JP6274975B2 - Oxide superconducting wire connecting structure manufacturing method and oxide superconducting wire connecting structure - Google Patents

Description

  The present invention relates to a method for manufacturing a connection structure of oxide superconducting wires and a connection structure of oxide superconducting wires.

One of the electric devices that can solve energy problems in recent years is a superconducting device such as a cable, a coil, a motor, and a magnet using an oxide superconductor as a low-loss conductive material. In order to use an oxide superconductor for these devices, the oxide superconductor is generally processed into a wire.
As an oxide superconducting wire, an oxide superconducting layer was laminated on a tape-shaped metal substrate via an intermediate layer, and a protective layer and a stabilizing layer made of a highly conductive metal material were further provided on the superconducting layer. The structure is known.

  Such an oxide superconducting wire is manufactured through many steps due to its multilayer structure, but has not yet been formed as a single oxide superconducting wire with a length required for use in superconducting equipment. . Therefore, there is a demand for a technique for connecting oxide superconducting wires.

As a connecting method of the oxide superconducting wire, a connecting method using solder is known. However, since solder does not have superconducting properties, there is a problem that resistance is generated at the joint.
As a connection method in which a resistance value does not occur at the joint, Patent Document 1 discloses superconductivity by removing the protective layer near the end of the superconducting wire and bringing the exposed superconducting layers into contact with each other and accommodating them in a heating furnace. A technique for melting and diffusing layers is described.

Special table 2011-515792 gazette

  In the technique described in Patent Document 1, since a connection is made using a heating furnace, the layers other than the superconducting layer are easily affected by heating. For example, there is a problem that the function of the superconducting wire may be impaired due to dissolution of the protective layer.

  An object of this invention is to provide the manufacturing method of the connection structure of an oxide superconducting wire which can suppress the resistance of a junction part, without impairing the function of each layer of an oxide superconducting wire.

In order to solve the above-mentioned problems, a method for manufacturing a connection structure of oxide superconducting wires according to the present invention includes a first protective layer comprising an intermediate layer, an oxide superconducting layer, and Ag or an Ag alloy on a tape-like substrate. A step of preparing a second oxide superconducting wire, a step of removing a main protective layer at the tip of the first and second oxide superconducting wires, and forming an exposed portion of the oxide superconducting layer; First, the exposed portions of the second oxide superconducting wire are brought into contact with each other and contacted with each other, and laser light is irradiated from the substrate side of the oxide superconducting wire, thereby locally heating the overlapping portion of the exposed portions. And a diffusion bonding step of diffusion bonding the oxide superconducting layers.
According to this configuration, by connecting the oxide superconducting layers of the oxide superconducting wire to each other by diffusion bonding, it is possible to configure a connection structure in which the normal conducting substance does not intervene in the joint and no resistance of the joint occurs. In addition, since the overlapping portion of the oxide superconducting wire is locally heated by laser light, it is difficult for other layers constituting the oxide superconducting wire to be affected by heat, and deterioration of the other layers can be suppressed.

In the above connection structure manufacturing method, in the diffusion bonding step, a tip surface of the first oxide superconducting wire facing the exposed portion of the main protective layer and a tip of the second oxide superconducting wire A step of forming a sub-protective layer containing Ag or an Ag alloy on the oxide superconducting layer of the first oxide superconducting wire exposed in the gap. Furthermore, you may have.
According to this configuration, the tip of the oxide superconducting wire rides on the main protective layer by overlapping the oxide superconducting wires with a gap between the tip surface of the main protective layer and the tip of the oxide superconducting wire. There is no. Accordingly, the oxide superconducting layers are reliably brought into contact with each other, and diffusion bonding is reliably performed, and the resistance of the joint portion can be suppressed. Further, by forming a sub-protection layer in the gap, the exposed oxide superconducting layer can be covered and protected.

In the above connection structure manufacturing method, in the diffusion bonding step, a tip surface of the second oxide superconducting wire facing the exposed portion of the main protective layer and a tip of the first oxide superconducting wire Bonding may be performed in a state where the two are in contact with each other.
According to this configuration, since the oxide superconducting layer of the second oxide superconducting wire is entirely covered, it is not necessary to form a sub-protective layer for covering and protecting the oxide superconducting layer, and the manufacturing process is reduced. It can be simplified.

In the above connection structure manufacturing method, in the diffusion bonding step, a tip surface of the first oxide superconducting wire facing the exposed portion of the main protective layer and a tip of the second oxide superconducting wire And a front end surface of the second oxide superconducting wire facing the exposed portion of the main protective layer and a front end of the first oxide superconducting wire. Bonding with a second gap in between, and forming a sub-protection layer containing Ag or an Ag alloy on the oxide superconducting layer exposed in the first and second gaps, respectively You may have.
According to this configuration, it is possible to reliably prevent the tip of the oxide superconducting wire from riding on the main protective layer by overlapping the first and second oxide superconducting wires with a gap provided at the tip. . Accordingly, the oxide superconducting layers are reliably brought into contact with each other, and diffusion bonding is reliably performed, and the resistance of the joint portion can be suppressed. Further, by forming a sub-protection layer in the gap, the exposed oxide superconducting layer can be covered and protected.

Moreover, one embodiment of the manufacturing method of the connection structure of an oxide superconducting wire has the 1st and 2nd which has a main protective layer containing an intermediate | middle layer, an oxide superconducting layer, and Ag or an Ag alloy on a tape-shaped base material. And a third oxide superconducting wire having an intermediate layer and an oxide superconducting layer on a tape-like base material and relaying the first and second oxide superconducting wires. Removing the main protective layer at the tip of the first and second oxide superconducting wires to form an exposed portion of the oxide superconducting layer; and the steps of the first and second oxide superconducting wires. The tip surfaces on the side where the exposed part is formed are arranged to face each other, and the oxide superconducting layer of the third oxide superconducting wire is in contact with the oxide superconducting layer of the exposed part facing each other. And the substrate side of the first and second oxide superconducting wires. Or by irradiating a laser beam from the third said substrate side of the oxide superconducting wire has a step of diffusion bonding said oxide superconducting layer between the overlapping, the.
According to this configuration, by connecting the oxide superconducting layers of the oxide superconducting wire to each other by diffusion bonding, it is possible to configure a connection structure in which the normal conducting substance does not intervene in the joint and no resistance of the joint occurs. In addition, since the overlapping portion of the oxide superconducting wire is locally heated by laser light, it is difficult for other layers constituting the oxide superconducting wire to be affected by heat, and deterioration of the other layers can be suppressed. In addition, it is possible to provide a connection structure in which the oxide superconducting wire is not reversed at the connection portion.

