Bonded body and method for manufacturing the bonded body

Abstract

This joined body is provided with a first superconducting layer, a barrier layer arranged on the first superconducting layer, and a second superconducting layer arranged on the barrier layer. The first superconducting layer, the barrier layer, and the second superconducting layer are formed from REBCO. Leak current from one of the first superconducting layer and the second superconducting layer to the other of the first superconducting layer and the second superconducting layer is blocked by the barrier layer.

Description

Technical Field

[0001] The present disclosure relates to a bonded body and a method for manufacturing the bonded body. This application claims priority based on Japanese Patent Application No. 2021-067673, filed on April 13, 2021. All the descriptions described in the Japanese patent application are incorporated herein by reference.

Background Art

[0002] For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 10-65226) describes a bonded body. The bonded body described in Patent Document 1 has a first superconducting layer, a non-superconducting layer, and a second superconducting layer. The non-superconducting layer is disposed on the first superconducting layer. The second superconducting layer is disposed on the non-superconducting layer.

[0003] The first superconducting layer and the second superconducting layer are formed of YBa2Cu3O x The non-superconducting layer is formed of PrBa2Cu3O x Thereby, the first superconducting layer, the second superconducting layer, and the non-superconducting layer constitute a Josephson junction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The bonded body of the present disclosure includes a first superconducting layer, a barrier layer disposed on the first superconducting layer, and a second superconducting layer disposed on the barrier layer. The first superconducting layer, the barrier layer, and the second superconducting layer are formed of REBCO. The leakage current from one of the first superconducting layer and the second superconducting layer to the other of the first superconducting layer and the second superconducting layer is blocked by the barrier layer.

[0006] The method for manufacturing the bonded body of the present disclosure includes a step of forming a first superconducting layer on a first substrate, a step of forming a second superconducting layer on a second substrate, a step of forming a microcrystalline layer on either the first superconducting layer or the second superconducting layer, and a step of heating the first substrate and the second substrate while holding the first substrate and the second substrate in a state where the microcrystalline layer is sandwiched between the first superconducting layer and the second superconducting layer. The first superconducting layer and the second superconducting layer are formed of REBCO. The microcrystalline layer is formed of a polycrystal of REBCO.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

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Embodiments for Carrying Out the Invention

[0008] [Problems to be Solved by the Present Disclosure] In the manufacturing process of the bonded body described in Patent Document 1, a non-superconducting layer is epitaxially grown on the first superconducting layer. In the manufacturing method of the bonded body described in Patent Document 1, thereafter, a second superconducting layer is epitaxially grown on the non-superconducting layer. Therefore, when the second superconducting layer is epitaxially grown, yttrium in the first superconducting layer and yttrium in the second superconducting layer diffuse into the non-superconducting layer.

[0009] Therefore, in the junction described in Patent Document 1, the yttrium diffused into the non-superconducting layer causes the non-superconducting layer to become a superconductor at least partially, forming a path through which a superconducting current flows in the non-superconducting layer, resulting in a leakage current flowing between the first superconducting layer and the second superconducting layer. That is, in the junction described in Patent Document 1, pinholes are formed in the non-superconducting layer, causing a leakage current to flow between the first superconducting layer and the second superconducting layer. When a leakage current flows between the first superconducting layer and the second superconducting layer, the Josephson effect does not occur.

[0010] The present disclosure has been made in view of the problems of the prior art as described above. More specifically, the present disclosure provides a junction capable of blocking leakage current between a first superconducting layer and a second superconducting layer, and a method for manufacturing the junction. [Effects of the Present Disclosure] According to the junction and the method for manufacturing the junction of the present disclosure, it is possible to block leakage current between the first superconducting layer and the second superconducting layer.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] (1) A junction according to an embodiment includes a first superconducting layer, a barrier layer disposed on the first superconducting layer, and a second superconducting layer disposed on the barrier layer. The first superconducting layer, the barrier layer, and the second superconducting layer are formed of REBCO. Leakage current from one of the first superconducting layer and the second superconducting layer to the other of the first superconducting layer and the second superconducting layer is blocked by the barrier layer.

