting wires and welding overlapping oxide superconducting wires together, long superconducting wires with reduced connection resistance can be manufactured.

[0020] In one embodiment of the oxide superconducting wire of the present invention, the first superconducting layer contains first a-axis oriented particles, which are a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. The second superconducting layer contains second a-axis oriented particles, which are a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. A first ratio is defined as the a-axis oriented particle ratio, which represents the proportion of the first a-axis oriented particles relative to the total number of crystal particles constituting the first superconducting layer, and a second ratio is defined as the a-axis oriented particle ratio, which represents the proportion of the second a-axis oriented particles relative to the total number of crystal particles constituting the second superconducting layer. In this case, the first ratio may be less than the second ratio.

[0021] According to this configuration, the interlayer resistance between the superconducting layer and the protective layer can be reduced by the second superconducting layer, and the critical current density in the longitudinal direction of the oxide superconducting wire can be ensured by the first superconducting layer. That is, by equipping the oxide superconducting wire with two superconducting layers having different a-axis orientation particle rates, both the effects of reducing interlayer resistance and ensuring the critical current density in the longitudinal direction of the oxide superconducting wire can be achieved.

[0022] Invention Effects

[0023] According to the above-described scheme of the present invention, the interlayer resistance between the superconducting layer and the protective layer can be reduced. Attached Figure Description

[0024] Figure 1 An enlarged cross-sectional view of an oxide superconducting wire according to a first embodiment of the present invention is shown.

[0025] Figure 2 An enlarged cross-sectional view of an oxide superconducting wire according to a second embodiment of the present invention is shown.

[0026] Figure 3 The diagram illustrates a connection structure formed using an embodiment of the present invention, specifically an enlarged cross-sectional view showing a connection structure formed by welding two of a plurality of oxide superconducting wires together. Detailed Implementation

[0027] Hereinafter, the oxide superconducting wire of the present invention will be described in detail with reference to the accompanying drawings. For ease of understanding of the features of the present invention, important parts of the figures used in the description may be enlarged, and the dimensional ratios of the constituent elements may not be the same as in reality.

[0028] (First Implementation Plan)

[0029] First, refer to Figure 1The oxide superconducting wire of the first embodiment is described.

[0030] The oxide superconducting wire 1A of this embodiment includes: a substrate 10, an intermediate layer 11 disposed on the substrate 10, a superconducting layer 12 disposed on the intermediate layer 11, a protective layer 13 disposed on the superconducting layer 12, and a stabilizing layer 14 disposed on the protective layer 13. The oxide superconducting wire 1A may have an insulating covering layer that covers the substrate 10, the intermediate layer 11, the superconducting layer 12, the protective layer 13, and the stabilizing layer 14.

[0031] The height of the oxide superconducting wire 1A, i.e., the height from the lower surface of the substrate 10 to the upper surface of the protective layer 13. Figure 1 (The length in the vertical direction) is, for example, 80 μm.

[0032] The width of oxide superconducting wire 1A, i.e., the length from the left end to the right end of oxide superconducting wire 1A ( Figure 1 (The length in the left and right directions) is, for example, 12mm.

[0033] (Substrate 10)

[0034] The substrate 10 is a strip-shaped metal substrate. Specific examples of metals constituting the metal substrate include nickel alloys represented by Hastelloy (registered trademark), stainless steel, and oriented Ni-W alloys in which agglomerated structures are introduced into nickel alloys.

[0035] (Middle layer 11)

[0036] The intermediate layer 11 can be a multilayer structure, for example, it can have a diffusion-preventing layer, a bed layer, an alignment layer, a capping layer, etc., sequentially arranged from the substrate 10 toward the superconducting layer 12. In the structure in which the intermediate layer 11 has the above-mentioned multiple layers, the number of each layer is not limited to one. Some of the multiple layers constituting the intermediate layer 11 may also be omitted. In addition, a structure formed by repeatedly stacking two or more layers of the same type may also be used. The intermediate layer 11 can be a metal oxide. By forming the superconducting layer 12 on the intermediate layer 11 with excellent orientation, it is easy to obtain the superconducting layer 12 with excellent orientation.