In the manufacturing method of the connection structure, the oxidation of the first oxide superconducting wire exposed in a gap between the main protective layer of the first oxide superconducting wire and the third oxide superconducting wire. A superconducting layer, an oxide superconducting layer of the second oxide superconducting wire exposed in a gap between the main protective layer of the second oxide superconducting wire and the third oxide superconducting wire, and On at least one of the oxide superconducting layers of the third oxide superconducting wire exposed between the first oxide superconducting wire and the second oxide superconducting wire, Ag or You may have the process of forming the sub-protection layer containing Ag alloy.
According to this configuration, the exposed oxide superconducting layer can be covered and protected by forming the sub-protective layer in the gap.

Also, the oxide superconducting wire connecting structure according to one embodiment is a connecting structure in which a first and second oxide superconducting wires are formed by laminating an intermediate layer and an oxide superconducting layer on a tape-like base material. The first and second oxide superconducting wires form a joined portion in which the oxide superconducting layers in the vicinity of each other end face each other and are diffusion-bonded to each other, and the longitudinal direction extends from the joined portion. A protective layer containing Ag or an Ag alloy is formed on the oxide superconducting layer of the first and second oxide superconducting wires, and the protective layer of the first oxide superconducting wire is a first film. A thick part and a second film thickness part which is thinner than the first film thickness part and is formed between the first film thickness part and the joint part are included.
According to this configuration, the oxide superconducting layers of the oxide superconducting wire are diffusion-bonded to each other, so that the normal conducting substance does not intervene in the joint, and the resistance of the joint does not occur.
In addition, by forming the second film thickness part thinner than the first film thickness part, the exposed part of the oxide superconducting layer formed when the first and second oxide superconducting wires are overlapped with each other can be obtained. It can be protected by the film thickness. Since the second film thickness portion can be formed in a range and thickness that can cover and protect the exposed portion, the use of Ag can be suppressed and the cost can be reduced.

In addition, the connection structure of the oxide superconducting wire according to one embodiment includes first, second, and third oxide superconducting wires having an intermediate layer and an oxide superconducting layer on a tape-like base material. A connection structure in which the second oxide superconducting wire is connected by relaying with the third oxide superconducting wire, and the tip surfaces of the first and second oxide superconducting wires are arranged to face each other. Each of the oxide superconducting layers of the third oxide superconducting wire forms diffusion joints facing the oxide superconducting layers of the first and second oxide superconducting wires, respectively, A protective layer containing Ag or an Ag alloy is formed on the oxide superconducting layer of the first and second oxide superconducting wires along the longitudinal direction from the joint, and the protective layer includes a first film thickness portion. And thinner than the first film thickness part, and between the first film thickness part and the joint part. And a second film thickness portion was made.
According to this configuration, by connecting the oxide superconducting layers of the oxide superconducting wire to each other by diffusion bonding, it is possible to configure a connection structure in which the normal conducting substance does not intervene in the joint and no resistance of the joint occurs. In addition, it is possible to provide a connection structure in which the oxide superconducting wire is not reversed at the connection portion.

  According to the present invention, the oxide superconducting layers of the oxide superconducting wire are diffusion-bonded to each other, so that no normal conducting substance is interposed in the joint, and the resistance of the joint can be suppressed. In addition, since the overlapping portion of the oxide superconducting wire is locally heated by laser light, it is difficult for other layers constituting the oxide superconducting wire to be affected by heat, and deterioration of the other layers can be suppressed.

It is a perspective view which shows the front-end | tip of the oxide superconducting wire used for a connection structure. It is a cross-sectional schematic diagram which shows 1st Embodiment of a connection structure. It is a schematic diagram which shows the manufacturing method of the connection structure which concerns on this invention, Fig.3 (a) shows the state which accumulated the exposed part of a pair of oxide superconducting wire, FIG.3 (b) is a laser beam. Shows a diffusion bonding step of irradiating It is a cross-sectional schematic diagram which shows the modification 1 of a connection structure. It is a cross-sectional schematic diagram which shows the modification 2 of a connection structure.

  Hereinafter, embodiments of an oxide superconducting wire according to the present invention will be described with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent. In each figure, an XYZ coordinate system is described in which the width direction of the wire is the X direction, the longitudinal direction is the Y direction, and the thickness direction is the Z direction.

(Oxide superconducting wire)
FIG. 1 is a perspective view schematically showing a tip 1a of an oxide superconducting wire 1 according to the present invention. The oxide superconducting wire 1 has a structure in which an intermediate layer 11, an oxide superconducting layer 12, and a main protective layer 13 are laminated in this order on a tape-like base material 10.

As the base material 10, a nickel alloy represented by Hastelloy (trade name, manufactured by Haynes, USA), an oriented Ni—W alloy in which a texture is introduced into a nickel alloy is applied.
What is necessary is just to adjust the thickness of the base material 10 suitably according to the objective, and it can be set as the range of 10-500 micrometers.

The intermediate layer 11 is formed on the base material 10. As an example, the intermediate layer 11 may have a laminated structure of a diffusion prevention layer, an alignment layer, and a cap layer in order from the base material side, but one or both of the diffusion prevention layer and the bed layer may be omitted. .
The diffusion prevention layer is made of Si ₃ N ₄ , Al ₂ O ₃ , GZO (Gd ₂ Zr ₂ O ₇ ), etc., and is formed to a thickness of 10 to 400 nm, for example.
The bed layer is a layer for reducing the interfacial reactivity and obtaining the orientation of the film formed thereon. Y ₂ O ₃ , Er ₂ O ₃ , CeO ₂ , Dy ₂ O _3, Er ₂ O ₃ , Eu ₂ O ₃ , Ho ₂ O ₃ , La ₂ O _3, etc., and the thickness is, for example, 10 to 100 nm.
The orientation layer is formed from a biaxially oriented material in order to control the crystal orientation of the cap layer thereon. As the material of the alignment layer, Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O ₃ , Zr ₂ Examples thereof include metal oxides such as O ₃ , Ho ₂ O ₃ , and Nd ₂ O ₃ . This alignment layer is preferably formed by an IBAD (Ion-Beam-Assisted Deposition) method.
The cap layer is formed on the surface of the above-described alignment layer and is made of a material that allows crystal grains to self-orient in the in-plane direction. Specifically, CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd _{2 O 3, ZrO 2, YSZ,} Ho 2 O 3, Nd 2 O 3, consist of LaMnO ₃ like. The film thickness of the cap layer can be formed in the range of 50 to 5000 nm.

