WO2020138035A1

WO2020138035A1 - Oxide superconducting wire material and method for manufacturing same

Info

Publication number: WO2020138035A1
Application number: PCT/JP2019/050519
Authority: WO
Inventors: 智羽生
Original assignee: 株式会社フジクラ
Priority date: 2018-12-26
Filing date: 2019-12-24
Publication date: 2020-07-02
Also published as: JP6724125B2; JP2020107445A

Abstract

A superconducting wire material having an oxide superconducting layer that includes a rare earth element, wherein the oxide superconducting layer has a degree of orientation Δφ of 6.0° or less in a plane parallel to the thickness direction, and the superconducting wire material is provided with: a first metal layer that is an Ag layer or a layer containing Ag, and is laminated on a first surface in the thickness direction of the oxide superconducting layer; a second metal layer that is an Ag layer or a layer containing Ag, and is laminated on a second surface on the opposite side from the first surface; and a Cu layer or a layer containing Cu that contacts the first metal layer or the second metal layer in the thickness direction of the oxide superconducting layer.

Description

Oxide superconducting wire and method for producing the same

The present invention relates to an oxide superconducting wire and a method for manufacturing the same.
The present application claims priority to Japanese Patent Application No. 2018-243592 filed in Japan on December 26, 2018, and the content thereof is incorporated herein.

Superconducting wire has low current loss, so it is used as a power supply cable, magnetic coil, etc. Patent Document 1 describes a superconducting wire in which an intermediate layer and an oxide superconducting layer are formed on a substrate having a metal base material, and a copper electrolytic plating film is formed as a stabilizing layer around the substrate.

Japanese Patent No. 5634166

When applying superconducting wires as cables, coils, etc., many superconducting wires are used in a state in which a large number of superconducting wires are integrated in the cross-sectional direction, such as arranging a number of superconducting wires in parallel or winding a plurality of superconducting wires. However, in order to form the oxide superconducting layer having excellent crystal orientation, it is necessary to prepare a thick metal substrate and stack the intermediate layer and the oxide superconducting layer on the basis of the metal substrate. Therefore, there is a problem that the cross-sectional area of the entire superconducting wire including the metal substrate is larger than the cross-sectional area of the oxide superconducting layer.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an oxide superconducting wire having excellent properties per unit cross-sectional area and a method for manufacturing the same.

A first aspect of the present invention is a superconducting wire having an oxide superconducting layer containing a rare earth element, wherein the oxide superconducting layer has an orientation degree Δφ in a plane parallel to a thickness direction of 6.0° or less. The superconducting wire is laminated on the first surface of the oxide superconducting layer in the thickness direction, and is a Ag layer or a first metal layer that is a layer containing Ag, and a second surface opposite to the first surface. And a second metal layer that is an Ag layer or a layer containing Ag and is in contact with the first metal layer or the second metal layer in the thickness direction of the oxide superconducting layer and contains a Cu layer or Cu. And a metal layer.

The metal layer may include a first Cu metal layer in contact with the first metal layer and a second Cu metal layer in contact with the second metal layer.
The first surface in the width direction of the oxide superconducting layer may be covered with the first metal layer, and the second surface may be covered with the second metal layer.
The total thickness of the superconducting wire in the thickness direction of the oxide superconducting layer may be 50 μm or less.

A second aspect of the present invention is a method for producing a superconducting wire having an oxide superconducting layer containing a rare earth element, a step of laminating the oxide superconducting layer on a substrate, and a thickness of the oxide superconducting layer. A step of stacking a first metal layer on the oxide superconducting layer on the side opposite to the substrate in the direction, a step of removing the substrate, and a step of removing the substrate in the thickness direction of the oxide superconducting layer. Laminating a second metal layer on the oxide superconducting layer on the exposed side.

The first metal layer and the second metal layer may be Ag layers or layers containing Ag.
In the thickness direction of the oxide superconducting layer, a Cu layer or a metal layer containing Cu may be laminated so as to be in contact with the first metal layer or the second metal layer.

