JP2015213006A - Connection structure and connection method for superconducting wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively perform oxygen annealing.SOLUTION: Provided is a connection structure 100 of superconducting wire rods in which one side of a base material 1 is connected with the mutual connection edge parts of superconducting wire rods 10A, 10B formed with an oxide superconducting conductor layer 3 so as to be pasted each other, the oxide superconducting layers of the two superconducting wire rods are joined so as to be confronted each other, and an opening part 13 is provided at a depth not passing through each superconducting layer at a face 12 on the reverse side to each oxide superconducting layer in the base material within the joining range of either or both the oxide superconducting wire rods.

Description

  The present invention relates to a superconducting wire connection structure and a connection method.

In recent years, oxide superconductors such as YBCO (yttrium) and Bi (bismuth) oxides have attracted attention as oxide superconductors whose critical temperature (Tc) is higher than liquid nitrogen temperature (about 77K). .
This high-temperature oxide superconducting wire is known in which a superconducting conductor layer is formed by forming an oxide superconducting film on a long and flexible substrate such as a metal. An intermediate layer may be provided between the substrate and the superconducting conductor layer as necessary.

  As a method for connecting the superconducting wires, Patent Document 1 discloses an MOD based on a MOD method (Metal Organic Deposition method / Organic metal deposition method) by exposing an oxide superconductor contained in the sheath of two superconducting wires to be connected. There is a method of connecting two superconducting wires through a superconducting film formed from a MOD liquid by applying a liquid to an exposed surface, bonding the exposed surfaces together, and baking.

  In Patent Document 2, the superconducting conductor layer of the two superconducting wires in which the superconducting conductor layer is formed on the upper surface of the substrate via the buffer layer is exposed, and the superconducting conductor layers are in close contact with each other. There is a method in which two superconducting wires are connected by heating to the melting point of the layer, melting and diffusing the superconducting conductor layer.

JP 2009-016253 A Japanese Patent No. 5214744

Since both the connection methods of Patent Document 1 and Patent Document 2 perform heating at the time of joining the superconducting conductor layers, when the superconducting conductor layer is an oxide superconducting conductor layer such as YBa ₂ Cu ₃ O _7-x In some cases, oxygen escapes from the superconducting conductor layer after joining and the superconductivity is greatly deteriorated.
For this reason, it is necessary to perform oxygen annealing in which the connecting portion of the superconducting wire is oxidized in an oxygen atmosphere at about 500 ° C.
However, in the connection structure of the superconducting wire, the superconducting conductor layer is sandwiched between base materials, and the base material is often formed of a metal or the like that has almost no oxygen permeability.
For this reason, it is difficult for oxygen to reach the inner part sandwiched between the base material as a barrier layer, and sufficient oxygen annealing cannot be performed, or oxygen annealing requires a very long time. There was a problem.

  An object of the present invention is to provide a connection structure and a connection method capable of effectively performing oxygen annealing.

The invention described in claim 1
A superconducting wire connecting structure in which the connecting end portions of the superconducting wires having the oxide superconducting conductor layer formed on one side of the base material are polymerized and connected,
The oxide superconducting conductor layers of the two superconducting wires are joined face to face,
An opening is provided at a depth not penetrating the oxide superconducting conductor layer on a surface opposite to the oxide superconducting conductor layer in the base material within a bonding range of one or both of the superconducting wires. Features.

The invention described in claim 2 is the superconducting wire connecting structure according to claim 1,
One end and the other end are provided on both sides of the opening with reinforcing members individually connected to the two superconducting wires.

The invention according to claim 3 is the connection structure of the superconducting wire according to claim 2,
The reinforcing member is characterized in that one end and the other end of the reinforcing member are joined to the opposite side of the oxide superconducting conductor layer in the base material of the two superconducting wires.

The invention according to claim 4
An oxide superconducting conductor layer is formed on one side of the substrate, and two superconducting wires facing each other are connected to each other by a connecting superconducting wire in which an oxide superconducting conductor layer is formed on one side of the substrate. A superconducting wire connection structure that is bridge-connected,
The oxide superconducting conductor layer of the two superconducting wires and the oxide superconducting conductor layer of the connecting superconducting wire are joined face to face,
The oxide superconducting conductor on the surface opposite to the oxide superconducting conductor layer in the base material within the joining range of one or both of the two superconducting wires and the connecting superconducting wire. An opening is provided at a depth that does not penetrate the layer.

The invention according to claim 5 is the superconducting wire connecting structure according to any one of claims 1 to 4,
The superconducting wire comprises an intermediate layer between the base material and the oxide superconducting conductor layer,
The opening is formed up to an intermediate layer.