[0037] (Superconducting layer 12)

[0038] The superconducting layer 12 has the function of allowing current to flow in the superconducting state.

[0039] The superconducting layer 12 is made of rare-earth high-temperature superconductors and is arranged in contact with the protective layer 13.

[0040] Specifically, as a material for the superconducting layer 12, oxide superconductors of commonly known compositions can be widely used, such as copper oxide superconductors, including Y-series superconductors and Bi-series superconductors.

[0041] Examples of components of Y-type superconductors include REBa₂Cu₃O. 7-x (RE represents rare earth elements such as Y, La, Nd, Sm, Er, and Gd, and x represents oxygen vacancies.)

[0042] As specific components of Y-series superconductors, Y123(YBa2Cu3O) can be listed. 7-x ), Gd123(GdBa2Cu3O) 7-x ).

[0043] Examples of Bi-based superconductors include Bi₂Sr₂Ca. n-1 Cu n O 4+2n+δ (n represents the number of CuO2 layers, and δ represents excess oxygen.) Although the masterbatch of this oxide superconductor is an insulator, oxygen is obtained by oxygen annealing, thus making it an oxide superconductor with a complete crystal structure and exhibiting superconducting properties.

[0044] Furthermore, the superconducting layer 12 contains a-axis oriented particles, which are crystal particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate 10. In the a-axis oriented particles, the Cu-O surface, where current flows easily in the superconducting state, exists perpendicular to the main surface of the substrate. The superconducting layer 12 containing a-axis oriented particles exhibits excellent quantum coupling at the grain boundaries between the a-axis oriented particles, and the superconducting properties at the grain boundaries are almost not degraded. Therefore, in the superconducting layer 12, current easily flows along the a-axis direction. The proportion of a-axis oriented particles contained in the superconducting layer 12 (a-axis oriented particle ratio Xa) relative to the total number (100%) of crystal particles constituting the superconducting layer 12 is in the range of 4.1% to 11.9%. Furthermore, within this range, the a-axis oriented particle ratio Xa is more preferably 8.2% or less.

[0045] When forming the superconducting layer 12, the a-axis orientation particle rate Xa can be controlled to the desired value within the above range by adjusting the film formation temperature, film formation rate (film formation speed), and other conditions.

[0046] (Protective layer 13)

[0047] The protective layer 13 serves as a current path, acting as a bypass path in which an overcurrent caused by a fault flows when current is supplied to the oxide superconducting wire 1A. The protective layer 13 is preferably formed of Ag or a material containing at least Ag. Furthermore, the material forming the protective layer 13 can be a mixture or alloy containing noble metals such as Au and Pt, or a combination of these materials.

[0048] (Stable layer 14)

[0049] The material for the stabilizing layer 14 can be selected from copper, Cu-Zn alloy (brass), Cu-Ni alloy and other copper alloys, aluminum, aluminum alloys, stainless steel and other materials.

[0050] The stabilizing layer 14 may be composed of multiple layers. Furthermore, the stabilizing layer 14 may be formed by metal plating. The stabilizing layer 14 may have an overall structure in which a plating covers a laminate comprising the substrate 10, the protective layer 13, and the layers located between the substrate 10 and the protective layer 13.

[0051] Next, the function and effect of the oxide superconducting wire 1A constructed as described above will be explained.