According to the above aspect of the present invention, since the metal layer having the Ag layer or the layer containing Ag is laminated in contact with both surfaces in the thickness direction of the oxide superconducting layer having crystal orientation, the conventional superconducting wire is It is possible to provide a superconducting wire having excellent characteristics per unit cross-sectional area, as compared with the substrate used for film formation remaining on one side in the thickness direction of the oxide superconducting layer.

It is sectional drawing which shows the superconducting wire of 1st Embodiment. It is sectional drawing which shows the superconducting wire of 2nd Embodiment. It is sectional drawing which shows the superconducting wire of 3rd Embodiment. It is sectional drawing which shows the superconducting wire of 4th Embodiment. It is sectional drawing which shows an example of the superconducting wire which has a board|substrate. It is sectional drawing of the example which removed the side surface part from the superconducting wire which has a board|substrate. It is sectional drawing of the example which removed the board|substrate from the superconducting wire which has a board|substrate.

Hereinafter, the structure of the oxide superconducting wire according to each embodiment will be described with reference to the drawings. These cross-sectional views schematically show a cross section perpendicular to the longitudinal direction of the superconducting wire. The vertical direction of the cross-sectional view is the thickness direction of the superconducting wire, and the horizontal direction of the cross-sectional view is the width direction of the superconducting wire.

FIG. 1 shows a superconducting wire according to the first embodiment. In the superconducting wire 10 of the first embodiment, the protective layer (first metal layer) 12 is laminated on the first surface 11a in the thickness direction of the oxide superconducting layer 11, and the second surface opposite to the first surface 11a. A protective layer 14 (second metal layer) is laminated on 11b. Further, a stabilizing layer (metal layer) 13 is laminated on the surface of the protective layer 12 opposite to the oxide superconducting layer 11. The

protective layers

12 and 14 may be referred to as the first protective layer 12 and the second protective layer 14 in some cases. The first protective layer 12 and the second protective layer 14 may have the same thickness, the same material, or the like, or may differ from each other in at least one of these viewpoints.

FIG. 2 shows a superconducting wire according to the second embodiment. The superconducting wire 10A of the second embodiment includes a first protective layer 12 laminated on the first surface 11a in the thickness direction of the oxide superconducting layer 11, and a stabilizing layer 13 laminated on the outer side of the first protective layer 12. A surface (second surface 11b) of the oxide superconducting layer 11 opposite to the first protective layer 12, a side surface of the oxide superconducting layer 11, a side surface of the first protective layer 12, and a stabilizing layer 13. And a second protective layer 14 laminated on the side surface.

FIG. 3 shows a superconducting wire according to the third embodiment. The superconducting wire 10B of the third embodiment includes a protective layer 12 laminated on the first surface 11a in the thickness direction of the oxide superconducting layer 11, a protective layer 14 laminated on the second surface 11b, and a stabilizing layer ( It has a first Cu metal layer 13 and a stabilizing layer (second Cu metal layer) 15. In addition, the respective stabilizing

layers

13 and 15 may be distinguished from each other to be referred to as a first stabilizing layer 13 and a second stabilizing layer 15.
The first stabilizing layer 13 is stacked on the surface of the protective layer 12 opposite to the oxide superconducting layer 11. The second stabilizing layer 15 is laminated on the surface of the protective layer 14 opposite to the oxide superconducting layer 11. The first stabilizing layer 13 and the second stabilizing layer 15 may have the same thickness, the same material, or the like, or may differ from each other in at least one of these viewpoints.

FIG. 4 shows a superconducting wire according to the fourth embodiment. The superconducting wire 10C of the fourth embodiment includes a first protective layer 12 laminated on the first surface 11a in the thickness direction of the oxide superconducting layer 11, and an outer side of the first protective layer 12 (oxidation of the first protective layer 12). Stabilization layer 13 laminated on the surface opposite to the oxide superconducting layer 11), the second surface 11b opposite to the first surface 11a of the oxide superconducting layer 11, and the side surface of the oxide superconducting layer 11. A second protective layer 14 laminated on the side surface of the first protective layer 12 and a side surface of the stabilizing layer 13, and a second stabilizing layer 15 laminated on the outer periphery of the superconducting wire 10C. The second stabilizing layer 15 covers the exposed surfaces of the first stabilizing layer 13 and the second protective layer 14.