[0013] According to the junction of (1) above, it is possible to block leakage current between the first superconducting layer and the second superconducting layer.

[0014] (2) In the junction body of the above (1), the rare earth elements in the REBCO constituting the first superconducting layer and the second superconducting layer may be selected such that the first superconducting layer and the second superconducting layer exhibit superconducting characteristics. The rare earth elements in the REBCO constituting the barrier layer may be selected such that the barrier layer does not exhibit superconducting characteristics.

[0015] According to the junction body of the above (2), by changing the component of the rare earth element in the REBCO constituting the barrier layer, it is possible to block the leakage current between the first superconducting layer and the second superconducting layer.

[0016] (3) In the junction body of the above (2), the rare earth elements in the REBCO constituting the first superconducting layer and the second superconducting layer may be at least one element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, lutetium, and ytterbium. The rare earth element in the REBCO constituting the barrier layer may be praseodymium. Two According to the junction body of the above (3), by changing the component of the rare earth element in the REBCO constituting the barrier layer, it is possible to block the leakage current between the first superconducting layer and the second superconducting layer.

[0017] According to the junction body of the above (3), by changing the component of the rare earth element in the REBCO constituting the barrier layer, it is possible to block the leakage current between the first superconducting layer and the second superconducting layer.

[0018] (4) In the junction body of the above (2) or the above (3), the barrier layer may grow epitaxially from the first superconducting layer and the second superconducting layer.

[0019] According to the junction body of the above (4), by changing the component of the rare earth element in the REBCO constituting the barrier layer, it is possible to block the leakage current between the first superconducting layer and the second superconducting layer.

[0020] (5) In the bonded body of the above (1), the barrier layer may have a first layer disposed on the first superconducting layer and a second layer disposed on the first layer. The c-axis direction of the REBCO constituting the first layer may be along the c-axis direction of the REBCO constituting the second layer. The a-axis direction of the REBCO constituting the first layer may be different from the a-axis direction of the REBCO constituting the second layer.

[0021] According to the bonded body of the above (5), by making the a-axis direction of the REBCO constituting the first layer different from the a-axis direction of the REBCO constituting the second layer, it is possible to block the leakage current between the first superconducting layer and the second superconducting layer.

[0022] (6) In the bonded body of the above (5), the first layer may grow epitaxially from the first superconducting layer, and the second layer may grow epitaxially from the second superconducting layer. The c-axis direction of the REBCO constituting the first superconducting layer may be along the c-axis direction of the REBCO constituting the second superconducting layer. The a-axis direction of the REBCO constituting the first superconducting layer may be different from the a-axis direction of the REBCO constituting the second superconducting layer.

[0023] According to the bonded body of the above (6), by making the a-axis direction of the REBCO constituting the first superconducting layer different from the a-axis direction of the REBCO constituting the second superconducting layer, the a-axis direction of the REBCO constituting the first layer can be made different from the a-axis direction of the REBCO constituting the second layer. Therefore, it is possible to block the leakage current between the first superconducting layer and the second superconducting layer.

[0024] (7) In the bonded body of the above (5) or the above (6), the rare earth element in the REBCO constituting the first superconducting layer, the second superconducting layer, and the barrier layer may be at least one element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, lutetium, and ytterbium. Two It may be at least one or more elements selected from the group consisting of um, dysprosium, holmium, erbium, thulium, lutetium, and ytterbium.

[0025] According to the junction body of (7) above, it is possible to block the leakage current between the first superconducting layer and the second superconducting layer without making the rare earth element in the REBCO constituting the first superconducting layer and the second superconducting layer different from the rare earth element in the REBCO constituting the barrier layer.

[0026] (8) The junction body of (1) to (7) above may further include a substrate. The first superconducting layer may be disposed on the substrate. The substrate may be formed of at least one or more oxides selected from cerium oxide, yttria-stabilized zirconia, lanthanum manganate, sapphire, or strontium titanate.