The oxide superconducting layer 12 may be a known oxide superconductor, and specifically, REBa ₂ Cu ₃ O _7-X (RE is a rare earth element, Y, La, Ce, Pr). , Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Examples of the oxide superconducting layer 12 include Y123 (YBa ₂ Cu ₃ O _7-X ) or Gd123 (GdBa ₂ Cu ₃ O _7-X ). In this copper oxide superconductor, the base material is an insulator, but it becomes an oxide superconductor with a well-crystallized structure by incorporating oxygen by the oxygen annealing treatment described in the connection method described later, and has the property of exhibiting superconducting properties. have.
The oxide superconducting layer 12 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

The main protective layer 13 is a layer made of Ag or an Ag alloy formed on the upper surface 12 a of the oxide superconducting layer 12. The main protective layer 13 serves to protect the oxide superconducting layer 12. It also bypasses overcurrent that occurs in the event of an accident. In addition, the chemical reaction occurring between the oxide superconducting layer 12 and the layer provided on the upper surface side of this layer is suppressed, and a part of the elements of one layer penetrates into the other layer side and the composition is broken. It has functions such as preventing the deterioration of superconducting properties due to. The main protective layer 13 can be formed by a film forming method such as a sputtering method at room temperature.
The main protective layer 13 is formed on the upper surface 12a of the oxide superconducting layer 12 with a thickness of 1 μm to 30 μm, for example.
When the main protective layer 13 is formed by the sputtering method, Ag particles wrap around the side surfaces of the base material 10, the intermediate layer 11, and the oxide superconducting layer 12 in addition to the upper surface 12 a of the oxide superconducting layer 12. A thin layer is formed.

The main protective layer 13 is removed near the tip of the oxide superconducting wire 1. Thus, an exposed portion 18 where the upper surface 12a of the oxide superconducting layer 12 is exposed is formed near the tip of the oxide superconducting wire 1. The main protective layer 13 can be removed by etching with an etchant such as a mixed solution of ammonia and hydrogen peroxide or nitric acid.
The exposed portion 18 is formed in a region at a distance H1 from the tip 1a of the oxide superconducting wire 1. That is, the main protective layer 13 is removed in the vicinity of the front end 1a such that the front end surface 13a of the main protective layer 13 remaining without being removed and the front end 1a of the oxide superconducting wire 1 become a distance H1.
In the exposed portion 18, the oxide superconducting layer 12 is diffusion bonded in the connection structure 30 (see FIG. 2) described later to form the bonded portion 4.
The distance H1 can be set to, for example, 5 mm or more and 50 mm or less. Thereby, while joining part 4 of sufficient length is formed, joining part 4 does not become long too much.

Further, the main protective layer 13 may be formed by laminating a metal tape (not shown) via a solder layer on the above-described layer made of Ag or an Ag alloy (Ag layer). In this case, as the metal tape, a relatively inexpensive conductive metal material such as copper, a copper alloy such as a Cu—Zn alloy or a Cu—Ni alloy, aluminum or an alloy thereof, or stainless steel can be used. The thickness of a metal tape can be 10-300 micrometers, for example.
In addition, the main protective layer 13 may be obtained by further laminating a plating coating layer on the above-described layer made of Ag or an Ag alloy (Ag layer). In this case, the plating coating layer may cover not only the Ag layer but also the entire circumference of the wire. Examples of the metal used for the plating coating layer include copper, nickel, gold, silver, chromium, tin and the like, and one or a combination of two or more of these metals can be used. The thickness of the plating coating layer can be 10 μm or more and 100 μm or less.
The laminated metal tape or plating coating layer functions as a bypass for commutating the current of the oxide superconducting layer 12 together with the Ag layer when the oxide superconducting layer 3 attempts to transition from the superconducting state to the normal conducting state. .

(Connection structure)
Next, a pair of oxide superconducting wires having a structure equivalent to that of the oxide superconducting wire 1 described above is prepared, and a connection structure 30 in which these are connected will be described with reference to FIG.
In the following description, one of the pair of oxide superconducting wires is the first oxide superconducting wire 1 and the other is the second oxide superconducting wire 2.
The second oxide superconducting wire 2 has a structure equivalent to that of the first oxide superconducting wire 1, and has a structure in which an intermediate layer 21, an oxide superconducting layer 22, and a main protective layer 23 are sequentially laminated on a base material 20. Have An exposed portion 28 from which the main protective layer 23 has been removed is formed in a region at a distance H2 from the tip 2a of the second oxide superconducting wire 2.

As shown in FIG. 2, the connection structure 30 of the first embodiment is a structure that connects the first oxide superconducting wire 1 and the second oxide superconducting wire 2.
In the first and second oxide superconducting wires 1 and 2, the main protective layers 13 and 23 in the vicinity of the ends 1 a and 2 a are removed to form exposed portions 18 and 28. In the connection structure 30, the exposed portions 18 and 28 are arranged so as to be opposed to each other, and the oxide superconducting layers 12 are diffusion-bonded to form the bonded portion 4.

A first gap 25 is provided between the tip 1 a of the first oxide superconducting wire 1 and the tip surface 23 a of the main protective layer 23 of the second oxide superconducting wire 2. Similarly, a second gap 15 is provided between the tip 2 a of the second oxide superconducting wire 2 and the tip surface 13 a of the main protective layer 13 of the first oxide superconducting wire 1.
As described above, the exposed portions 18 and 28 are formed by removing the main protective layers 13 and 23 by etching. Therefore, the length H1 along the longitudinal direction of the exposed portion 18 of the first oxide superconducting wire 1 and the length H2 along the longitudinal direction of the exposed portion 28 of the second oxide superconducting wire 2 are the same. It is difficult to make the length, and a slight difference in length occurs. By providing the first and second gaps 25 and 15, even when the length H1 and the length H2 are different lengths, the tip of one oxide superconducting wire is on the other main protective layer. I won't get on. Therefore, the exposed portions 18 and 28 of the first and second oxide superconducting wires 1 and 2 are reliably in contact with each other.

