JP2018101536A - Oxide superconducting wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide superconducting wire structured such that an oxide superconducting layer resists degrading when bent, and the oxide superconducting wire has improved bending strength.SOLUTION: The present invention provides an oxide superconducting wire that has at least one recess 11c on one side 21 of a tape-like substrate 11. In the recess 11c, provided are an intermediate layer 12, an oxide superconducting layer 13, a protective layer 14, and an a stabilized layer 15, in a stacking manner in the stated order.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an oxide superconducting wire.

RE-Ba-Cu-O-based superconductors (RE is a rare earth element) represented by a general formula such as REBa ₂ Cu ₃ O _y (RE123) are superconductive at a temperature (˜90 K) exceeding the liquid nitrogen temperature (77 K). Showing gender. Since this oxide superconductor has a higher critical current density in a magnetic field than other high-temperature superconductors, applications such as coils and power cables are expected.

  In Patent Document 1, an intermediate layer is formed on a tape-shaped substrate by an ion beam assist method (IBAD) or the like, an oxide superconducting layer is formed on the surface of the intermediate layer, and Ag or the like is formed on the surface of the oxide superconducting layer. An oxide superconducting wire in which a protective layer is formed and a Cu electroplating layer is formed on the surface of the protective layer is described.

  Patent Document 2 discloses that the overcurrent is sufficiently bypassed only by the stabilization layer on the surface side by increasing the plating thickness on the surface on the superconducting layer side rather than the plating thickness on the back surface on the substrate side. In addition, it is described that the superconducting layer is located near the neutral line of the superconducting wire, and the tensile strain of the superconducting layer is suppressed.

JP 2007-80780 A Japanese Patent Laying-Open No. 2015-88414

  As described in Patent Document 2, when attempting to increase the plating thickness on the surface side, the plating thickness on the surface tends to be non-uniform due to the dog bone phenomenon in which the plating thickness at the corners becomes excessively thick. In that case, the thickness of the superconducting wire as a whole is likely to be non-uniform, which may hinder the superconducting wire from being coiled or cabled. In addition, as described in Patent Document 2, when using a method of arranging electrodes only on the front surface side, a method of bringing the back surface side closer to the wall surface of the plating tank, a method of masking the back surface side, etc., the apparatus is complicated. Thus, there is a problem that the cost of the plating process increases.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an oxide superconducting wire having a structure in which the oxide superconducting layer is hardly deteriorated by bending and the bending strength of the oxide superconducting wire is increased. And

  In order to solve the above-mentioned problems, the present invention has at least one concave portion on one surface of a tape-shaped substrate, and an intermediate layer, an oxide superconducting layer, a protective layer, and a stable layer in the concave portion. Provided is an oxide superconducting wire characterized in that the oxide layer is laminated in this order.

It is also possible to employ a configuration in which the depth of the concave portion is within a range of 10 to 60% of the thickness of the substrate.
It is also possible to adopt a configuration in which the stabilization layer is made of metal plating, conductive paste, or solder.
It is also possible to adopt a configuration in which the stabilization layer is composed of one type or two or more types of metal layers.
It is also possible to employ a configuration in which the stabilization layer is formed on at least a part of the outer peripheral surface of the substrate in addition to the recess.

  According to the present invention, since the intermediate layer, the oxide superconducting layer, the protective layer, and the stabilizing layer are laminated in the recess formed on one surface of the tape-shaped substrate, the oxide superconducting layer is bent. Deterioration is suppressed and the bending strength of the oxide superconducting layer can be improved.

It is sectional drawing which illustrates the oxide superconducting wire of 1st Embodiment. It is sectional drawing which illustrates the oxide superconducting wire of 2nd Embodiment.

  Hereinafter, based on a preferred embodiment, the present invention will be described with reference to the drawings.

  In FIG. 1, sectional drawing of the oxide superconducting wire of 1st Embodiment is shown. This sectional view schematically shows the structure of a cross section perpendicular to the longitudinal direction of the oxide superconducting wire. In the oxide superconducting wire of the present embodiment, at least one recess 11 c is provided on one surface (front surface) 21 of the tape-like substrate 11. In the recess 11 c of the substrate 11, the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are laminated to constitute the oxide superconductor 10. Further, a stabilization layer 15 is laminated at least on the protective layer 14 in the recess 11 c around the oxide superconductor 10.