The invention according to claim 6 is the connection structure of the superconducting wire according to any one of claims 1 to 5,
The opening is formed in a groove shape.

The invention according to claim 7 is the superconducting wire connecting structure according to any one of claims 1 to 5,
A plurality of the openings are formed side by side.

The invention described in claim 8
A superconducting wire connecting method in which the connection ends of the superconducting wires formed with an oxide superconducting conductor layer on one side of the base material are polymerized and connected,
An exposing step of exposing the oxide superconducting conductor layer of the two superconducting wires;
A joining step in which the oxide superconducting conductor layers of the two superconducting wires are joined face to face;
An opening that forms an opening at a depth not penetrating the oxide superconducting conductor layer by etching on a surface opposite to the oxide superconducting conductor layer in the base material within a bonding range of one or both of the superconducting wires. Process,
And an oxygen annealing step for the oxide superconducting conductor layer.

The invention according to claim 9 is the method of connecting superconducting wires according to claim 8,
The joining step includes a step of disposing a precursor of the oxide superconducting conductor on one or both of the oxide superconducting conductor layers of the two superconducting wires, and a step of firing the precursor of the oxide superconducting conductor; It is characterized by including.

The invention according to claim 10 is:
For connection in which an oxide superconducting conductor layer is formed on one side of a base material in a state in which the connection ends of two superconducting wires having an oxide superconducting conductor layer formed on one side of the base material are butted together A superconducting wire connecting method for bridge connection with a superconducting wire of
An exposing step of exposing the oxide superconducting conductor layer of the two superconducting wires;
A joining step of joining the oxide superconducting conductor layer of the two superconducting wires and the oxide superconducting conductor layer of the superconducting wire for connection facing each other;
Etching is performed on the surface opposite to the oxide superconducting conductor layer in the base material within the bonding range of one or both of the two superconducting wires and the connecting superconducting wires. An opening step of forming an opening at a depth not penetrating the physical superconductor layer;
And an oxygen annealing step for the oxide superconducting conductor layer.

The invention according to claim 11 is the method of connecting superconducting wires according to claim 10,
In the joining step, a precursor of the oxide superconducting conductor is disposed on one or both of the oxide superconducting conductor layer of the two superconducting wires and the oxide superconducting conductor layer of the connecting superconducting wire. And a step of firing the precursor of the oxide superconducting conductor.

  In the above invention, oxygen annealing can be effectively performed by the above configuration.

It is a perspective view of a superconducting wire. 2A is a cross-sectional view of a superconducting wire connecting structure according to the first embodiment along the line V-V in FIG. 2B, and FIG. 2B is a plan view. 3 (A) to 3 (E) are cross-sectional views showing a superconducting wire connecting method in the order of steps. It is sectional drawing which shows the example of the opening part formed by laser processing. FIG. 5A is a side view showing an example in which a reinforcing member is added to the superconducting wire connection structure, and FIG. 5B is a view of the other end of the reinforcing member as seen from the second superconducting wire side. It is sectional drawing which shows the example which formed the opening part in both the 1st and 2nd superconducting wire. It is sectional drawing which shows the example which bridge-connected the 1st and 2nd superconducting wire with the 3rd superconducting wire. 8A to 8E are cross-sectional views showing a method of connecting superconducting wires in the order of steps.

[First embodiment]
Hereinafter, a preferred first embodiment for carrying out the present invention will be described with reference to the drawings. However, the embodiments described below are given various technically preferable limitations for carrying out the present invention, but the scope of the present invention is not limited to the following embodiments and illustrated examples. In the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and repeated descriptions are omitted as appropriate. Furthermore, it should be noted that the drawings are schematic, and dimensional relationships between elements may differ from actual ones. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included.

[Superconducting wire]
In this embodiment, a superconducting wire connecting structure will be described.
FIG. 1 is a perspective view of a superconducting wire according to the first embodiment of the present invention.
As shown in FIG. 1, a superconducting wire 10 is placed on one main surface (hereinafter referred to as a film-forming surface 11) in the thickness direction of a substrate 1 for superconducting film formation (hereinafter referred to as “base material 1”). Layer 2, oxide superconducting conductor layer 3, and stabilization layer 4 are laminated in this order, and the surface opposite to the film formation surface 11 of the substrate 1 (hereinafter referred to as “back surface 12”) is also stabilized. Layer 4 is formed. That is, the superconducting wire 10 has a laminated structure including a stabilizing layer 4, a base material 1, an intermediate layer 2, an oxide superconducting conductor layer 3 (hereinafter referred to as “superconducting conductor layer 3”), and a stabilizing layer 4. Yes.