  In the connection structure 30, the first sub-protective layer 14 is formed on the surface (+ Z side) where the second oxide superconducting wire 2 is disposed. Similarly, a second sub-protective layer 24 is formed on the surface on which the first oxide superconducting wire 1 is disposed (the surface on the −Z side).

The first sub protective layer 14 is provided to protect the oxide superconducting layer 12 exposed from the second gap 15, and the second sub protective layer 24 is oxidized from the first gap 25. It is provided to protect the physical superconducting layer 22.
The first sub-protection layer 14 includes a gap 14 a formed on the oxide superconducting layer 12 in the second gap 15 and the main protective layer 13 of the first oxide superconducting wire 1 in the vicinity of the joint 4. It has the surface part 14b formed on top, and the back surface part 14c formed on the base material 20 of the 2nd oxide superconducting wire 2. FIG. The front surface portion 14b and the back surface portion 14c are portions that are inevitably formed when the gap portion 14a is formed.
Similarly, the second sub protective layer 24 includes a gap portion 24a formed in the first gap 25, and a surface portion 24b formed on the main protective layer 23 of the second oxide superconducting wire 2. And a back surface portion 24c formed on the base material 10 of the first oxide superconducting wire 1.

  The first and second sub protective layers 14 and 24 are layers made of Ag or an Ag alloy. Therefore, when the main protective layers 13 and 23 are composed only of a layer (Ag layer) made of Ag or an Ag alloy, the surface portion 14 b of the first sub protective layer 14 formed on the main protective layer 13. Is integrated with the main protective layer 13 to eliminate its boundary. Similarly, the surface portion 24b of the second sub protective layer 24 formed on the main protective layer 23 is integrated with the main protective layer 23 and the boundary thereof is eliminated.

The first and second sub-protective layers 14 and 24 serve to protect the exposed portions 18 and 28 of the oxide superconducting layers 12 and 22. The first and second sub protective layers 14 and 24 can be formed by a film forming method such as a sputtering method at room temperature.
By forming the first and second sub-protective layers 14 and 24 by sputtering, Ag particles have also entered the surfaces of the tips 1a and 2a of the first and second oxide superconducting wires 1 and 2, respectively. A thin layer of Ag is formed.

The first sub protective layer 14 is integrated with the main protective layer 13 to form a protective layer 31. The second sub protective layer 24 is integrated with the main protective layer 23 to form a protective layer 32.
The protective layer 31 is formed along the longitudinal direction from the joint 4 on the oxide superconducting layer 12 of the first oxide superconducting wire 1. The protective layer 31 is located between the first film thickness portion 16 constituted by the main protective layer 13 and the surface portion 14 b of the first sub protective layer 14, and between the first film thickness portion 16 and the bonding portion 4. And the second film thickness portion 17 composed only of the gap portion 14 a of the first sub-protective layer 14. The first film thickness portion 16 is formed thicker than the second film thickness portion 17 by the thickness of the main protective layer 13.
When the main protective layer 13 is a layer in which a metal tape is laminated on the Ag layer via a solder layer, the first film thickness portion 16 includes the Ag layer and the solder in order from the oxide superconducting layer 12 side. A layer, a metal tape, and a first sub protective layer 14 are sequentially laminated. Further, when the main protective layer 13 is a layer in which a plating coating layer is laminated on the Ag layer, the first film thickness portion 16 includes the Ag layer, the plating coating layer, the first coating layer in order from the oxide superconducting layer 12 side. One sub-protective layer 14 is sequentially laminated.

Similarly, the protective layer 32 is formed along the longitudinal direction from the joint 4 on the oxide superconducting layer 22 of the second oxide superconducting wire 2. The protective layer 32 is located between the first film thickness portion 26 composed of the main protective layer 23 and the surface portion 24 b of the second sub protective layer 24, and between the first film thickness portion 26 and the bonding portion 4. And the second film thickness portion 27 composed only of the gap portion 24a of the second sub-protective layer 24.
In the case where the main protective layer 23 is a layer in which a metal tape is laminated on the Ag layer via a solder layer, the first film thickness portion 26 includes an Ag layer, a solder layer, The metal tape and the second sub protective layer 24 are sequentially laminated. Further, when the main protective layer 23 is a layer in which a plating coating layer is laminated on the Ag layer, the first film thickness portion 26 is formed in order from the oxide superconducting layer 22 side by Ag layer, plating coating layer, Two sub-protective layers 24 are sequentially stacked.

(Connection method for oxide superconducting wire)
Next, a connection method for connecting the first and second oxide superconducting wires 1 and 2 to form the connection structure 30 will be described.

  First, a first oxide superconducting wire 1 and a second oxide superconducting wire 2 are prepared. At this time, the main protective layers 13 and 23 in the vicinity of the tips 1a and 2a of the first and second oxide superconducting wires 1 and 2 are removed with an etching solution.

  Next, as shown in FIG. 3A, the exposed portion 18 of the first oxide superconducting wire 1 and the exposed portion 28 of the second oxide superconducting wire 2 are overlapped to form an overlapping portion 3. . Between the front ends 1a, 2a of the first and second oxide superconducting wires 1 and 2 and the front end surfaces 13a, 23a of the main protective layers 13, 23 on both sides of the overlapping portion 3, the first and second The gaps 25 and 15 are formed. In this state, the oxide superconducting layers 12 and 22 are brought into contact with each other between the surfaces.

The first and second oxide superconducting wires 1 and 2 may be fixed in a state where the overlapping portion 3 is pressurized. In this case, the overlapping portions 3 are sandwiched by a vise (vise) or the like from the thickness direction to pressurize the exposed portions 18 and 28 to 30 MPa. When pressurization is performed at a pressure exceeding 30 MPa, the oxide superconducting layers 12 and 22 may be cracked in the crystal structure to deteriorate the superconducting characteristics.
As described above, in the case where the laser beam irradiation at the subsequent stage is performed while pressing the overlapping portion 3 with a vice, the member that holds the base material 20 side of the second oxide superconducting wire 2 is irradiated with the laser beam. Therefore, it is preferable to use a thin plate having high heat conductivity as the member or a member made of a member that transmits laser light.