In this specification, the longitudinal direction is the length direction of the oxide superconducting wire or its substrate 11. The thickness direction is a direction in which the layers such as the substrate 11, the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are laminated. The width direction is a direction perpendicular to the longitudinal direction and the thickness direction.
The outer peripheral surface 20 of the board | substrate 11 is on the surface except the inside of the recessed part 11c, for example, is one or more of the surface 21, the side surface 22, and the back surface 23.

  The substrate 11 is a tape-shaped metal substrate. On both sides in the thickness direction, each has a main surface (a front surface 21 and a back surface 23 opposite thereto). Specific examples of the metal constituting the substrate 11 include a nickel alloy typified by Hastelloy (registered trademark), stainless steel, an oriented Ni—W alloy in which a texture is introduced into the nickel alloy, and the like. What is necessary is just to adjust the thickness of the board | substrate 11 suitably according to the objective, for example, it is the range of 10-500 micrometers. A metal thin film (not shown) such as Ag or Cu may be formed on the side surface 22, the back surface 23, or both of the substrate 11 by sputtering or the like in order to improve the bonding property to the stabilization layer 15. The metal thin film may be integrated with the protective layer 14 formed on the surface of the oxide superconducting layer 13 in the recess 11c.

  The substrate 11 of the present embodiment has a concave portion 11 c in the thickness direction from the front surface 21 toward the back surface 23. The recess 11c can be formed by processing such as extrusion, grinding, wet etching, sand blasting, and laser. The recess 11c is preferably in the form of a groove that extends continuously in the longitudinal direction. The cross-sectional shape of the board | substrate 11 which has the recessed part 11c may be a shape which has the projection part 11b in two or more places at intervals in the width direction on one surface of the board | substrate main body 11a and the board | substrate body 11a, for example. The substrate body 11a and the protrusion 11b constitute an integrated metal substrate, whereby the strength of the substrate 11 against bending or the like can be maintained.

Examples of the depth of the recess 11 c include a range of 10 to 60% of the thickness of the substrate 11. Here, the thickness of the substrate 11 is the distance between the front surface 21 and the back surface 23. The depth of the recess 11c is the maximum distance (for example, the distance from the front surface 21 to the upper surface of the substrate body 11a) where the recess 11c exists in the thickness direction from the front surface 21 to the back surface 23 of the substrate 11.
Usually, each layer such as the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 is thinner than the thickness of the substrate 11, so that the oxide superconducting layer 13 approaches the neutral line of the substrate 11 in the thickness direction. It is preferable to set the depth of the recess 11c.

  The bottom surface of the recess 11c (the upper surface of the substrate body 11a) may be a curved surface, an inclined surface, or the like, but a plane substantially parallel to the front surface 21 or the back surface 23 is preferable. This facilitates control of the deposition conditions when the layers such as the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are stacked in the recess 11c. The side surface of the recess 11c (the side surface on the inner side in the width direction of the protrusion 11b) and the side surface 22 of the substrate 11 may be a curved surface, an inclined surface, or the like, or may be a plane that is substantially perpendicular to the front surface 21 or the back surface 23.

  The intermediate layer 12 is provided between the substrate 11 and the oxide superconducting layer 13. The intermediate layer 12 may have a multilayer structure, and may include a diffusion prevention layer, a bed layer, an alignment layer, a cap layer, and the like in order from the substrate 11 side to the oxide superconducting layer 13 side. These layers are not necessarily provided one by one, and some layers may be omitted, or two or more of the same kind of layers may be laminated repeatedly.

The diffusion preventing layer has a function of suppressing a part of the components of the substrate 11 from diffusing and mixing as impurities into the oxide superconducting layer 13 side. The diffusion preventing layer is made of, for example, Si ₃ N ₄ , Al ₂ O ₃ , GZO (Gd ₂ Zr ₂ O ₇ ) or the like. The thickness of the diffusion preventing layer is, for example, 10 to 400 nm.

A bed layer may be formed on the diffusion prevention layer in order to reduce the reaction at the interface between the substrate 11 and the oxide superconducting layer 13 and improve the orientation of the layer formed thereon. Examples of the material of the bed layer include Y ₂ O ₃ , Er ₂ O ₃ , CeO ₂ , Dy ₂ O ₃ , Eu ₂ O ₃ , Ho ₂ O ₃ , and La ₂ O ₃ . The thickness of the bed layer 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. Examples of the material of the alignment layer include 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 , Examples thereof include metal oxides such as Zr ₂ 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-align in the in-plane direction. The material of the cap layer, for _{example, 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, LaMnO 3 , and the like. Examples of the thickness of the cap layer include a range of 50 to 5000 nm.