As the substrate 1, a low magnetic metal substrate or ceramic substrate is used. As the material of the metal substrate, for example, a metal such as Co, Cu, Cr, Ni, Ti, Mo, Nb, Ta, W, Mn, Fe, and Ag, which is excellent in strength and heat resistance, or an alloy thereof is used. . In particular, from the viewpoint of excellent corrosion resistance and heat resistance, it is preferable to use Ni-based alloys such as Hastelloy (registered trademark) and Inconel (registered trademark), or Fe-based alloys such as stainless steel.
Various ceramics may be arranged on these various metal materials. Moreover, as a material of the ceramic substrate, for example, MgO, SrTiO ₃ , yttrium stabilized zirconia, or the like is used. In addition, sapphire may be used as a base material.

The film formation surface 11 is a substantially smooth surface, and for example, the surface roughness of the film formation surface 11 is preferably 10 nm or less.
The surface roughness is the arithmetic average roughness Ra in the “amplitude average parameter in the height direction” of the surface roughness parameter defined in JISB-0601-2001.

The intermediate layer 2 is a layer for realizing, for example, high biaxial orientation in the superconducting conductor layer 3. For such an intermediate layer 2, for example, physical characteristic values such as a coefficient of thermal expansion and a lattice constant indicate intermediate values between the substrate 1 and the superconductor constituting the superconducting conductor layer 3.
The intermediate layer 2 may have a single layer structure or a multilayer structure. In the case of a multilayer structure, the number and types of layers are not limited, but a bed layer containing amorphous Gd ₂ Zr ₂ O _7-δ (δ is an oxygen non-stoichiometric amount), Al ₂ O _3, Y ₂ O _3, or the like. And a forced alignment layer formed by IBAD (Ion Beam Assisted Deposition) method including crystalline MgO and the like, and an LMO layer including LaMnO _{3 + δ} (δ is an oxygen non-stoichiometric amount) are sequentially stacked. May be. Further, a cap layer containing CeO ₂ or the like may be further provided on the LMO layer.
The thickness of each of the above layers is 30 nm for the LMO layer, 40 nm for the MgO layer for forced alignment layer, 7 nm for the Y ₂ O ₃ layer for bed, and 80 nm for the Al ₂ O ₃ layer. These numerical values are only examples.
In addition, the intermediate layer 2 preferably has an Al ₂ O ₃ (alumina) layer regardless of whether the intermediate layer 2 has a single layer structure or a multilayer structure.

A superconducting conductor layer 3 is laminated on the surface of the intermediate layer 2. The superconducting conductor layer 3 preferably contains an oxide superconductor, particularly a copper oxide superconductor. As the copper oxide superconductor, REBa ₂ Cu ₃ O _7-δ (hereinafter referred to as RE superconductor) as a high-temperature superconductor is preferable. The RE in the RE-based superconductor is a single rare earth element or a plurality of rare earth elements such as Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu. Y is preferable because it is difficult to cause substitution with the Ba site. Further, δ is an oxygen non-stoichiometric amount and is, for example, 0 or more and 1 or less, and is preferably closer to 0 from the viewpoint that the superconducting transition temperature is high. The oxygen non-stoichiometric amount may be less than 0, that is, take a negative value when high-pressure oxygen annealing or the like is performed using an apparatus such as an autoclave.

The stabilization layers 4, 4 cover the surface of the superconducting conductor layer 3 and the back surface 12 of the base material 1, but more preferably cover the entire periphery of the base material 1, the intermediate layer 2, and the superconducting conductor layer 3. preferable.
The stabilizing layers 4 and 4 may have a single layer structure or a multilayer structure. In the case of a multilayer structure, the number and types of the layers are not limited, but a silver stabilization layer made of silver and a copper stabilization layer made of copper may be laminated in order.
In the present embodiment, the stabilization layers 4 and 4 cover the surface of the superconducting conductor layer 3 and the back surface 12 of the base material 1, but the present invention is not limited to this, and at least the surface of the superconducting conductor layer 3 may be covered. That's fine.

[Connection structure of superconducting wire]
As shown in FIG. 2 (A), the superconducting wire connecting structure 100 according to the present embodiment is a connecting method (described later) in which the connecting ends of the first and second superconducting wires 10A and 10B are overlapped. ). The first and second superconducting wires 10A and 10B have the same structure as the superconducting wire 10, and the same reference numerals as those of the superconducting wire 10 are used for the respective layers 1 to 4.