[0052] The superconducting layer 12, which is in contact with the protective layer 13, contains a-axis oriented particles with the a-axis oriented in a direction perpendicular to the main surface of the substrate 10. Thus, the Cu-O surface, serving as the current path for the superconducting conductor, exists perpendicular to the main surface of the substrate 10. By oriented the a-axis in a direction perpendicular to the main surface of the substrate 10, low resistance is obtained in this direction, facilitating current flow. As described later, in particular, by setting the a-axis oriented particle ratio Xa in the range of 4.1% to 11.9%, the interlayer resistance between the superconducting layer 12 and the protective layer 13 can be reduced. Furthermore, by setting the a-axis oriented particle ratio Xa to 8.2% or less, not only is the interlayer resistance reduced, but the decrease in the critical current density along the length of the oxide superconducting wire 1A can also be suppressed. In the following description, the critical current density along the length of the oxide superconducting wire will be referred to simply as the critical current density.

[0053] On the other hand, in conventional oxide superconducting wires, the superconducting layer is typically formed such that the Cu-O plane exists in a direction parallel to the main surface of the substrate. In this case, since the c-axis of the crystal grains is oriented in a direction perpendicular to the main surface of the substrate, it is difficult for current to flow in a direction perpendicular to the main surface of the substrate.

[0054] In this embodiment, by optimizing the proportion of a-axis oriented particles (a-axis oriented particle ratio Xa) that are oriented in a direction perpendicular to the main surface of the substrate 10, the amount of current flowing between the superconducting layer 12 and the protective layer 13 is increased, thereby reducing the interlayer resistance.

[0055] (Second Implementation Plan)

[0056] Next, refer to Figure 2 The oxide superconducting wire of the second implementation scheme is described.

[0057] The oxide superconducting wire 1B of this embodiment differs from the oxide superconducting wire 1A of the first embodiment in that the superconducting layer consists of two layers (a first superconducting layer and a second superconducting layer).

[0058] exist Figure 2 In this document, the same symbols are used for components that are identical to those in the first embodiment, and their descriptions are omitted or simplified.

[0059] The oxide superconducting wire 1B of this embodiment comprises: a substrate 10, an intermediate layer 11 disposed on the substrate 10, a first superconducting layer 12A disposed on the intermediate layer 11, a second superconducting layer 12B disposed on the first superconducting layer 12A, a protective layer 13 disposed on the second superconducting layer 12B, and a stabilizing layer 14 disposed on the protective layer 13. The oxide superconducting wire 1B may have an insulating covering layer covering the substrate 10, the intermediate layer 11, the first superconducting layer 12A, the second superconducting layer 12B, the protective layer 13, and the stabilizing layer 14.

[0060] The first superconducting layer 12A and the second superconducting layer 12B are each composed of rare-earth high-temperature superconductors. The first superconducting layer 12A is formed on the intermediate layer 11 and is not in contact with the protective layer 13. The second superconducting layer 12B is formed on the first superconducting layer 12A and is in contact with the protective layer 13.

[0061] Similar to the superconducting layer 12 in the first embodiment described above, the proportion of the a-axis oriented particles (second a-axis oriented particles) of the second superconducting layer 12B relative to the total number of crystal particles constituting the second superconducting layer 12B (the a-axis oriented particle ratio of the second superconducting layer 12B, the second ratio) is in the range of 4.1% to 11.9%.

[0062] On the other hand, the proportion of the a-axis oriented particles (first a-axis oriented particles) of the first superconducting layer 12A relative to the total number of crystal particles constituting the first superconducting layer 12A (the a-axis oriented particle ratio Xa1 of the first superconducting layer 12A, the first ratio) is lower than the a-axis oriented particle ratio Xa2 of the second superconducting layer 12B.

[0063] For example, if the a-axis orientation particle ratio Xa2 of the second superconducting layer 12B is 4.1%, then the a-axis orientation particle ratio Xa1 of the first superconducting layer 12A is preferably less than 4.1%.

[0064] Furthermore, if the a-axis orientation particle ratio Xa2 of the second superconducting layer 12B is 11.9%, then the a-axis orientation particle ratio Xa1 of the first superconducting layer 12A can be less than 11.9%. A higher critical current density is achieved by setting the a-axis orientation particle ratio Xa to below 8.2%, therefore, the a-axis orientation particle ratio Xa1 of the first superconducting layer 12A is preferably below 8.2%.