Next, as shown in FIG. 3B, the overlapping portion 3 is irradiated with laser light L from the base material 20 side of the second oxide superconducting wire 2. Thereby, the oxide superconducting layers 12 and 22 in the overlapping portion 3 are heated, and the oxide superconducting layers 12 and 22 are diffusion bonded (diffusion bonding process).
The RE-123-based oxide superconductor constituting the oxide superconducting layers 12 and 22 has a stable layer up to the vicinity of the melting point, but tends to decompose when the melting point is exceeded. Therefore, it is preferable to heat the laser light L so that the oxide superconducting layers 12 and 22 in the overlapping portion 3 have a temperature equal to or lower than the melting point and close to the melting point. Thereby, the oxide superconducting layers 12 and 22 in the overlapping portion 3 are diffusion-bonded. Although the melting point temperature of the oxide superconductor differs depending on the constituent materials, for example, when the melting point temperature of the superconducting conductor is about 980 ° C., the oxide superconductor is heated to around 900 ° C.

  The laser light L preferably uses a wavelength of 750 nm or more (infrared laser). By setting the wavelength to 750 nm or more, the laser light L can directly heat the oxide superconducting layers 12 and 22 in the overlapping portion 3 because the heat penetrates into the inside without heating only the surface of the substrate 20. Thereby, the oxide superconducting layers 12 and 22 can be efficiently heated.

The laser light L preferably has a power density of less than 5 × 10 ⁶ W / m ² in the spot S. When the substrate 20 is irradiated with the laser beam L having a power density of 5 × 10 ⁶ W / m ² or more, the temperature of the overlapping portion 3 is instantaneously increased, and the oxide superconducting layers 12 and 22 are melted to form diffusion bonding. May not be done.

  In this embodiment, laser light is irradiated only from the base material 20 side of the second oxide superconducting wire 2, but at the same time, laser light is also emitted from the base material 10 side of the first oxide superconducting wire 1. It may be irradiated.

  Next, the first sub-protective layer 14 is formed by sputtering from the side where the second oxide superconducting wire 2 is disposed. Similarly, the second sub-protective layer 24 is formed by sputtering from the side where the first oxide superconducting wire 1 is disposed. Thereby, the connection structure 30 shown in FIG. 2 is formed.

A second gap 15 is provided between the tip 2 a of the second oxide superconducting wire 2 and the tip surface 13 a of the main protective layer 13. In the second gap 15, the oxide superconducting layer 12 of the first oxide superconducting wire 1 is exposed. By forming the first sub protective layer 14, the exposed oxide superconducting layer 12 can be covered and protected. Similarly, the second sub protective layer 24 covers and protects the exposed portion 28 of the oxide superconducting layer 22 in the first gap 25.
The first and second sub-protection layers 14 and 24 are for protecting the oxide superconducting layers 12 and 22 exposed in the first and second gaps 25 and 15, and therefore only in the vicinity of the junction 4. It is sufficient to form a film.

Next, an oxygen annealing process is performed on the connection structure 30 configured as described above.
The oxygen annealing treatment is performed by heating the connection structure 30 including the first and second oxide superconducting wires 1 and 2 to 300 ° C. to 500 ° C. in an oxygen atmosphere. By this annealing treatment, oxygen can be supplied to the oxide superconducting layers 12 and 22 in the vicinity of the connection structure 30 to adjust the crystal structure, thereby improving the superconducting characteristics.

The oxygen annealing treatment is preferably performed after the first and second sub protective layers 14 and 24 are formed, but may be performed before the first and second sub protective layers 14 and 24 are formed. In this case, there is a possibility that oxygen supplied by the oxygen annealing process may be lost due to heat generated in the process of forming the first and second sub-protective layers 14 and 24. Therefore, heating is suppressed and oxygen escape is prevented by controlling a film thickness to be formed.
Through the above steps, the connection structure 30 can be formed.

  The connection structure 30 is formed by joining the oxide superconducting layers 12 and 22 of the first and second oxide superconducting wires 1 and 2 by diffusion bonding. Therefore, the normal conducting substance is not interposed in the joint 4 and the resistance of the joint 4 can be suppressed.

  Further, in the method for manufacturing the connection structure 30, the overlapping portion 3 of the first and second oxide superconducting wires 1 and 2 is locally heated by the laser beam L, so that the oxide superconducting layers 12 and 22 are diffusion-bonded together. I am letting. The local heating by the laser beam L makes it difficult for the other layers constituting the first and second oxide superconducting wires 1 and 2 to be affected by heat, and the deterioration of the other layers can be suppressed.

In the method for manufacturing the connection structure 30, the first gap 25 is provided between the tip 1 a of the first oxide superconducting wire 1 and the tip surface 23 a of the main protective layer 23 of the second oxide superconducting wire 2. Thus, the tip 1a of the first oxide superconducting wire 1 does not run on the main protective layer 23. Similarly, the second gap 15 is also provided between the tip 2 a of the second oxide superconducting wire 2 and the main protective layer 13, so that the tip 2 a does not run on the main protective layer 13. Therefore, the oxide superconducting layers 12 and 22 are reliably brought into contact with each other, and diffusion bonding is reliably performed. Thereby, the resistance of the junction part 4 can be suppressed.
In addition, since the connection structure 30 includes the oxide superconducting layers 12 and 22 exposed in the first and second gaps 25 and 15, the first and second sub-protective layers 14 and 24 are formed. The superconducting layers 12 and 22 can be protected.

  Furthermore, in the manufacturing method of the connection structure 30, in order to perform the oxygen annealing process after the diffusion bonding process, oxygen is supplied to the oxide superconducting layers 12 and 22 in the vicinity of the bonding portion 4 to adjust the crystal structure. Can do. As a result, the superconducting characteristics in the vicinity of the joint 4 can be improved.

<Modification 1>
In the connection structure 30 of the first embodiment described above, the first gap 25 is provided at the tip of the tip 1a of the first oxide superconducting wire 1, and the tip of the tip 2a of the second oxide superconducting wire 2 is provided. A second gap 15 is provided. However, these may be configured such that a gap is provided in only one of them.
As such an example, a connection structure 40 of Modification 1 will be described with reference to FIG.