In this connection structure 100, the exposed planes of the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B are joined face to face, and are attached to the back surface 12 of the base 1 of the second superconducting wire 10B. The opening 13 is provided at a depth that does not penetrate the superconducting conductor layers 3 and 3.
As shown in FIG. 2B, the opening 13 is substantially rectangular in plan view, and a plurality of openings 13 are formed in two rows along the longitudinal direction of the substrate 1.
Each opening 13 is formed with a depth reaching from the back surface 12 of the substrate 1 to the intermediate layer 2.

[Connection method of superconducting wire]
With respect to the connection structure 100 described above, the connection method will be described in the order of steps based on FIGS. 3 (A) to 3 (E).
First, as shown in FIG. 3A, first and second superconducting wires 10A and 10B are prepared. In addition, in FIG. 3 (A) and FIG. 3 (B), illustration of the 2nd superconducting wire 10B is abbreviate | omitted.
Then, as shown in FIG. 3 (B), on the connection end portions side of the first and second superconducting wires 10A and 10B, the stabilization layers 4 and 4 on the superconducting conductor layer 3 side and on the back surface 12 side of the substrate 1. Then, the superconducting conductor layers 3 and 3 are exposed (exposure process). The removal of the stabilization layer 4 is performed by mechanical polishing, chemical polishing, or a combination thereof.
Further, it is desirable that the surface roughness of the superconducting conductor layer 3 exposed by peeling of the stabilizing layer 4 is made smaller (for example, about 10 nm) in order to satisfactorily join the superconducting conductor layers.

Next, as shown in FIG. 3C, the exposed surfaces of the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B are arranged facing each other so that the superconducting conductor layers 3 and 3 Are joined (joining step).
Here, the superconducting conductors 3A and 3B of the first and second superconducting wires 10A and 10B are joined by forming a superconducting conductor (not shown) by the MOD method (Metal Organic Deposition method / Organic metal deposition method). .
For this reason, the joining step is performed based on the MOD method on one or both of the surface of the superconducting conductor layer 3 of the first superconducting conductor layer 10A and the surface of the superconducting conductor layer 3 of the second superconducting conductor layer 10B. A step of applying a MOD liquid to be a precursor of the superconducting conductor.
The MOD liquid contains, for example, RE (rare earth elements such as Y (yttrium), Gd (gadolinium), Sm (samarium), and Ho (holmium)), Ba, and Cu in a ratio of about 1: 2: 3. Acetylacetonate MOD solutions are used.

Further, the bonding step includes a preliminary firing step for removing an organic component contained in the MOD liquid applied to one or both of the first superconducting wire 10A and the second superconducting wire 10B, A main firing step for joining the superconducting conductor layers 3 and 3 by epitaxial growth at the interface between the superconducting conductor layers 3 and 3 of the second superconducting wires 10A and 10B is included.
About the said temporary baking process, heat processing is performed at a temperature range of 400 degreeC or more and 500 degrees C or less, pressurizing the junction part of 1st and 2nd superconducting wire 10A, 10B in the range of 10-100 MPa.
Further, in the main firing step, heat treatment is performed in a temperature range of 780 ° C. or higher and 830 ° C. or lower while pressurizing the joining portion of the first and second superconducting wires 10A and 10B in the range of 10 to 100 MPa.
In addition, both of these pressure conditions and temperature conditions are examples, and these numerical ranges are not limited.

Next, an opening 13 is formed in the back surface 12 of the base material 1 of the second superconducting wire 10B with a depth reaching the intermediate layer 2 by etching (opening step).
The etching includes a mask forming process for leaving a portion other than the opening 13 of the base material 1 and a removing process for partially removing the base material 1 according to the mask.

  In the mask process, as shown in FIG. 3D, the entire connecting portion of the first and second superconducting wires 10A and 10B is covered with an etching resist 51, and the etching resist is formed according to the formation pattern of the plurality of openings 13. 51 is exposed with an energy beam having a predetermined short wavelength. Then, the resist in the exposed portion is removed with a developer for the etching resist 51 to form a mask. Although the case where the etching resist is a positive type is illustrated, a negative type etching resist 51 may be used. In that case, portions other than the formation pattern of the plurality of openings 13 are exposed.

In the removing step, a portion other than the mask portion by the etching resist 51 is immersed in an etching solution, and a plurality of openings 13 are formed from the back surface 12 side of the substrate 1. An etching solution that dissolves the substrate 1 and does not dissolve the intermediate layer 2 is used. Thereby, the progress of dissolution by the etching solution can be stopped by the intermediate layer 2.
For example, when the substrate 1 is made of Hastelloy (registered trademark), which is a NiCr alloy, nitric acid is 20 to 30%, sulfuric acid is 1 to 5%, and hydrogen peroxide is 0.5 to 2%. When the etching solution contained is used, suitable opening formation can be performed. In addition, the said numerical range is an example and can select a different value suitably.
As described above, when the intermediate layer 2 includes an Al ₂ O ₃ layer, it does not dissolve in the etching solution, and therefore, at least the opening 13 does not proceed to the superconducting conductor layer 3 side than the Al ₂ O ₃ layer.