[0065] Next, the function and effect of the oxide superconducting wire 1B constructed as described above will be explained.

[0066] The second superconducting layer 12B, which is in contact with the protective layer 13, contains a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. Because of these a-axis oriented particles, the Cu-O surface, serving as a superconducting current path, exists perpendicular to the main surface of the substrate. By oriented the a-axis in a direction perpendicular to the main surface of the substrate 10, low resistance is obtained in this direction, facilitating current flow. As described later, by setting the a-axis oriented particle ratio Xa2 of the second superconducting layer 12B in the range of 4.1% to 11.9%, the interlayer resistance between the second superconducting layer 12B and the protective layer 13 can be reduced. Furthermore, since the value of the a-axis oriented particle ratio Xa1 of the first superconducting layer 12A is smaller than the value of the a-axis oriented particle ratio Xa2 of the second superconducting layer 12B, the proportion of crystal particles oriented along the length direction of the oxide superconducting wire 1B, either a-axis or b-axis, can be ensured. Therefore, a higher critical current density of the oxide superconducting wire 1B can be obtained. In particular, by setting the a-axis orientation particle ratio Xa1 of the first superconducting layer 12A to below 8.2%, a higher critical current density can be obtained.

[0067] Therefore, by increasing the amount of current flowing between the second superconducting layer 12B and the protective layer 13, the interlayer resistance can be reduced, and the critical current density of the first superconducting layer 12A can be ensured. That is, by having the oxide superconducting wire 1B have two superconducting layers with different a-axis orientation particle ratios Xa1 and Xa2, the effects of reducing interlayer resistance and ensuring critical current density can be achieved.

[0068] In the second embodiment described above, although the number of layers constituting the superconducting layer is two, as long as the a-axis orientation particle rate Xa of the superconducting layer in contact with the protective layer is in the range of 4.1% to 11.9%, the superconducting layer can also be composed of three or more layers.

[0069] (Connection structure)

[0070] Next, refer to Figure 3 The connection structure formed using the oxide superconducting wire of the present invention described above will be explained.

[0071] The connection structure formed using the oxide superconducting wires of the embodiments of the present invention has a structure formed by welding together a plurality of oxide superconducting wires 1A of the first embodiment. Specifically, Figure 3 The connection formed by welding two oxide superconducting wires is shown.

[0072] like Figure 3 As shown, an oxide superconducting wire ( Figure 3 The surface of the stabilizing layer 14 of the protective layer 13 of the oxide superconducting wire (located above) and another oxide superconducting wire ( Figure 3 The surfaces of the stabilizing layer 14 of the protective layer 13 (located below the oxide superconducting wire) are opposite to each other. "One oxide superconducting wire" can be referred to as the first oxide superconducting wire. "The other oxide superconducting wire" can be referred to as the second oxide superconducting wire. "One oxide superconducting wire" and "the other oxide superconducting wire" can be referred to as "overlapping oxide superconducting wires." Furthermore, overlapping oxide superconducting wires means that the oxide superconducting wires coincide in the thickness direction of the oxide superconducting wires.

[0073] In this state, the stabilizing layer 14 at the end of one oxide superconducting wire and the stabilizing layer 14 at the end of another oxide superconducting wire are electrically connected via solder 15.

[0074] in addition, Figure 3 Although not shown, the ends of the two oxide superconducting wires are connected to other oxide superconducting wires via solder. In this connection structure, a method is employed... Figure 3 The electrical connection structure shown uses solder 15. That is, a long oxide superconducting wire can be obtained by welding multiple oxide superconducting wires along the extension direction of the oxide superconducting wire.

[0075] Based on this structure, it is possible to manufacture long oxide superconducting wires with reduced connection resistance.