In the

superconducting wire rods

10, 10A, 10B, and 10C of the above embodiment, the oxide superconducting layer 11 is composed of an oxide superconductor containing a rare earth element. Examples of the oxide superconductor include an RE-Ba-Cu-O-based oxide superconductor represented by the general formula REBa2Cu3O7-x (RE123). Examples of the rare earth element RE include one or more of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The oxide superconducting layer 11 has a thickness of, for example, about 0.5 to 5 μm.

The oxide superconducting layer 11 is a superconducting layer oriented in the plane direction. For example, the degree of orientation Δφ in the plane parallel to the thickness direction of the oxide superconducting layer 11 is preferably 6.0° or less. The oxide superconducting layer 11 may be a superconducting layer oriented in the entire width direction. The oxide superconducting layer 11 may be divided into two or more superconducting layers with a gap in a part in the width direction. Examples of the gap portion include a non-oriented portion, a void portion such as a groove, a conductor portion such as a metal, and an electrical insulating portion such as a resin. The non-oriented portion may be an oxide having a composition similar to that of the superconducting layer. In this case, each of the two or more superconducting layers preferably has a structure in which oriented superconducting layers are continuous in the longitudinal direction.

An artificial pin made of a different material may be introduced into the oxide superconducting layer 11 as an artificial crystal defect. Examples of different materials used to introduce artificial pins into the oxide superconducting layer 11 include BaSnO3 (BSO), BaZrO3 (BZO), BaHfO3 (BHO), BaTiO3 (BTO), SnO2, TiO2, ZrO2, LaMnO3, At least one kind of ZnO and the like can be mentioned.

The protective layers 12 and 14 have a function of bypassing an overcurrent generated at the time of an accident and suppressing a chemical reaction that occurs between the oxide superconducting layer 11 and the layers provided on the

protective layers

12 and 14. Have. Examples of the

protective layers

12 and 14 include a silver (Ag) layer or a layer containing Ag (for example, an Ag alloy layer). The Ag alloy preferably contains silver in a molar ratio or a weight ratio of 50% or more. In the above embodiment, the protective layer 12 is in contact with the first surface 11 a of the oxide superconducting layer 11 in the thickness direction, and the protective layer 14 is in contact with the second surface 11 b of the oxide superconducting layer 11. The thickness of the

protective layers

12 and 14 is preferably about 1 to 30 μm, and may be 10 μm or less, 5 μm or less, 2 μm or less when thinning the

protective layers

12 and 14.

The stabilizing layers 13 and 15 have functions such as bypassing an overcurrent generated at the time of an accident and mechanically reinforcing the oxide superconducting layer 11 and the

protective layers

12 and 14. Examples of the stabilizing

layers

13 and 15 include a copper (Cu) layer or a layer containing Cu (for example, a Cu alloy layer). It is preferable that the Cu alloy contains 50% or more of silver in a molar ratio or a weight ratio. In the above embodiment, the stabilizing layer 13 is in contact with one surface of the protective layer 12 in the thickness direction of the oxide superconducting layer 11, and the stabilizing layer 15 is in the thickness direction of the oxide superconducting layer 11. Touches one side of. The thickness of the stabilizing

layers

13 and 15 is not particularly limited, but is preferably about 1 to 300 μm, for example, 200 μm or less, 100 μm or less, 50 μm or less, 20 μm or the like.

In the

superconducting wire rods

10, 10A, 10B, 10C of the above-described embodiment, the

protective layers

12, 14 and the stabilizing

layers

13, 15 are provided as the metal layers 12, 13, 14, 15 on both surfaces in the thickness direction of the oxide superconducting layer 11. Because of the laminated structure, the cross-sectional area of the wire as a whole can be reduced. If the cross-sectional area of the wire as a whole can be reduced, the superconducting wire can be easily bent and deformed, and a superconducting coil wound to have a smaller diameter than in the conventional case can be formed. In addition, there are advantages that the superconducting wire can be made lighter and the fine wire can be easily processed. The protective layers 12 and 14 and the stabilizing

layers

13 and 15 can be formed by one or a combination of two or more of vapor deposition, sputtering, and plating (electrolytic plating, electroless plating, etc.).