The connection structure 40 includes a first oxide superconducting wire 5 and a second oxide superconducting wire 6. The first and second oxide superconducting wires 5 and 6 have a structure equivalent to that of the oxide superconducting wire 1 (see FIG. 1).
That is, the first oxide superconducting wire 5 has a structure in which an intermediate layer 51, an oxide superconducting layer 52, and a main protective layer 53 are sequentially laminated on a base material 50. An exposed portion 58 from which the main protective layer 53 has been removed is formed in a region at a distance H5 from the tip 5a of the first oxide superconducting wire 5.
Similarly, the second oxide superconducting wire 6 has a structure in which an intermediate layer 61, an oxide superconducting layer 62, and a main protective layer 63 are sequentially laminated on a base material 60. Further, an exposed portion 68 from which the main protective layer 63 is removed is formed in a region at a distance H6 from the tip 6a of the second oxide superconducting wire 6.
In the present embodiment, the length H5 along the longitudinal direction of the exposed portion 58 of the first oxide superconducting wire 5 is longer than the length H6 along the longitudinal direction of the exposed portion 68 of the second oxide superconducting wire 6. long.

In this connection structure 40, the exposed portions 58 and 68 are overlapped so that the tip 5 a of the first oxide superconducting wire 5 is in contact with the tip surface 63 a of the main protective layer 63. A gap 55 is provided between the tip 6 a of the second oxide superconducting wire 6 and the tip surface 53 a of the main protective layer 53 of the first oxide superconducting wire 5.
The length H5 along the longitudinal direction of the exposed portion 58 of the first oxide superconducting wire 5 and the length H6 along the longitudinal direction of the exposed portion 68 of the second oxide superconducting wire 6 are the same length. It is difficult to do. In the present embodiment, the length H5 of the exposed portion 58 of the first oxide superconducting wire 5 is longer than the length H6 of the exposed portion 68 of the second oxide superconducting wire 6. Further, the front ends 5a and 6a of the first and second oxide superconducting wires 5 and 6 are in contact with the main protective layer by bringing the entire exposed portion 68 formed short into contact with the opposing exposed portion 58. It prevents the ride on 53 and 63. Therefore, the exposed portions 58 and 68 of the first and second oxide superconducting wires 5 and 6 can reliably come into contact with each other.

In the connection structure 40, a sub-protection layer 54 is formed on the surface (+ Z side) on which the second oxide superconducting wire 6 is disposed. On the other hand, the sub-protective layer is not formed on the surface (the surface on the −Z side) on which the first oxide superconducting wire 5 is disposed.
The sub protective layer 54 includes a gap 54 a formed in the gap 55, a surface 54 b formed on the main protective layer 53 of the first oxide superconducting wire 5, and the second oxide superconducting wire 6. The back surface portion 54c is formed on the base material 60.

The sub protective layer 54 is integrated with the main protective layer 53 to form the protective layer 33.
The protective layer 33 is formed along the longitudinal direction from the joint 44 on the oxide superconducting layer 52 of the first oxide superconducting wire 5. The protective layer 33 includes a first film thickness portion 56 composed of the main protective layer 53 and the surface portion 54 b of the sub protective layer 54, and the first film thickness portion 56 and the bond portion 44 in the vicinity of the bond portion 44. It has a second film thickness portion 57 that is located only between the gap portions 54 a of the sub-protection layer 54.

The connection structure 40 of the first modification can obtain the same effects as the connection structure 30 of the first embodiment.
In addition, the connection structure 40 is not exposed because the exposed portion 68 of the second oxide superconducting wire 6 is covered and exposed by the opposing exposed portion 58, so that the connection structure 40 is on the side where the first oxide superconducting wire 5 is disposed. There is no need to form a secondary protective layer. Therefore, the manufacturing process can be simplified.

<Modification 2>
Next, the connection structure 100 of the modification 2 is demonstrated based on FIG.
The connection structure 100 includes a first oxide superconducting wire 7, a second oxide superconducting wire 8, and a third oxide superconducting wire 9 having a structure equivalent to that of the oxide superconducting wire 1 (see FIG. 1). And it has the structure which connected these.

  The first oxide superconducting wire 7 has an intermediate layer 71, an oxide superconducting layer 72, and a main protective layer 73 on a base material 70, and an exposed portion 78 from which the main protective layer 73 has been removed is provided near the tip 7a. Is formed. The second oxide superconducting wire 8 has an intermediate layer 81, an oxide superconducting layer 82, and a main protective layer 83 on a base material 80, and an exposed portion 88 from which the main protective layer 83 has been removed is located near the tip 8a. Is formed. The third oxide superconducting wire 9 has an intermediate layer 91, an oxide superconducting layer 92, and a main protective layer 93 on a base material 90, and the main protective layer 93 is removed in the vicinity of both ends 9a and 9b. Exposed portions 98 are respectively formed. The third oxide superconducting wire 9 is formed in a short length.

The connection structure 100 has a configuration in which the first oxide superconducting wire 7 and the second oxide superconducting wire 8 are connected via the third oxide superconducting wire 9.
In the connection structure 100, the first oxide superconducting wire 7 and the second oxide superconducting wire 8 are disposed with their tips 7a and 8a adjacent to each other with a predetermined gap 101 therebetween. Note that the stacking directions of the first and second oxide superconducting wires 7 and 8 are the same.
The third oxide superconducting wire 9 is disposed so as to straddle the tips 7a, 8a of the first and second oxide superconducting wires 7, 8. In addition, the exposed portion 98 of the third oxide superconducting wire 9 is opposed to the exposed portions 78 and 88 of the first and second oxide superconducting wires 7 and 8 by diffusion bonding. Forming.

A gap 105 is provided at the tip of each of the tips 7a, 8a, 9a, 9b of the first, second, and third oxide superconducting wires 7, 8, 9.
A first sub-protective layer 102 is formed on the surface (+ Z side) on which the third oxide superconducting wire 9 is disposed. A second sub-protective layer 103 is formed on the surface on which the first and second oxide superconducting wires 7 and 8 are disposed (the surface on the −Z side). Thereby, the exposed portions 78, 88, 98 in the gap 105 are covered and protected.

  The connection structure 100 can be described as a structure in which the connection structures 30 of the first embodiment described above are continuously arranged. With such a structure, not only the various effects of the first embodiment can be obtained, but also a connection structure in which the front and back of the oxide superconducting wire are not reversed at the connection portion can be provided.