[0027] According to the junction body of (8) above, by increasing the oxygen permeability of the substrate, it becomes easier to supply oxygen to the first superconducting layer through the substrate.

[0028] (9) The junction body of (1) to (7) above may further include a metal substrate and an intermediate layer disposed on the metal substrate. The first superconducting layer may be disposed on the intermediate layer. The intermediate layer may be formed of at least one or more oxides selected from cerium oxide, yttria-stabilized zirconia, lanthanum manganate, sapphire, or strontium titanate.

[0029] According to the junction body of (9) above, by increasing the oxygen permeability of the intermediate layer, it becomes easier to supply oxygen to the first superconducting layer through the intermediate layer.

[0030] (10) The junction body of (1) to (7) above may further include a substrate. The first superconducting layer may be disposed on the substrate. The c-axis direction of the REBCO constituting the first superconducting layer may be along either the direction of the main surface on the first superconducting layer side of the substrate or the normal direction of the main surface.

[0031] According to the junction body of (10) above, either an a-axis oriented film or a c-axis oriented film can be used as the substrate on which the first superconducting layer is formed.

[0032] (11) The method for manufacturing a joined body according to one embodiment includes a step of forming a first superconducting layer on a first substrate, a step of forming a second superconducting layer on a second substrate, a step of forming a microcrystalline layer on either the first superconducting layer or the second superconducting layer, and a step of heating the first substrate and the second substrate while holding the first substrate and the second substrate such that the microcrystalline layer is sandwiched between the first superconducting layer and the second superconducting layer. The first superconducting layer and the second superconducting layer are formed of REBCO. The microcrystalline layer is formed of polycrystals of REBCO.

[0033] According to the method for manufacturing a joined body in (11) above, it is possible to block leakage current between the first superconducting layer and the second superconducting layer.

[0034] (12) In the method for manufacturing a joined body in the above ( 11 ), in the step of heating the first substrate and the second substrate, at least a part of the microcrystalline layer may be in a liquid phase.

[0035] According to the method for manufacturing a joined body in (12) above, it is possible to more reliably block leakage current between the first superconducting layer and the second superconducting layer by shortening the heat treatment time.

[0036] [Details of Embodiments of the Present Disclosure] Next, details of embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and overlapping descriptions will not be repeated.

[0037] (First Embodiment) A joined body according to the first embodiment will be described. Hereinafter, the joined body according to the first embodiment will be referred to as joined body 100.

[0038] <Configuration of Joined Body 100> The configuration of joined body 100 will be described below.

[0039] FIG. 1 is a cross-sectional view of the bonded body 100. As shown in FIG. 1, the bonded body 100 includes a first substrate 10, a first superconducting layer 20, a second substrate 30, a second superconducting layer 40, and a barrier layer 50. The bonded body 100 may not have the second substrate 30.

[0040] The first substrate 10 has a first main surface 10a. The first substrate 10 is preferably formed of at least one oxide selected from the group consisting of cerium oxide, yttria-stabilized zirconia, lanthanum manganate, sapphire, and strontium titanate. That is, the first substrate 10 is preferably formed of a material having oxygen permeability.

[0041] The first superconducting layer 20 is disposed on the first main surface 10a. The first superconducting layer 20 is formed of REBCO. REBCO is an oxide superconductor represented by REBa2Cu3O x Here, RE is a rare earth element. The rare earth element in the REBCO constituting the first superconducting layer 20 is at least one element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, lutetium, and ytterbium. That is, the rare earth element in the REBCO constituting the first superconducting layer 20 is selected so that the first superconducting layer 20 exhibits superconducting characteristics. Two

[0042]

[0042] The direction of the c-axis of the REBCO constituting the first superconducting layer 20 is along, for example, the normal direction of the first main surface 10a. Hereinafter, the direction of the c-axis of the REBCO may be referred to as the c-axis direction. The c-axis direction of the REBCO constituting the first superconducting layer 20 may be along the direction of the first main surface 10a.