The total thickness of the

superconducting wire rods

10, 10A, 10B, 10C in the thickness direction of the oxide superconducting layer 11 may be 10 to 1000 μm, for example, 500 μm or less, 300 μm or less, 200 μm or less, 100 μm or less, 70 μm or less, 50 μm or less. And so on. Here, the total thickness of the superconducting wire does not need to include all the configurations that can be attached to the superconducting wire, and for example, the outer surfaces of the metal layers 13, 14, 15 on both sides of the oxide superconducting layer 11 in the thickness direction. It may be the maximum distance between them. For example, the total thickness of the

superconducting wires

10 and 10A may be the distance between the outer surface of the stabilizing layer 13 and the outer surface of the second protective layer 14. The total thickness of the superconducting wire 10B may be the distance between the outer surface of the first stabilizing layer 13 and the outer surface of the second stabilizing layer 15. The total thickness of the superconducting wire 10C may be the distance between the outer surfaces on both sides of the second stabilizing layer 15 in the thickness direction.

The width of the superconducting wire is not particularly limited, but, for example, 1 to 20 mm. The length of the superconducting wire is not particularly limited, but is, for example, 1 m or more, and 10 m or more, 100 m or more, 200 m or more, 500 m or more, 1 km or more. It is also possible to connect a plurality of superconducting wires to form a longer wire. A short superconducting wire may be interposed while connecting the ends of the long superconducting wire in the longitudinal direction. The superconducting wire for connection may have a short length of, for example, 1 m or less. In order to suppress the influence of moisture or the like on the oxide superconducting layer 11, both sides in the width direction of the oxide superconducting layer 11 are preferably covered with metal layers such as the

protective layers

12 and 14 or the stabilizing

layers

13 and 15. ..

When manufacturing the superconducting wire of this embodiment, for example, as shown in FIG. 5, a method of manufacturing the superconducting wire 20 having a substrate and then removing the substrate may be adopted. In the manufacturing method of the present embodiment, the substrate used for forming the oxide superconducting layer 11 is composed of the metal substrate 21 and the intermediate layer 22. The metal substrate 21 is a tape-shaped metal substrate 21 having main surfaces on both sides in the thickness direction. Specific examples of the metal forming the metal substrate 21 include nickel alloys represented by Hastelloy (registered trademark), stainless steel, oriented Ni—W alloys in which a texture is introduced into nickel alloys, and the like. The thickness of the metal substrate 21 may be appropriately adjusted according to the purpose and is, for example, in the range of 10 to 1000 μm.

The intermediate layer 22 may have a multi-layered structure, and may have, for example, a diffusion prevention layer, a bed layer, an alignment layer, a cap layer, etc. in the order from the substrate side to the superconducting layer side. These layers are not always provided one by one, and some layers may be omitted or two or more layers of the same type may be repeatedly laminated. The intermediate layer 22 may be a metal oxide. By forming the oxide superconducting layer 11 on the intermediate layer 22 having excellent orientation, it becomes easy to obtain the oxide superconducting layer 11 having excellent orientation.

The diffusion prevention layer has a function of suppressing a part of components of the metal substrate 21 from being diffused and being mixed as an impurity into the oxide superconducting layer 11 side. The diffusion prevention layer is made of, for example, Si3N4, Al2O3, GZO (Gd2Zr2O7), or the like. The diffusion prevention layer has a thickness of 10 to 400 nm, for example.
The bed layer has a function of reducing the reaction at the interface between the metal substrate 21 and the oxide superconducting layer 11, and improving the orientation of the layer formed thereon. Examples of the material of the bed layer include Y2O3, Er2O3, CeO2, Dy2O3, Eu2O3, Ho2O3 and La2O3. The bed layer has a thickness of, for example, 10 to 100 nm.
The orientation layer is formed of a biaxially oriented material for controlling the crystal orientation of the cap layer. Examples of the material of the orientation layer include metal oxides such as Gd2Zr2O7, MgO, ZrO2-Y2O3 (YSZ), SrTiO3, CeO2, Y2O3, Al2O3, Gd2O3, Zr2O3, Ho2O3, and Nd2O3. This alignment layer is preferably formed by the IBAD method.
The cap layer is formed on the surface of the orientation layer, and is made of a material in which crystal grains can self-orient in the in-plane direction. Examples of the material of the cap layer include CeO2, Y2O3, Al2O3, Gd2O3, ZrO2, YSZ, Ho2O3, Nd2O3, LaMnO3 and the like. The thickness of the cap layer is in the range of 50 to 5000 nm.