[0076] Alternatively, multiple oxide superconducting wires 1B of the second embodiment can be prepared to replace the multiple oxide superconducting wires 1A of the first embodiment, such as... Figure 3 As shown, overlapping oxide superconducting wires 1B are welded together. This allows for the fabrication of long superconducting wires that reduce connection resistance while ensuring critical current density.

[0077] The preferred embodiments of the present invention have been described above. While described above, it should be understood that this is merely illustrative and should not be considered a limiting description. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Therefore, the present invention is defined by the claims and should not be considered as limited by the above description.

[0078] In the above embodiments, a structure in which an intermediate layer 11 is disposed between the substrate 10 and the superconducting layer 12 (first embodiment) and a structure in which an intermediate layer 11 is disposed between the substrate 10 and the first superconducting layer 12A (second embodiment) are described.

[0079] In this invention, it is sufficient to provide a superconducting layer on top of the substrate. The superconducting layer can be provided on the substrate or it can be directly in contact with the substrate.

[0080] Example

[0081] Next, the present invention will be specifically described with reference to the embodiments.

[0082] Table 1 shows the evaluation results of critical current density ratio, interlayer resistance ratio (R ratio), and interlayer resistance R ratio in Experimental Examples 1 to 9 with different a-axis orientation particle ratios Xa (%), which is the proportion of a-axis orientation particles relative to the total number of crystal particles constituting the superconducting layer.

[0083] [Table 1]

[0084]

[0085] The methods for determining and calculating the a-axis orientation particle rate Xa, critical current density ratio, and interlayer resistivity ratio (R ratio), as well as the evaluation criteria for the interlayer resistivity R ratio, are described below.

[0086] (a-axis orientation particle rate Xa)

[0087] The a-axis orientation particle rate Xa was determined for the sample before oxygen annealing (as deposition).

[0088] The a-axis orientation particle rate Xa was determined using the θ-2θ method of XRD. When the count value of the (006) peak is set as x and the count value of the (200) peak is set as y, the a-axis orientation particle rate Xa can be calculated using the relationship "(a-axis orientation particle rate Xa(%))=(100×y) / (x+y)".

[0089] (Critical current density ratio (Jc ratio))

[0090] In the determination and calculation of the critical current density Jc (77K, in a self-magnetic field), a sample after oxygen annealing was first prepared, and the measured value was obtained using the four-terminal method. The critical current density Jc was obtained by dividing the measured value by the thickness of the superconducting layer.

[0091] In Table 1, “critical current density ratio (Jc ratio)” represents the ratio relative to the critical current density Jc of Experimental Example 1, that is, the ratio when the critical current density Jc of Experimental Example 1 is set to 1.

[0092] (Interlayer resistivity ratio (R ratio))

[0093] The interlayer resistance R was measured under the bridging condition on both the front and back sides of the wires without replacement. The connection length was 2 cm. In the bridging process, Sn-Pb eutectic solder was applied between the connection surfaces of the two wires, the connection surfaces were aligned, and a heater was pressed onto the overlapping part of the connection surfaces for measurement.

[0094] In Table 1, “interlayer resistance ratio (R ratio)” represents the ratio relative to the interlayer resistance of Experimental Example 1, that is, the ratio when the interlayer resistance of Experimental Example 1 is set to 1.

[0095] (Evaluation of interlayer resistivity R ratio)

[0096] In Table 1, a result of "Good" indicates an interlayer resistivity R-ratio of 0.7 or less, and the evaluation result is good. A result of "Best" indicates an interlayer resistivity R-ratio of 0.5 or less, and the evaluation result is excellent. On the other hand, a result of "Unacceptable" indicates an interlayer resistivity R-ratio of greater than 0.7, and the evaluation result is poor.

[0097] The following points can be observed from the implementation results shown in Table 1.