[0043] The second substrate 30 has a second main surface 30a. The second main surface 30a faces the first main surface 10a side. The second substrate 30 is preferably formed of at least one oxide selected from the group consisting of cerium oxide, yttria-stabilized zirconia, lanthanum manganate, sapphire, or strontium titanate. That is, the second substrate 30 is preferably formed of a material having oxygen permeability.

[0044] The second superconducting layer 40 is disposed on the second main surface 30a. The second superconducting layer 40 is formed of REBCO. The rare earth element in the REBCO constituting the second superconducting layer 40 is at least one element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, lutetium, and ytterbium. That is, the rare earth element in the REBCO constituting the second superconducting layer 40 is selected so that the second superconducting layer 40 exhibits superconducting characteristics. Two The c-axis direction of the REBCO constituting the second superconducting layer 40 is, for example, along the normal direction of the second main surface 30a. The c-axis direction of the REBCO constituting the second superconducting layer 40 may be along the direction of the second main surface 30a. The c-axis direction of the REBCO constituting the second superconducting layer 40 is along the c-axis direction of the REBCO constituting the first superconducting layer 20. The a-axis direction of the REBCO constituting the second superconducting layer 40 is along the a-axis direction of the REBCO constituting the first superconducting layer 20. Hereinafter, the direction of the a-axis of the REBCO may be referred to as the a-axis direction.

[0045] The barrier layer 50 is sandwiched between the first superconducting layer 20 and the second superconducting layer 40. From another perspective, the barrier layer 50 is on the first superconducting layer 20, and the second superconducting layer 40 is on the barrier layer 50.

[0046]

[0047] ​The barrier layer 50 is formed of REBCO. The rare earth element in the REBCO constituting the barrier layer 50 is, for example, praseodymium. That is, the rare earth element in the REBCO constituting the barrier layer 50 is selected so that the barrier layer 50 does not exhibit superconducting properties. Note that the content of rare earth elements other than praseodymium in the REBCO constituting the barrier layer 50 is, for example, 1 atomic percent or less. Also, the density of pinholes in the barrier layer 50 is, for example, 5 percent or less. The first superconducting layer 20, the second superconducting layer 40, and the barrier layer 50 constitute a Josephson junction. In other words, the junction body 100 is a Josephson junction body.

[0048] The a-axis direction of the REBCO constituting the barrier layer 50 is along the a-axis direction of the REBCO constituting the first superconducting layer 20. The c-axis direction of the REBCO constituting the barrier layer 50 is along the c-axis direction of the REBCO constituting the first superconducting layer 20. The a-axis direction of the REBCO constituting the barrier layer 50 is along the a-axis direction of the REBCO constituting the second superconducting layer 40. The c-axis direction of the REBCO constituting the barrier layer 50 is along the c-axis direction of the REBCO constituting the second superconducting layer 40. That is, the barrier layer 50 is epitaxially grown from the first superconducting layer 20 and the second superconducting layer 40.

[0049] The thickness of the barrier layer 50 is smaller than the thickness of the first superconducting layer 20 and the thickness of the second superconducting layer 40. The barrier layer 50 thickness is, for example, 100 nm or less.

[0050] <Manufacturing method of the junction body 100> The manufacturing method of the junction body 100 will be described below.

[0051] FIG. 2 is a process diagram showing the manufacturing method of the junction body 100. The manufacturing method of the junction body 100 has a first substrate preparation step S1, a second substrate preparation step S2, a microcrystalline layer formation step S3, and a heat treatment step S4, as shown in FIG. 2.