Next, as shown in FIG. 3E, the etching resist 51 is removed, and an oxygen annealing step is performed in which the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B are doped with oxygen. Is called. This oxygen annealing step is performed by accommodating the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B in an oxygen atmosphere in a temperature range of 350 ° C. or higher and 500 ° C. or lower for a predetermined time. .
And the connection structure 100 of a superconducting wire is formed by these processes.

[Technical effects of the first embodiment]
The superconducting wire connecting structure 100 is formed on the back surface 12 of the base material 1 of the second superconducting wire 10B out of the first and second superconducting wires 10A and 10B to which the superconducting conductor layers 3 and 3 are joined face to face. A plurality of openings 13 reaching the intermediate layer 2 are provided.
For this reason, when the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B are joined and oxygen annealing is performed, oxygen is not superposed by the base material 1 and the oxygen is superconducting through the openings 13. 3 and 3, and can effectively promote oxidation. Therefore, the superconductivity of the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B can be maintained high. In addition, the time required for oxygen annealing can be shortened.

  Further, since a plurality of openings 13 are formed side by side along the longitudinal direction of the second superconducting wire 10B, the strength of the substrate 1 can be adjusted to an appropriate range by appropriately adjusting the interval. Is possible.

Moreover, since each opening 13 is formed by etching, it is possible to form the opening 13 that does not penetrate the superconducting conductor layer 3.
For example, it is possible to form the opening by laser processing. In this case, the opening 13a is also formed through the intermediate layer 2 and the superconducting conductor layer 3 as shown in FIG. As described above, in the case of the opening 13a through which the superconducting conductor layer 3 penetrates, even when oxygen is supplied into the opening 13a during the oxygen annealing, the superconducting conductor layer 3 has a minute size inside the opening 13a. Since the end face 3a is only exposed to oxygen, the oxidation cannot be promoted sufficiently, and the superconductivity of the superconducting conductor layers 3 and 3 of the connection structure cannot be maintained high.
On the other hand, since the opening 13 formed by etching has a wide inner bottom surface, it is possible to sufficiently promote the oxidation of the superconducting conductor layer 3 as compared with the processing by laser, and the superconducting conductor layers 3 and 3 of the connection structure 100 can be promoted. It is possible to maintain higher superconductivity.

In addition, when the bed layer of the intermediate layer 2 includes Al ₂ O ₃ , etching can be performed up to this Al ₂ O ₃ layer, and Al ₂ O ₃ can be compared with other metals and the like. Since the oxygen permeability is excellent, the oxidation of the superconducting conductor layer 3 can be promoted sufficiently, and the superconducting properties of the superconducting conductor layers 3 and 3 of the connection structure can be maintained higher.

The superconducting conductor layers 3 and 3 are joined by applying a MOD solution as a precursor of an oxide superconducting conductor to one or both of the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B. And a step of firing the precursor of the superconducting conductor.
Thereby, in a joining process, a superconducting conductor can be formed between the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B, and the superconducting critical current between the superconducting conductor layers 3 and 3 can be formed. It is possible to connect with a sufficiently large density.

  In the said embodiment, it is set as the structure by which the stabilization layers 4 and 4 of the superconducting conductor layer 3 side and the back surface 12 side of the base material 1 were removed in the connection edge part side of 1st and 2nd superconducting wire 10A, 10B. However, it is not limited to this. For example, when removing only the base material 1 of the second superconducting wire 10B by etching, the stabilizing layer on the back surface 12 side of the base material 1 of the first superconducting wire 10A may be left without being removed.

[Reinforcing member]
In the superconducting wire connecting structure 100, the superconducting conductor layers 3 and 3 are connected to each other by joining the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B. Is easy to peel off, and as shown in FIG. 5, a reinforcing member 60 may be added to the superconducting wire connection structure 100 to enhance the connection strength.

In the reinforcing member 60, one end 61 and the other end 62 are individually connected to the first and second superconducting wires 10A and 10B, avoiding the openings 13 formed in the second superconducting wire 10B. ing.
One end portion 61 of the reinforcing member 60 has a long plate shape, and the flat plate surface is soldered to the outer surface of the stabilization layer 4 formed on the back surface 12 of the base 1 of the first superconducting wire 10A. It is joined. A symbol H in FIG. 5 indicates solder.