The oxide superconducting layer 13 is composed of an oxide superconductor. As an oxide superconductor, particularly, but not limited to, for example, the general formula _{REBa 2 Cu 3 O y (RE123} ) with REBa-Cu-O based oxide superconductor represented the like. The rare earth element RE may be one or more of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Among these, one of Y, Gd, Eu, and Sm, or a combination of two or more of these elements is preferable. In general, y is 7-x (oxygen deficiency x: about 0 to about 1). The thickness of the oxide superconducting layer 13 is, for example, about 0.5 to 5 μm. This thickness is preferably uniform in the longitudinal direction at least in the recess 11c (on the substrate body 11a).

When the substrate 11 has recesses 11c at two or more positions with a gap in the width direction, and the oxide superconducting layer 13 provided in each recess 11c is divided by the protrusions 11b, each oxide superconducting layer 13 Is made thin (multifilament), the shielding current and the magnetization loss of the oxide superconducting wire can be reduced.
Alternatively, each oxide superconductor layer 13 or the like is formed in each recess 11c of the substrate 11 having the recesses 11c at two or more locations to produce the oxide superconductor 10, and then oxidized at one location or every predetermined number of recesses 11c. By cutting the superconductor 10, a plurality of oxide superconducting wires can be obtained.

  The protective layer 14 has functions such as bypassing overcurrent generated at the time of an accident and suppressing a chemical reaction occurring between the oxide superconducting layer 13 and a layer provided on the protective layer 14. Examples of the material of the protective layer 14 include silver (Ag), copper (Cu), gold (Au), an alloy of gold and silver, other silver alloys, copper alloys, and gold alloys. The protective layer 14 covers at least the surface of the oxide superconducting layer 13 (the surface opposite to the substrate 11 side in the thickness direction). Further, the protective layer 14 may cover at least a part of the outer peripheral surface 20 of the substrate 11. The protective layer 14 may be composed of two or more metal layers or two or more metal layers. The thickness of the protective layer 14 is, for example, about 1 to 30 μm, and may be 10 μm or less when the protective layer 14 is thinned.

  The stabilization layer 15 is laminated on the protective layer 14 in at least the recess 11 c around the oxide superconductor 10. The stabilization layer 15 may be formed only in the recess 11c. The stabilizing layer 15 may be formed on at least a part of the outer peripheral surface 20 of the substrate 11 in addition to the recess 11 c. The thickness of the stabilization layer 15 is, for example, about 15 to 300 μm.

  The stabilization layer 15 can be composed of a conductor layer (metal layer) such as metal plating, conductive paste, or solder. Examples of metals used for metal plating, conductive paste, and the like include Cu, Ag, Al, Sn, Ti, and the like. As the solder, for example, Sn-Pb-based, Pb-Sn-Sb-based, Sn-Pb-Bi-based, Bi-Sn-based, Sn-Cu-based, Sn-Pb-Cu-based, Sn-Ag-based solder, etc. , Sn alloys, In, In alloys, Zn, Zn alloys, Ga, Ga alloys and the like.

  The stabilization layer 15 may be composed of one type of metal layer, or may be composed of two or more types of metal layers. Each metal layer may be laminated so as to overlap on the recess 11 c or the outer peripheral surface 20. Different types of metal layers may be formed in different portions of the recess 11c or the outer peripheral surface 20, respectively. Each metal layer (conductor layer) may be composed of one kind of metal element, or may contain two or more kinds of metal elements (alloy, mixture, etc.).

  The first embodiment shown in FIG. 1 is an example in which the stabilization layer 15 fills the recess 11c. For example, as in the second embodiment shown in FIG. 2, the stabilization layer 15 above the oxide superconducting layer 13 may have a recess in the recess 11c. The thickness of the stabilization layer 15 above the oxide superconducting layer 13 may be approximately the same as the thickness of the stabilization layer 15 on the outer peripheral surface 20 of the substrate 11.