[0052] 1. In the first substrate preparation step S1, first, a first substrate 10 is prepared. In the first substrate preparation step S1, second, a first superconducting layer 20 is formed on the first main surface 10a. The first superconducting layer 20 is formed, for example, by the MOD (Metal Organic Decomposition ) method. The rare earth element in the REBCO constituting the first superconducting layer 20 is selected so that the first superconducting layer 20 exhibits superconducting characteristics as described above. The temperature at the time of forming the first superconducting layer 20 is, for example, 750°C or higher and 840°C or lower. The c-axis direction of the REBCO constituting the first superconducting layer 20 is along, for example, the direction of the first main surface 10a or the normal direction of the first main surface 10a.

[0053] In the second substrate preparation step S2, first, a second substrate 30 is prepared. In the second substrate preparation step S2, second, a second superconducting layer 40 is formed on the second main surface 30a. The second superconducting layer 40 is formed, for example, by the MOD method. The rare earth element in the REBCO constituting the second superconducting layer 40 is selected so that the second superconducting layer 40 exhibits superconducting characteristics as described above. The temperature at the time of forming the second superconducting layer 40 is, for example, 750°C or higher and 840°C or lower. The c-axis direction of the REBCO constituting the second superconducting layer 40 is along, for example, the direction of the second main surface 30a or the normal direction of the second main surface 30a. In the heat treatment step S4 described later, the first substrate 10 and the second substrate 30 are held so that, for example, the c-axis direction and the a-axis direction of the first superconducting layer 20 are along the c-axis direction and the a-axis direction of the second superconducting layer 40, respectively.

[0054] FIG. 3 is a cross-sectional view of the second substrate 30 after the microcrystalline layer forming step S3 is performed. As shown in FIG. 3, in the microcrystalline layer forming step S3, a microcrystalline layer 60 is formed. The microcrystalline layer 60 is formed on the second superconducting layer 40. The microcrystalline layer 60 is formed of a polycrystal of REBCO. Note that the microcrystalline layer 60 may be formed on the first superconducting layer 20. That is, the microcrystalline layer 60 may be formed on either one of the first superconducting layer 20 and the second superconducting layer 40.

[0055] When forming the microcrystalline layer 60, first, an organic compound film is formed on the second superconducting layer 40 by, for example, the spin coating method. This organic compound film contains the constituent elements of REBCO. Second, a pre-firing is performed on the organic compound film. By this pre-firing, the organic compound film becomes a precursor of REBCO. Hereinafter, the pre-fired organic compound film is referred to as a pre-fired film. Third, after the pre-firing, a heat treatment is performed on the pre-fired film. As a result, the carbides contained in the pre-fired film are decomposed, and a microcrystalline layer 60 containing microcrystals of REBCO is formed.

[0056] In the heat treatment step S4, the barrier layer 50 is formed. In the heat treatment step S4, the first substrate 10 and the second substrate 30 are heated while holding the first substrate 10 and the second substrate 30 in a state where the microcrystalline layer 60 is sandwiched between the first superconducting layer 20 and the second superconducting layer 40. As a result, the REBCO contained in the microcrystalline layer 60 epitaxially grows from the first superconducting layer 20 and the second superconducting layer 40 to form the barrier layer 50. The heating in the heat treatment step S4 is performed in an atmosphere containing oxygen.

[0057] During the heat treatment step S4, at least a part of the microcrystalline layer 60 may be in a liquid phase. The melting point of the REBCO constituting the microcrystalline layer 60 decreases by reducing the oxygen concentration in the atmosphere where heating is performed. Therefore, by adjusting the oxygen concentration in the atmosphere where heating is performed, at least a part of the microcrystalline layer 60 can be brought into a liquid phase during the heat treatment step S4.

[0058] The heating temperature in the heat treatment step S4 is, for example, 800 °C. The oxygen concentration in the atmosphere where heating is performed in the heat treatment step S4 is, for example, 60 ppm when at least a part of the microcrystalline layer 60 is in a liquid phase. The oxygen concentration in the atmosphere where heating is performed in the heat treatment step S4 is, for example, 150 ppm when the microcrystalline layer 60 is not in a liquid phase. The heating time in the heat treatment step S4 is, for example, 1 minute when at least a part of the microcrystalline layer 60 is in a liquid phase. The heating time in the heat treatment step S4 is, for example, 10 minutes when the microcrystalline layer 60 is not in a liquid phase.