The method for forming the intermediate layer 22 and the oxide superconducting layer 11 is not particularly limited as long as appropriate film formation is possible depending on the composition of the metal oxide. Examples of the film forming method include a dry film forming method such as a sputtering method, an evaporation method, an ion beam assisted film forming method (IBAD method), and a wet film forming method such as a sol-gel method. Examples of the vapor deposition method include an electron beam vapor deposition method, a pulse laser vapor deposition method (PLD method), and a chemical vapor deposition method (CVD method).

In the superconducting wire 20 shown in FIG. 5, after the step of laminating the oxide superconducting layer 11 on the metal substrate 21, the oxide superconducting layer 11 is formed on the side opposite to the metal substrate 21 in the thickness direction of the oxide superconducting layer 11. It can be manufactured by a step of laminating a metal layer composed of the protective layer 12 and the plating layer 23 on top. When the protective layer 12 is laminated on the oxide superconducting layer 11, heat treatment such as oxygen annealing may be performed. When the protective layer 12 is formed of an Ag layer or a layer containing Ag, oxygen gas can be passed through during heat treatment to supply oxygen to the oxide superconducting layer 11.

The plating layer 23 may have a front surface portion 23A laminated on the protective layer 12, a back surface portion 23B laminated on the back surface of the metal substrate 21, and a side surface portion 23C provided on a side surface of the superconducting wire 20. .. The side surface portion 23C may be removed prior to the step of removing the substrate. Thereby, as shown in FIG. 6, end faces in the width direction of each layer such as the metal substrate 21, the oxide superconducting layer 11 and the like may be exposed on the side surface of the stacked body 24. When removing the side surface portion 23C, a part of the oxide superconducting layer 11 may be removed. Examples of methods for removing the side surface portion 23C include mechanical processing such as grinding and laser processing.

When removing the metal substrate 21 as shown in FIG. 7, at least a part or all of the intermediate layer 22 may be removed. Moreover, on the surface of the oxide superconducting layer 11 after removing the metal substrate 21, the intermediate layer 22 may remain in at least a partial region in the width direction or the longitudinal direction.
Further, when the metal substrate 21 is removed, a part (for example, a part in the thickness direction) of the oxide superconducting layer 11 may be removed. As a method of removing the metal substrate 21, for example, a peeling method of applying a peeling force between the metal substrate 21 and the surface portion 23A of the plating layer can be mentioned. Alternatively, the substrate may be removed by mechanical processing such as grinding or laser processing. By removing the substrate from the superconducting wire 20, a laminate 25 having a structure having the protective layer 12 and the surface portion 23A of the plating layer on one surface of the oxide superconducting layer 11 is obtained. The surface portion 23A left in the laminated body 25 may form a part or the whole of the first stabilizing layer 13 in the superconducting wire according to the above embodiment.

On the side where the metal substrate 21 is removed in the thickness direction of the oxide superconducting layer 11, the above-mentioned second protective layer 14 and second stabilizing layer 15 are laminated as a metal layer on the oxide superconducting layer 11. As a result, the

superconducting wire rods

10, 10A, 10B, 10C of the above embodiment can be manufactured. When the second protective layer 14 is laminated on the oxide superconducting layer 11, heat treatment such as oxygen annealing may be performed. When the second protective layer 14 is composed of an Ag layer or a layer containing Ag, oxygen gas can be passed through during heat treatment to supply oxygen to the oxide superconducting layer 11.