In addition, the third oxide superconducting wire 9 may not have the main protective layer 93. In this case, one first superconducting wire 7, 8 between the tips 7 a, 8 a and on the oxide superconducting layer 92 of the third oxide superconducting wire 9 is one first. Two sub-protective layers 103 are disposed. Thereby, the oxide superconducting layer 92 is protected without being exposed.
Further, the tips 7a and 8a of the first and second oxide superconducting wires 7 and 8 may be arranged so as to abut each other (in contact with each other). In this case, the third oxide superconducting wire 9 Since the oxide superconducting layer 92 is not exposed, the second sub protective layer 103 may not be formed.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.
(Sample preparation)
First, the surface of a tape-shaped base material having a width of 10 mm, a thickness of 0.1 mm, and a length of 5000 mm made of Hastelloy C-276 (trade name of Haynes, USA) was polished using alumina having an average particle diameter of 3 μm. Next, the surface of the substrate was degreased and washed with acetone.
An Al ₂ O ₃ (diffusion prevention layer; film thickness: 100 nm) film is formed on the main surface of the substrate by ion beam sputtering, and Y ₂ O ₃ (bed layer; film thickness) is formed thereon by ion beam sputtering. 30 nm) was formed.
Next, MgO (metal oxide layer; film thickness: 5 to 10 nm) is formed on the bed layer by ion beam assisted vapor deposition (IBAD method), and 500 nm thick is formed thereon by pulsed laser vapor deposition (PLD method). CeO ₂ (cap layer) was formed. Next, a 2.0 μm thick GdBa ₂ Cu ₃ O _7-x (oxide superconducting layer) was formed on the CeO ₂ layer by the PLD method.
Next, an Ag layer (main protective layer) having a thickness of 2 μm was formed on the oxide superconducting layer by DC sputtering.
Subsequently, oxygen annealing treatment was performed at 500 ° C. for 10 hours, and the furnace was taken out after cooling for 26 hours.
Next, this sample was cut with a laser beam to obtain a wire having a width of 3 mm.
The oxide superconducting wire of Sample A produced in this way was cooled with liquid nitrogen, and the critical current value was measured and found to be 150A.
The oxide superconducting wire of Sample A is commonly used in the following sample preparation.

"Example 1, comparative example 1"
A manufacturing method of Example 1 and Comparative Example 1 constituting the connection structure shown in FIG. 2 will be described.
A plurality of oxide superconducting wires of Sample A were prepared, and the main protective layer near the end was etched using a mixed solution of ammonia and hydrogen peroxide to form an exposed portion. In addition, the length (H1, H2 in FIG. 2) along the longitudinal direction of the exposed part was 20 mm. Next, the exposed portions of the oxide superconducting wire were overlapped by 15 mm and irradiated with laser light from one side of the substrate to diffuse and bond the oxide superconducting layer (diffusion bonding step).
A 1 μm thick Ag layer (sub-protective layer) was formed by sputtering from the side where each oxide superconducting wire of this sample was placed. Further, oxygen annealing treatment was performed at 500 ° C. for 10 hours, and the furnace was taken out after cooling for 26 hours.
In the diffusion bonding step, the sample of Example 1 is a laser beam having a wavelength of 1064 nm, a power density of 3 × 10 ⁵ W / cm ² and an irradiation time of 10 seconds.
Further, in the diffusion bonding step, a laser beam having a wavelength of 1064 nm, a power density of 5 × 10 ⁶ W / cm ² and an irradiation time of 1 second is used as a sample of Comparative Example 1.

"Example 2"
A manufacturing method of Example 2 that constitutes the connection structure shown in FIG. 4 will be described.
A pair of oxide superconducting wires of Sample A was prepared, and these were used as the first oxide superconducting wire and the second oxide superconducting wire. The main protective layer in the vicinity of each end portion was etched using a mixed solution of ammonia and hydrogen peroxide to form an exposed portion. The length (H5 in FIG. 4) along the longitudinal direction of the exposed portion of the first oxide superconducting wire was 20 mm. The length (H6 in FIG. 4) along the longitudinal direction of the exposed portion of the second oxide superconducting wire was 15 mm.
Next, the exposed portions were overlapped with each other, and laser light was irradiated from one side of the substrate to diffuse and bond the oxide superconducting layer. At this time, as shown in FIG. 4, each wire was arranged so as to cover the entire exposed portion of the second oxide superconducting wire with the exposed portion of the first oxide superconducting wire. Further, the laser beam was set to a wavelength of 1064 nm, a power density of 3 × 10 ⁵ W / cm ² , and an irradiation time of 10 seconds.
A 1 μm Ag layer (sub-protective layer) was formed by sputtering from the side of the sample on which the second oxide superconducting wire is disposed. Further, oxygen annealing treatment was performed at 500 ° C. for 10 hours, and the furnace was taken out after cooling for 26 hours. This is Example 2.

“Comparative Example 2”
A manufacturing method of Comparative Example 2 in which the connection structure is configured by solder bonding will be described.
A pair of the oxide superconducting wires of sample A was prepared, subjected to oxygen annealing treatment at 500 ° C. for 10 hours, and taken out after 26 hours of furnace cooling.
Next, a copper tape was joined to the main protective layer of these wires with solder. Furthermore, the copper tapes outside the body were connected via solder. As the solder, Sn-Pb solder was used. This is referred to as Comparative Example 2.

(Evaluation method and results)
For the connection structures of Examples 1 and 2 and Comparative Examples 1 and 2, the connection resistance and the critical current value were measured. The connection resistance and the critical current value were measured by flowing a current through each connection sample in liquid nitrogen.
Table 1 summarizes the connection resistance of each sample and the critical current value before and after connection.

According to Table 1, in the connection structures of Examples 1 and 2, the critical current value did not change before and after connection, and the connection resistance was less than 1.0 nΩ which can be measured.
On the other hand, the sample of Comparative Example 1 did not have superconducting properties after connection, and no current flowed. When the bonded portion was observed, it was observed that the oxide superconducting layer was dissolved. From this, it is considered that the oxide superconducting conductor was thermally decomposed by heating by laser light irradiation.
In the sample of Comparative Example 2, the critical current value did not change before and after connection. However, the connection resistance was 10 nΩ, which was larger than those in Examples 1 and 2.
From these results, the superiority of the connection structures of Examples 1 and 2 was confirmed.

  Although various embodiments of the present invention have been described above, each configuration in each embodiment and combinations thereof are examples, and addition, omission, replacement, and configuration of configurations are within the scope not departing from the spirit of the present invention. And other changes are possible. Further, the present invention is not limited by the embodiment.