[0059] The second substrate 30 may be removed after the heat treatment step S4 is performed. Thus, the bonded body 100 having the structure shown in FIG. 1 is manufactured.

[0060] <Effect of the bonded body 100> The effect of the bonded body 100 will be described below while comparing it with the bonded body according to the comparative example. In the following, the bonded body according to the comparative example is referred to as the bonded body 200.

[0061] FIG. 4 is a cross-sectional view of the bonded body 200. As shown in FIG. 4, the bonded body 200 has a first substrate 10, a first superconducting layer 20, a second superconducting layer 40, and a barrier layer 50, similar to the bonded body 100.

[0062] However, in the manufacturing process of the bonded body 200, first, the barrier layer 50 is epitaxially grown on the first substrate 10, and second, the second superconducting layer 40 is formed on the barrier layer 50.

[0063] Since the thickness of the second superconducting layer 40 is larger than the thickness of the barrier layer 50, in the manufacturing process of the bonded body 200, heating for forming the second superconducting layer 40 requires a long time, and the rare earth elements in the first superconducting layer 20 and the rare earth elements in the second superconducting layer 40 diffuse into the barrier layer 50. As a result, the REBCO constituting the barrier layer 50 is partially superconducting, and a leakage current flows between the first superconducting layer 20 and the second superconducting layer 40. That is, in the bonded body 200, pinholes are formed in the barrier layer 50, and a leakage current flows between the first superconducting layer 20 and the second superconducting layer 40.

[0064] On the other hand, in the manufacturing process of the joined body 100, heating for forming the second superconducting layer 40 is not performed after the barrier layer 50 is formed. Therefore, it is possible to prevent the rare earth elements in the first superconducting layer 20 and the rare earth elements in the second superconducting layer 40 from diffusing into the barrier layer 50 to form pinholes in the barrier layer 50 due to the heating when the second superconducting layer 40 is formed. Therefore, according to the joined body 100, the barrier layer 50 can block leakage current between the first superconducting layer 20 and the second superconducting layer 40.

[0065] When at least a part of the microcrystalline layer 60 is in a liquid phase during the heat treatment step S4, the time required for forming the barrier layer 50 is further shortened. Therefore, in this case, it is possible to more reliably prevent the rare earth elements in the first superconducting layer 20 and the rare earth elements in the second superconducting layer 40 from diffusing into the barrier layer 50 and the REBCO constituting the barrier layer 50 from becoming superconducting.

[0066] <Modification> FIG. 5 is a cross-sectional view of the joined body 100 according to the modification. As shown in FIG. 5, the joined body 100 may further include a first metal substrate 70a and a second metal substrate 70b. The first metal substrate 70a and the second metal substrate 70b are, for example, clad materials obtained by laminating stainless steel, copper, and nickel. In this example, the first substrate 10 and the second substrate 30 function as a first intermediate layer 80a and a second intermediate layer 80b. The first intermediate layer 80a and the second intermediate layer 80b are respectively disposed on the first metal substrate 70a and the second metal substrate 70b. Note that the joined body 100 may not have the second metal substrate 70b and the second intermediate layer 80b.

[0067] (Second Embodiment) The joined body according to the second embodiment will be described. Here, the differences from the joined body 100 will be mainly described, and repeated descriptions will not be repeated. In the following, the joined body according to the second embodiment will be referred to as the joined body 300.

[0068] <Configuration of the joined body 300> The configuration of the joined body 300 will be described below.

[0069] FIG. 6 is a cross-sectional view of the joined body 300. As shown in FIG. 6, the joined body 300 has a first substrate 10, a first superconducting layer 20, a second substrate 30, a second superconducting layer 40, and a barrier layer 50. In this regard, the configuration of the joined body 300 is common to the configuration of the joined body 100.