On the outer periphery of the superconducting wire, an insulating tape such as polyimide may be wound or a resin layer may be formed in order to ensure electric insulation with respect to the surroundings of the superconducting wire. It should be noted that an insulating coating layer such as an insulating tape or a resin layer is not essential, and an insulating coating layer may be appropriately provided depending on the application of the superconducting wire rod, or the insulating coating layer may not be provided.
To make a superconducting coil using a superconducting wire, for example, after winding the required number of layers along the outer peripheral surface of the winding frame to form a coil-shaped multilayer winding coil, cover the wound superconducting wire. The superconducting wire can be fixed by impregnating with a resin such as epoxy resin.

The present invention has been described above based on the preferred embodiments, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. Modifications include addition, replacement, omission, and other changes of the constituent elements in each embodiment. It is also possible to appropriately combine the constituent elements used in the two or more embodiments.

The superconducting wire of the above embodiment does not require a substrate such as a metal, but in some cases, the substrate can be laminated on the outside of at least one metal layer in the thickness direction of the oxide superconducting layer. When laminating the substrate on the outer side of the metal layer, the substrate may be laminated over the entire length or width of the superconducting wire, or the substrate may be laminated only in a part of the longitudinal or width direction of the superconducting wire. Good. Alternatively, a reinforcing wire rod, a detection wire rod such as an optical fiber sensor, etc. may be vertically provided (arranged in parallel along the longitudinal direction) at the end portion in the width direction of the superconducting wire rod.

According to each of the above-described embodiments, since the metal layer having the Ag layer or the layer containing Ag is laminated in contact with both surfaces in the thickness direction of the oxide superconducting layer having crystal orientation, the conventional superconducting wire is oxidized. It is possible to provide a superconducting wire having excellent characteristics per unit cross-sectional area as compared with the substrate used for film formation remaining on one side in the thickness direction of the object superconducting layer.

10, 10A, 10B, 10C... Superconducting wire, 11... Oxide superconducting layer, 12, 14... Protective layer (metal layer), 13, 15... Stabilizing layer (metal layer), 20... Superconducting wire with substrate, 21... Metal substrate, 22... Intermediate layer, 23... Plating layer, 23A... Front surface portion, 23B... Back surface portion, 23C... Side surface portion, 24, 25... Laminated body

Claims

A superconducting wire having an oxide superconducting layer containing a rare earth element,
The oxide superconducting layer has an orientation degree Δφ in a plane parallel to the thickness direction of 6.0° or less,
The superconducting wire is
A first metal layer that is an Ag layer or a layer containing Ag, which is laminated on the first surface in the thickness direction of the oxide superconducting layer;
A second metal layer which is a Ag layer or a layer containing Ag, which is laminated on the second surface opposite to the first surface;
In the thickness direction of the oxide superconducting layer, in contact with the first metal layer or the second metal layer, a Cu layer or a metal layer containing Cu,
A superconducting wire rod.
The superconducting wire according to claim 1, wherein the metal layer has a first Cu metal layer in contact with the first metal layer and a second Cu metal layer in contact with the second metal layer.
The superconducting wire according to claim 1 or 2, wherein the first surface in the width direction of the oxide superconducting layer is covered with the first metal layer, and the second surface is covered with the second metal layer.
The superconducting wire according to any one of claims 1 to 3, wherein the total thickness of the superconducting wire in the thickness direction of the oxide superconducting layer is 50 μm or less.
A method of manufacturing a superconducting wire having an oxide superconducting layer containing a rare earth element,
A step of laminating the oxide superconducting layer on a substrate,
A step of laminating a first metal layer on the oxide superconducting layer on the side opposite to the substrate in the thickness direction of the oxide superconducting layer,
Removing the substrate,
A step of laminating a second metal layer on the oxide superconducting layer on the side where the substrate is removed in the thickness direction of the oxide superconducting layer,
And a method for manufacturing a superconducting wire.
The method for producing a superconducting wire according to claim 5, wherein the first metal layer and the second metal layer are Ag layers or layers containing Ag.
The method for producing a superconducting wire according to claim 6, wherein a Cu layer or a metal layer containing Cu is laminated so as to be in contact with the first metal layer or the second metal layer in the thickness direction of the oxide superconducting layer.