The other end portion 62 of the reinforcing member 60 includes a pair of arm portions 63 and 63 that wrap around the outer surface of the stabilization layer 4 formed on the back surface 12 of the base material 1 of the second superconducting wire 10B. The inner side surfaces of the parts 63 and 63 are joined to the outer side surface of the stabilization layer 4 by soldering.
The other end 62 of the reinforcing member 60 is not joined to the stabilizing layer 4 on the superconducting conductor layer 3 side of the second superconducting wire 10B, and a gap is provided to maintain a non-contact state. When the other end 62 of the reinforcing member 60 is joined to the stabilization layer 4 on the superconducting conductor layer 3 side, the superconductivity is passed through the stabilization layer 4 when the first and second superconducting wires 10A and 10B are under tension. There is a possibility that the conductor layer 3 is peeled off or broken. Therefore, the other end portion 62 of the reinforcing member 60 is joined to the stabilization layer 4 on the back surface 12 side of the substrate 1 that is not easily affected by tension.

Further, the other end portion 62 of the reinforcing member 60 is joined to a position farther from the connection end portion of the second superconducting wire 10B than the position where the plurality of openings 13 are formed. This prevents the joint portion of the other end 62 of the reinforcing member 60 from closing the opening 13.
In addition, when the opening part 13 is formed also in the base material 1 of 10 A of 1st superconducting wire like the example mentioned later (refer FIG. 6), the one end part 61 of the reinforcement member 60 is the 2nd superconducting wire. It is desirable to join the connecting end of 10B to a position away from the position where the plurality of openings 13 are formed.

[Example with openings on both sides]
Moreover, although the case where the opening part 13 mentioned above was provided only in the 2nd superconducting wire 10B was illustrated, as shown in FIG. 6, you may form the opening part 13 also in the 1st superconducting wire 10A. Also in this case, a plurality of openings 13 are formed from the back surface 12 of the base 1 of the first superconducting wire 10A to the intermediate layer 2.
As a result, during the oxygen annealing, oxygen is also supplied from the opening 13 on the first superconducting wire 10A side to the superconducting conductor layers 3 and 3 to promote oxidation more effectively. It becomes possible to maintain superconductivity even higher. In addition, the time required for oxygen annealing can be further shortened.
In addition, since the intensity | strength of each base material 1 and 1 falls when both the 1st and 2nd superconducting wire 10A, 10B form the opening part 13, the reinforcement member 60 mentioned above is each superconducting conductor layer. It is also more effective for protecting 3,3.

[Second Embodiment]
In the superconducting wire connecting structure 100 described above, the connecting ends of the first and second superconducting wires 10A and 10B are overlapped and the superconducting conductor layers 3 and 3 are connected face to face. It is not limited to.
In the second embodiment, a superconducting wire connection structure 100C in the case where the first and second superconducting wires 10A and 10B are bridge-connected using a third superconducting wire 10C which is a superconducting wire for connection is illustrated. .

As shown in FIG. 7, the superconducting wire connecting structure 100 </ b> C is a third superconducting wire that is connected to the first and second superconducting wires 10 </ b> A and 10 </ b> B individually by overlapping the connecting ends at both ends thereof. 10C, and the third superconducting wire 10C is provided with an opening 13C.
Note that the opening 13C may be provided on the first and second superconducting wires 10A and 10B.
Further, in this superconducting wire connecting structure 100C, the stabilizing layer 4D extends across the stabilizing layers 4 and 4 on the back surfaces 12 and 12 of the bases 1 and 1 of the first and second superconducting wires 10A and 10B. It is desirable to attach and reinforce the reinforcing wire 10D having the base 1D.

[Connection method of superconducting wire]
FIG. 8 shows a superconducting wire connecting method based on the superconducting wire connecting structure 100C. Such a connection method will be described in the order of steps.
First, as shown in FIG. 8A, first and second superconducting wires 10A and 10B are prepared.
Then, as shown in FIG. 8 (B), the stabilization layer 4 on the superconducting conductor layer 3 side is removed on the connecting end side of the first and second superconducting wires 10A and 10B, and the superconducting conductor layer 3, 3 is exposed (exposure process). The removal of the stabilization layer 4 is performed by mechanical polishing, chemical polishing, or a combination thereof.
The stabilization layer 4 on the back surface 12 side of the base material 1 is left without being removed in order to attach the reinforcing base material 1C shown in FIG.
It should be noted that the surface roughness of the exposed superconducting conductor layer 3 should be reduced as in the case of the superconducting wire connection structure 100.