[0070] However, the configuration of the joined body 300 is different from the configuration of the joined body 100 with respect to the details of the first superconducting layer 20, the second superconducting layer 40, and the barrier layer 50.

[0071] In the joined body 300, similar to the joined body 100, the c-axis direction of the REBCO constituting the second superconducting layer 40 is along the c-axis direction of the REBCO constituting the first superconducting layer 20. However, in the joined body 300, the a-axis direction of the REBCO constituting the second superconducting layer 40 is different from the a-axis direction of the REBCO constituting the first superconducting layer 20.

[0072] In the joined body 300, the barrier layer 50 has a first layer 51 and a second layer 52. The first layer 51 is epitaxially grown from the first superconducting layer 20. The second layer 52 is epitaxially grown from the second superconducting layer 40. As described above, in the joined body 300, since the a-axis direction of the REBCO constituting the second superconducting layer 40 is different from the a-axis direction of the REBCO constituting the first superconducting layer 20, the a-axis direction of the REBCO constituting the first layer 51 is different from the a-axis direction of the REBCO constituting the second layer 52. That is, in the joined body 300, lattice matching is not achieved at the interface between the first layer 51 and the second layer 52.

[0073] Note that, in the joined body 300, the rare earth element in the REBCO constituting the barrier layer 50 may be selected so that the barrier layer 50 exhibits superconducting characteristics. That is, in the joined body 300, the rare earth elements in the REBCO constituting the first superconducting layer 20, the second superconducting layer 40, and the barrier layer 50 are yttrium, lanthanum, neodymium, samarium, europium, gadolinium TwoIt may be at least one or more elements selected from the group consisting of um, dysprosium, holmium, erbium, thulium, lutetium and ytterbium. In the bonded body 300, the rare earth element in the REBCO constituting the barrier layer 50 may be praseodymium.

[0074] <Method for manufacturing the bonded body 300> The method for manufacturing the bonded body 300 will be described below.

[0075] The method for manufacturing the bonded body 300 includes a first substrate preparation step S1, a second substrate preparation step S2, a microcrystalline layer formation step S3, and a heat treatment step S4. In this regard, the method for manufacturing the bonded body 300 is common to the method for manufacturing the bonded body 100.

[0076] However, in the second substrate preparation step S2 of the method for manufacturing the bonded body 300, the second superconducting layer 40 is formed such that the a-axis direction of the second superconducting layer 40 is different from the a-axis direction of the first superconducting layer 20. Further, in the heat treatment step S4 of the method for manufacturing the bonded body 300, the first layer 51 epitaxially grows from the first superconducting layer 20 and the second layer 52 epitaxially grows from the second superconducting layer 40, thereby forming the barrier layer 50. In these regards, the method for manufacturing the bonded body 300 is different from the method for manufacturing the bonded body 100.

[0077] <Effect of the bonded body 300> In the bonded body 300, since the a-axis direction of the REBCO constituting the first layer 51 is different from the a-axis direction of the REBCO constituting the second layer 52, the superconducting current flowing through the first superconducting layer 20 cannot pass between the first layer 51 and the second layer 52. Similarly, the superconducting current flowing through the second superconducting layer 40 also cannot pass between the first layer 51 and the second layer 52. Therefore, also with the bonded body 300, it is possible to block the leakage current between the first superconducting layer 20 and the second superconducting layer 40 by the barrier layer 50.

[0078] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the above-described embodiments, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Explanation of Reference Numerals

[0079] 10 First substrate, 10a First main surface, 20 First superconducting layer, 30 Second substrate, 30a Second main surface, 40 Second superconducting layer, 50 Barrier layer, 51 First layer, 52 Second layer, 60 Microcrystalline layer, 70a First metal substrate, 70b Second metal substrate, 80a First intermediate layer, 80b Second intermediate layer, 100, 200, 300 Bonded body, S1 First substrate preparation step, S2 Second substrate preparation step, S3 Microcrystalline layer formation step, S4 Heat treatment step.