DESCRIPTION OF SYMBOLS 1, 5, 7 ... Oxide superconducting wire (1st oxide superconducting wire), 1a, 2a, 5a, 6a, 7a, 8a, 9a, 9b ... tip 2, 6, 8 ... 2nd oxide superconductivity Wire, 2a ... tip, 3 ... overlapped portion, 4, 44, 104 ... junction, 9 ... third oxide superconducting wire, 10, 20, 50, 60, 70, 80, 90 ... substrate, 11, 21 , 51, 61, 71, 81, 91 ... intermediate layer, 12, 22, 52, 62, 72, 82, 92 ... oxide superconducting layer, 13, 23, 53, 63, 73, 83, 93 ... main protective layer , 13a, 23a, 53a, 63a ... tip surface, 14, 24, 54, 102, 103 ... sub protective layer, 15, 25, 55, 105 ... gap, 18, 28, 58, 68, 78, 88, 98 ... Exposed part, 30, 40, 100 ... connection structure, 31, 32, 33 ... protective layer, H1, H , H5, H6 ... distance, L ... laser light, S ... spot

Claims (6)

Preparing a first and a second oxide superconducting wire having an intermediate layer, an oxide superconducting layer, and a main protective layer containing Ag or an Ag alloy on a tape-shaped substrate;
Removing the main protective layer at the tip of the first and second oxide superconducting wires to form an exposed portion of the oxide superconducting layer;
By exposing the exposed portions of the first and second oxide superconducting wires to face each other and contacting each other, and irradiating laser light from the base material side of the oxide superconducting wire, the overlapping portions of the exposed portions are formed. possess diffusion and bonding step of local heating and diffusion bonding said oxide superconducting layers to each other, and
In the diffusion bonding step, the first oxide superconducting wire is bonded with a gap between a front end surface of the main protective layer facing the exposed portion and a front end of the second oxide superconducting wire. And
Manufacturing of oxide superconducting wire connection structure , further comprising forming a sub-protective layer containing Ag or an Ag alloy on the oxide superconducting layer of the first oxide superconducting wire exposed in the gap Method. In the diffusion bonding step, bonding is performed in a state in which a tip surface of the second oxide superconducting wire facing the exposed portion of the main protective layer is in contact with a tip of the first oxide superconducting wire. The manufacturing method of the connection structure of the oxide superconducting wire of Claim 1 to perform. Preparing a first and a second oxide superconducting wire having an intermediate layer, an oxide superconducting layer, and a main protective layer containing Ag or an Ag alloy on a tape-shaped substrate;
Removing the main protective layer at the tip of the first and second oxide superconducting wires to form an exposed portion of the oxide superconducting layer;
By exposing the exposed portions of the first and second oxide superconducting wires to face each other and contacting each other, and irradiating laser light from the base material side of the oxide superconducting wire, the overlapping portions of the exposed portions are formed. A diffusion bonding step of locally heating and diffusion bonding the oxide superconducting layers,
In the diffusion bonding step, a first gap is provided between a front end surface of the first oxide superconducting wire facing the exposed portion of the main protective layer and a front end of the second oxide superconducting wire. And in a state having a second gap between the tip surface of the second oxide superconducting wire facing the exposed portion of the main protective layer and the tip of the first oxide superconducting wire. Do the joining
Wherein the first and the oxide superconducting layer exposed to the second gap, further comprising, a manufacturing method of the connection structure of the oxides superconducting wire a step of forming a secondary protective layer containing Ag or Ag alloy, respectively. First and second oxide superconducting wires having an intermediate layer, an oxide superconducting layer, and a main protective layer containing Ag or an Ag alloy on a tape-shaped substrate, and an intermediate layer and an oxide on the tape-shaped substrate Preparing a third oxide superconducting wire having a superconducting layer and relaying the first and second oxide superconducting wires;
Removing the main protective layer at the tip of the first and second oxide superconducting wires to form an exposed portion of the oxide superconducting layer;
The tip surfaces of the first and second oxide superconducting wires on which the exposed portions are formed are arranged to face each other, and the oxide superconducting layer of the third oxide superconducting wire is disposed on the exposed portions. A step of contacting the oxide superconducting layer to face each other, and
By irradiating laser light from the substrate side of the first and second oxide superconducting wires or the substrate side of the third oxide superconducting wire, the overlapping oxide superconducting layers are diffused. possess a step of bonding, a,
The oxide superconducting layer of the first oxide superconducting wire exposed in the gap between the main protective layer of the first oxide superconducting wire and the third oxide superconducting wire, the second oxide The oxide superconducting layer of the second oxide superconducting wire exposed in the gap between the main protective layer of the superconducting wire and the third oxide superconducting wire, and the first oxide superconducting wire and the first A sub-protective layer containing Ag or an Ag alloy is formed on at least one of the oxide superconducting layers of the third oxide superconducting wire exposed between the two oxide superconducting wires. A method for producing a connection structure of oxide superconducting wires , comprising a step . A connection structure in which the first and second oxide superconducting wires are formed by laminating an intermediate layer and an oxide superconducting layer on a tape-shaped substrate,
The first and second oxide superconducting wires form a bonded portion in which the oxide superconducting layers near each other end face each other and are diffusion bonded,
A protective layer containing Ag or an Ag alloy is formed on the oxide superconducting layer of the first and second oxide superconducting wires along the longitudinal direction from the joint.
Either the first or second oxide superconducting wire, or both of the protective layers are thinner than the first film thickness portion and the first film thickness portion, and the first film thickness portion and the junction. The oxide superconducting wire connection structure including a second film thickness portion formed between the two portions. The tape-shaped base material comprises first, second, and third oxide superconducting wires having an intermediate layer and an oxide superconducting layer, and the first and second oxide superconducting wires are replaced with a third oxide superconducting wire. A connection structure relayed and connected at
The tip surfaces of the first and second oxide superconducting wires are arranged facing each other,
The oxide superconducting layer of the third oxide superconducting wire forms a bonding part that is diffusion-bonded facing the oxide superconducting layer of the first and second oxide superconducting wires, respectively.
A protective layer containing Ag or an Ag alloy is formed on the oxide superconducting layer of the first and second oxide superconducting wires along the longitudinal direction from the joint.
The protective layer includes a first film thickness portion and a second film thickness portion that is thinner than the first film thickness portion and is formed between the first film thickness portion and the junction portion. Wire connection structure.

Images