  Next, as shown in FIG. 8C, the superconducting conductor layer 3C of the third superconducting wire 10C and the exposed superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B face each other. Thus, the third superconducting wire 10C is disposed. The third superconducting wire 10C includes a base material 1C, an intermediate layer 2C, and a superconducting conductor layer 3C, which are the base material 1 and the intermediate layer 2 of the first and second superconducting wires 10A and 10B. The superconducting conductor layer 3 is made of the same material.

Then, the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B and the superconducting conductor layer 3C of the third superconducting wire 10C are joined (joining step).
For joining the superconducting conductor layers 3 and 3 of the first and second superconducting wires 10A and 10B and the superconducting conductor layer 3C of the third superconducting wire 10C, use the MOD method which is the same method as the connection structure 100 of the superconducting wires. To do.

Next, an opening 13C is formed in the back surface 12C of the base material 1C of the third superconducting wire 10C with a depth reaching the intermediate layer 2C by etching (opening step).
The formation of each opening 13C is performed in the same process as the formation of the opening 13 of the superconducting wire connecting structure 100 described above.
That is, the etching includes a mask formation process and a removal process.

In the mask process, as shown in FIG. 8D, the entire connection portion of the first to third superconducting wires 10A to 10C is covered with an etching resist 51, and exposed according to the formation pattern of the plurality of openings 13C. Then, the resist in the exposed portion is removed to form a mask.
In the removing step, the plurality of openings 13C are formed from the back side of the substrate 1C by dipping in an etching solution according to a mask made of the etching resist 51. Also in this case, the opening 13C is formed up to the intermediate layer 2C.

Next, as shown in FIG. 8E, the etching resist 51 is removed, and an oxygen annealing step of doping oxygen into the superconducting conductor layers 3, 3, and 3C of the first to third superconducting wires 10A to 10C. Is done. The conditions for the oxygen annealing are the same as in the case of the superconducting wire connection structure 100.
Then, the silver stabilization layer is formed by depositing silver on the surface of the connection portion or baking after applying a silver paste, and then forming the copper stabilization layer on the surface by electrolytic plating or the like. A layer forming step is performed. At this time, the stabilization layer may be formed to fill the opening 13C.

Next, the reinforcing wire 10D having the stabilization layer 4D and the base material 1D is attached to the outer surface of the stabilization layer 4 on the back surface 12 side of the base material 1 of the first and second superconducting wires 10A and 10B ( (See FIG. 7).
The stabilizing layer 4D and the substrate 1D of the reinforcing wire 10D are made of the same material as the stabilizing layer 4 and the substrate 1 of the first and second superconducting wires 10A and 10B. The reinforcing wire 10D is made of the stabilizing layer 4D. Is arranged to face the stabilization layer 4 of the first and second superconducting wires 10A and 10B, and the stabilization layers 4 and 4D are joined. For example, when the stabilization layers 4 and 4D are silver stabilization layers, they are joined by Ag-Ag diffusion bonding.
And the connection structure 100 of a superconducting wire is formed by these processes.

[Technical effects of the second embodiment]
In the superconducting wire connecting structure 100C, as with the superconducting wire connecting structure 100, oxygen is supplied to the superconducting conductor layers 3, 3, and 3C through the openings 13 and 13C, thereby effectively promoting oxidation. Become. Therefore, the superconductivity of the superconducting conductor layers 3, 3 and 3C of the first to third superconducting wires 10A to 10C can be kept high, and the time required for oxygen annealing can be shortened.

Also, the opening 13C is formed side by side in the longitudinal direction of each of the superconducting wires 10A to 10C, the opening 13C is formed by etching, the intermediate layer 2 includes a bed layer containing Al ₂ O ₃ , The effect of using the MOD method for joining the superconducting conductor layers 3, 3, 3 C is the same as that of the superconducting wire connecting structure 100.

[Others]
The shape of the openings 13 and 13C in the above embodiments is not limited to a rectangle. The openings 13 and 13C may be formed in other shapes such as a circle. For example, a honeycomb structure having hexagonal openings is preferable because the area of the openings can be increased while suppressing a decrease in strength. Further, the opening may be formed in a groove shape. In that case, the opening can be formed widely, and oxygen can be effectively supplied to each superconducting conductor layer 3 or 3C.

  In each of the above embodiments, the first and second superconducting wires 10A and 10B having the intermediate layer 2 are exemplified. However, the opening 13 can be formed even in the case of a superconducting wire having no intermediate layer 2. . That is, the opening 13 may be formed so as not to penetrate the superconducting conductor layer 3, and the opening 13 may be formed to a depth not penetrating the base material 1 by adjusting the etching solution or adjusting the etching time.

  Further, in each of the above embodiments, the case where the superconducting conductor layer 3 or 3C is joined by the MOD method is exemplified, but the present invention is not limited to this. For example, bonding may be performed by chemical vapor deposition (CVD), laser vapor deposition (PLD), or metal organic chemical vapor deposition (MOCVD).