Claims

1. A first superconducting layer, A barrier layer disposed on the first superconducting layer, And a second superconducting layer disposed on the barrier layer, The first superconducting layer, the barrier layer, and the second superconducting layer are formed of REBCO, Leakage current from one of the first superconducting layer and the second superconducting layer to the other of the first superconducting layer and the second superconducting layer is blocked by the barrier layer, The barrier layer has a first layer disposed on the first superconducting layer and a second layer disposed on the first layer, The c-axis direction of the REBCO constituting the first layer is along the c-axis direction of the REBCO constituting the second layer, The a-axis direction of the REBCO constituting the first layer is different from the a-axis direction of the REBCO constituting the second layer, a bonded body.

2. The rare earth elements in the REBCO constituting the first superconducting layer and the second superconducting layer are selected such that the first superconducting layer and the second superconducting layer exhibit superconducting properties, The rare earth elements in the REBCO constituting the barrier layer are selected such that the barrier layer does not exhibit superconducting properties, the bonded body according to claim 1.

3. The rare earth elements in the REBCO constituting the first superconducting layer and the second superconducting layer are at least one or more elements selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, lutetium, and ytterbium, The rare earth element in the REBCO constituting the barrier layer is praseodymium, the bonded body according to claim 2.

4. The barrier layer is epitaxially grown from the first superconducting layer and the second superconducting layer, the bonded body according to claim 2 or claim 3.

5. The first layer is epitaxially grown from the first superconducting layer, The second layer is epitaxially grown from the second superconducting layer, The c-axis direction of the REBCO constituting the first superconducting layer is along the c-axis direction of the REBCO constituting the second superconducting layer, The a-axis direction of the REBCO constituting the first superconducting layer is different from the a-axis direction of the REBCO constituting the second superconducting layer. The bonded body according to claim 1.

6. The rare earth element in the REBCO constituting the first superconducting layer, the second superconducting layer and the barrier layer is at least one element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, lutetium and ytterbium. The bonded body according to claim 1 or claim 5.

7. Further comprising a substrate, The first superconducting layer is disposed on the substrate, The substrate is formed of at least one oxide selected from the group consisting of cerium oxide, yttria-stabilized zirconia, lanthanum manganate, sapphire and strontium titanate. The bonded body according to any one of claims 1 to 6.

8. A metal substrate, Further comprising an intermediate layer disposed on the metal substrate, The first superconducting layer is disposed on the intermediate layer, The intermediate layer is formed of at least one oxide selected from the group consisting of cerium oxide, yttria-stabilized zirconia, lanthanum manganate, sapphire and strontium titanate. The bonded body according to any one of claims 1 to 6.

9. A first superconducting layer, A barrier layer disposed on the first superconducting layer, It includes a second superconducting layer disposed on the barrier layer. The first superconducting layer, the barrier layer, and the second superconducting layer are formed of REBCO. Leakage current from one of the first superconducting layer and the second superconducting layer to the other of the first superconducting layer and the second superconducting layer is blocked by the barrier layer. It further includes a substrate. The first superconducting layer is disposed on the substrate. The c-axis direction of the REBCO constituting the first superconducting layer is along the direction of the main surface of the substrate on the first superconducting layer side or the normal direction of the main surface, the joined body.

10. A step of forming a first superconducting layer on a first substrate; A step of forming a second superconducting layer on a second substrate; A step of forming a microcrystalline layer on either the first superconducting layer or the second superconducting layer; A step of heating the first substrate and the second substrate while holding the first substrate and the second substrate such that the microcrystalline layer is sandwiched between the first superconducting layer and the second superconducting layer. The first superconducting layer and the second superconducting layer are formed of REBCO. The microcrystalline layer is formed of a polycrystal of REBCO, a method for manufacturing a joined body.

11. In the step of heating the first substrate and the second substrate, at least a part of the microcrystalline layer is in a liquid phase, the method for manufacturing a joined body according to Claim 10.

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