[0098] (1) When the a-axis orientation particle ratio Xa is in the range of 4.1% to 11.9%, the evaluation result of the interlayer resistance R ratio is good or optimal. Therefore, it can be seen that by setting the a-axis orientation particle ratio Xa of the superconducting layer within this range, the interlayer resistance can be reduced.

[0099] (2) On the other hand, when the a-axis orientation particle ratio Xa is less than 4.1% (3.3%, 2.9%) and greater than 11.9% (27.1%, 41.7%), the interlayer resistivity increases, and the evaluation result of the interlayer resistivity R ratio is unacceptable. It can be seen that it is impossible to reduce the interlayer resistivity under these conditions.

[0100] In addition, it is believed that the interlayer resistivity increases when the a-axis orientation particle ratio Xa is greater than 11.9%. This is because although a current path in the longitudinal direction (the direction perpendicular to the main surface of the substrate) can be obtained by increasing the a-axis orientation particle ratio Xa, the crystal arrangement of the superconducting layer becomes disordered due to the excessive number of a-axis orientation particles, generating other particles that hinder the current, resulting in uneven Cu-O surfaces and increased resistance.

[0101] (3) When the a-axis orientation particle ratio Xa is in the range of 4.1% to 11.9%, as long as the a-axis orientation particle ratio Xa is below 8.2%, the critical current density ratio is above 0.85. It can be seen that the two effects of reducing interlayer resistance and ensuring critical current density can be achieved.

[0102] (4) When the a-axis orientation particle ratio Xa is 4.1% or less, the critical current density ratio is 0.95 or more. Therefore, it can be seen that in a structure having a first superconducting layer that is not in contact with the protective layer and a second superconducting layer that is in contact with the protective layer, by setting the a-axis orientation particle ratio Xa2 of the second superconducting layer in the range of 4.1% to 11.9% and setting the a-axis orientation particle ratio Xa1 of the first superconducting layer to 4.1% or less, the effects of reducing interlayer resistance and ensuring critical current density can be achieved.

[0103] Furthermore, it is known that in a structure having a first superconducting layer and a second superconducting layer, it is possible to set the a-axis orientation particle ratio Xa2 of the second superconducting layer in the range of 4.1% to 11.9% and set the a-axis orientation particle ratio Xa1 of the first superconducting layer to 11.9% or less. However, in order to obtain a higher critical current density, it is preferable to set the a-axis orientation particle ratio Xa1 of the first superconducting layer to 8.2% or less.

[0104] Explanation of reference numerals in the attached figures

[0105] 1A, 1B: Oxide superconducting wire; 10: Substrate; 11: Intermediate layer; 12: Superconducting layer; 12A: First superconducting layer; 12B: Second superconducting layer; 13: Protective layer; 14: Stabilizing layer; 15: Solder.

Claims

1. An oxide superconducting wire, comprising: A substrate with a main surface; A first superconducting layer, which is disposed above the substrate and is composed of rare-earth high-temperature superconductors, is formed. A second superconducting layer, disposed on the first superconducting layer and composed of rare-earth high-temperature superconductors, and A protective layer disposed on and in contact with the second superconducting layer. in, The second superconducting layer contains a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. The a-axis orientation particle ratio, representing the proportion of the a-axis oriented particles relative to the total number of crystal particles constituting the second superconducting layer, is in the range of 6.8% to 11.9%. The first superconducting layer contains first a-axis oriented particles, which are a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. The second superconducting layer contains second a-axis oriented particles, which are a-axis oriented particles whose a-axis is oriented in a direction perpendicular to the main surface of the substrate. The a-axis orientation particle ratio, which represents the proportion of the first a-axis oriented particles relative to the total number of crystal particles constituting the first superconducting layer, is defined as the first ratio. And when the a-axis orientation particle ratio, which represents the proportion of the second a-axis orientation particles relative to the total number of crystal particles constituting the second superconducting layer, is defined as the second ratio. The first ratio is less than the second ratio.

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