1,1C, 1D Base material 2,2C Intermediate layer 3,3,3C Superconducting conductor layer (oxide superconducting conductor layer)
4,4D Stabilization layer 10 Superconducting wire 10A First superconducting wire (superconducting wire)
10B Second superconducting wire (superconducting wire)
10C Third superconducting wire (superconducting wire for connection)
10D reinforcing wire 11 Deposition surface (main surface)
12, 12C Back surface 13, 13C Opening 51 Etching resist 60 Reinforcing member 61 One end 62 Other end 100, 100C Superconducting wire connection structure

Claims (11)

A superconducting wire connecting structure in which the connecting end portions of the superconducting wires having the oxide superconducting conductor layer formed on one side of the base material are polymerized and connected,
The oxide superconducting conductor layers of the two superconducting wires are joined face to face,
An opening is provided at a depth not penetrating the oxide superconducting conductor layer on a surface opposite to the oxide superconducting conductor layer in the base material within a bonding range of one or both of the superconducting wires. Characteristic superconducting wire connection structure.   2. The superconducting wire connecting structure according to claim 1, further comprising a reinforcing member having one end and the other end individually connected to the two superconducting wires on both sides of the opening.   3. The reinforcing member is characterized in that one end and the other end of each of the reinforcing members are joined to the opposite side of the base material of the two superconducting wires to the oxide superconducting conductor layer. The superconducting wire connection structure described. An oxide superconducting conductor layer is formed on one side of the substrate, and two superconducting wires facing each other are connected to each other by a connecting superconducting wire in which an oxide superconducting conductor layer is formed on one side of the substrate. A superconducting wire connection structure that is bridge-connected,
The oxide superconducting conductor layer of the two superconducting wires and the oxide superconducting conductor layer of the connecting superconducting wire are joined face to face,
The oxide superconducting conductor on the surface opposite to the oxide superconducting conductor layer in the base material within the joining range of one or both of the two superconducting wires and the connecting superconducting wire. A connection structure for a superconducting wire, characterized in that an opening is provided at a depth that does not penetrate the layer. The superconducting wire comprises an intermediate layer between the base material and the oxide superconducting conductor layer,
The superconducting wire connecting structure according to any one of claims 1 to 4, wherein the opening is formed up to an intermediate layer.   The superconducting wire connecting structure according to any one of claims 1 to 5, wherein the opening is formed in a groove shape.   The superconducting wire connecting structure according to any one of claims 1 to 5, wherein a plurality of the openings are formed side by side. A superconducting wire connecting method in which the connection ends of the superconducting wires formed with an oxide superconducting conductor layer on one side of the base material are polymerized and connected,
An exposing step of exposing the oxide superconducting conductor layer of the two superconducting wires;
A joining step in which the oxide superconducting conductor layers of the two superconducting wires are joined face to face;
An opening that forms an opening at a depth not penetrating the oxide superconducting conductor layer by etching on a surface opposite to the oxide superconducting conductor layer in the base material within a bonding range of one or both of the superconducting wires. Process,
A method of connecting a superconducting wire comprising an oxygen annealing step for the oxide superconducting conductor layer.   The joining step includes a step of disposing a precursor of the oxide superconducting conductor on one or both of the oxide superconducting conductor layers of the two superconducting wires, and a step of firing the precursor of the oxide superconducting conductor; The superconducting wire connecting method according to claim 8, comprising: For connection in which an oxide superconducting conductor layer is formed on one side of a base material in a state in which the connection ends of two superconducting wires having an oxide superconducting conductor layer formed on one side of the base material are butted together A superconducting wire connecting method for bridge connection with a superconducting wire of
An exposing step of exposing the oxide superconducting conductor layer of the two superconducting wires;
A joining step of joining the oxide superconducting conductor layer of the two superconducting wires and the oxide superconducting conductor layer of the superconducting wire for connection facing each other;
Etching is performed on the surface opposite to the oxide superconducting conductor layer in the base material within the bonding range of one or both of the two superconducting wires and the connecting superconducting wires. An opening step of forming an opening at a depth not penetrating the physical superconductor layer;
A method of connecting a superconducting wire comprising an oxygen annealing step for the oxide superconducting conductor layer.   In the joining step, a precursor of the oxide superconducting conductor is disposed on one or both of the oxide superconducting conductor layer of the two superconducting wires and the oxide superconducting conductor layer of the connecting superconducting wire. The method for connecting a superconducting wire according to claim 10, further comprising a step of firing the precursor of the oxide superconducting conductor.

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