According to the oxide superconducting wire of this embodiment, since the position of the oxide superconducting layer 13 in the thickness direction approaches the neutral line of the oxide superconducting wire, deterioration and damage of the oxide superconducting layer 13 against bending are suppressed, Bending strength is improved.
Further, as described in Patent Document 2, the thickness of the stabilization layer 15 can be suppressed as compared with the case where a thick stabilization layer is formed on the surface of the flat substrate. Thereby, the current density when wound in a coil shape can be improved.
Moreover, since the side surface of the oxide superconducting layer 13 is covered with the protrusion 11b of the substrate 11, cracks, damage, etc. of the oxide superconducting layer 13 can be suppressed when the wire is bent, Intrusion of moisture can be prevented.

  To make a superconducting coil using a tape-shaped oxide superconducting wire, the superconducting wire is wound around the outer peripheral surface of the winding frame to form a coil shape (multi-layer winding coil) and then wound. The superconducting wire can be fixed by impregnating a resin (insulating resin) such as an epoxy resin so as to cover the wire.

  As mentioned above, although this invention has been demonstrated based on suitable embodiment, this invention is not limited to the above-mentioned embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

  The superconducting wire can have an external terminal. The portion having the external terminal may have a different cross-sectional structure from other portions.

  Hereinafter, the present invention will be specifically described with reference to examples. In addition, this invention is not limited only to these Examples.

<Preparation of substrate having recesses>
(1) Three recesses are formed on the surface of a substrate (width 12 mm × length 1000 mm × thickness 0.75 mm) of Hastelloy (registered trademark) C-276 (trade name of US Haynes Co., Ltd.) at intervals in the width direction. did.
(2) The outer peripheral surface of the substrate having a recess and the inside of the recess were polished.
(3) The substrate was degreased and washed with acetone.

<Production of oxide superconductor>
(4) A diffusion prevention layer of Al ₂ O ₃ was formed on the substrate by ion beam sputtering.
(5) A bed layer of Y ₂ O ₃ was formed on the diffusion prevention layer by ion beam sputtering.
(6) An MgO alignment layer was formed on the bed layer by ion beam assisted deposition.
(7) A CeO ₂ cap layer was formed on the alignment layer by pulsed laser deposition.
(8) An oxide superconducting layer of GdBa ₂ Cu ₃ O _7-x was formed on the cap layer by a pulse laser deposition method.
(9) A protective layer of Ag was formed mainly on the oxide superconducting layer by sputtering from the upper surface side (surface direction) of the oxide superconducting layer.
(10) Oxygen annealing of the oxide superconductor was performed.
(11) The oxide superconductor was slit to a width of 4 mm.

<Formation of stabilization layer>
(12) Cu was deposited on the upper surface (substrate surface side) and lower surface (substrate rear surface side) of the oxide superconductor by sputtering.
(13) Cu was deposited on the entire circumference of the oxide superconductor by plating, and the recess was filled with a Cu plating layer. Here, Ag paste, solder, or the like may be used instead of Cu plating.

  According to these examples, in the oxide superconducting wire, deterioration of the oxide superconducting layer due to bending can be suppressed, and the bending strength of the oxide superconducting layer can be improved.

DESCRIPTION OF SYMBOLS 10 ... Oxide superconductor, 11 ... Board | substrate, 11a ... Board | substrate main body, 11b ... Projection part, 11c ... Recessed part, 12 ... Intermediate | middle layer, 13 ... Oxide superconducting layer, 14 ... Protective layer, 15 ... Stabilization layer, 20 ... The outer peripheral surface of the substrate, 21... The surface of the substrate (one surface), 22... The side surface of the substrate, 23.

Claims (5)

Having at least one recess on one surface of the tape-shaped substrate;
An oxide superconducting wire, wherein an intermediate layer, an oxide superconducting layer, a protective layer, and a stabilizing layer are laminated in this order in the recess.   2. The oxide superconducting wire according to claim 1, wherein a depth of the recess is in a range of 10 to 60% of a thickness of the substrate.   The oxide superconducting wire according to claim 1 or 2, wherein the stabilizing layer is made of metal plating, conductive paste, or solder.   The oxide superconducting wire according to claim 1 or 2, wherein the stabilization layer is composed of one or more metal layers.   5. The oxide superconducting wire according to claim 1, wherein the stabilization layer is formed on at least a part of an outer peripheral surface of the substrate in addition to the recess.

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