JP6484658B2 - Oxide superconducting wire and superconducting coil - Google Patents

Description

  The present invention relates to an oxide superconducting wire and a superconducting coil.

Among oxide superconducting wires, a RE-Ba-Cu-O-based superconductor represented by a general formula such as REBa ₂ Cu ₃ O _7-δ (RE123) (where RE represents a rare earth) is tape-shaped. The oxide superconducting wire formed on the substrate has a high critical current in a magnetic field and a high tensile strength in the longitudinal direction of the wire. However, it is known that this type of oxide superconducting wire is relatively weak against a force perpendicular to the main surface of the tape-shaped substrate. When a force in a direction perpendicular to the substrate is applied, the properties of the wire may be deteriorated by peeling or breaking of the superconducting layer.

  As a countermeasure against such deterioration, Patent Document 1 discloses that the stabilizing material includes an upper plate and a lower plate, and the upper plate and the lower plate are electrically and mechanically connected at both ends in the width direction over the longitudinal direction. An oxide superconducting wire is disclosed. It is described that a stress can be relieved even if stress is applied to the oxide superconducting wire by forming a hollow portion between the upper plate and the lower plate or by overlapping the upper plate and the lower plate. Yes.

Japanese Patent No. 5847709

  However, in the case of the structure described in Patent Document 1, the structure of the stabilizing material becomes complicated, and there is a problem that the current density decreases due to the thickening of the stabilizing material.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the oxide superconducting wire and superconducting coil which can suppress the deterioration of the characteristic with respect to the force of the direction perpendicular | vertical to a board | substrate.

  In order to solve the above problems, an oxide superconducting layer is formed on a tape-like substrate through an intermediate layer, and at least a surface of the oxide superconducting layer is provided with a protective layer and a stabilizing layer. The oxide superconductivity is characterized in that at least a part of both end portions in the width direction of the two substrates is fixed, and a central portion in the width direction of the two substrates is not fixed. Provide wire rods.

  The fixing portions at both ends in the width direction of the two substrates may be welded portions.

  The present invention also provides a superconducting coil using the oxide superconducting wire.

  According to the present invention, even when a force in a direction perpendicular to the substrate is applied, it is possible to suppress deterioration of characteristics due to peeling of the oxide superconducting layer.

It is sectional drawing which illustrates the oxide superconducting wire of 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 embodiment is shown. This sectional view schematically shows the structure of a cross section perpendicular to the longitudinal direction of the oxide superconducting wire 10. The oxide superconducting wire 10 of this embodiment includes a superconducting laminate 15 in which an oxide superconducting layer 13 is formed on a substrate 11 with an intermediate layer 12 interposed.

  The superconducting laminate 15 of the present embodiment has a configuration in which an intermediate layer 12, an oxide superconducting layer 13, and a protective layer 14 are laminated in this order on a tape-like substrate 11 and one surface of the substrate 11. In this specification, the 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 is the thickness direction. The width direction is a direction perpendicular to the longitudinal direction and the thickness direction. The side surface of the superconducting laminate 15 is one or both of the side surfaces on both sides in the width direction.

  The substrate 11 is a tape-shaped metal substrate having a width of about 10 mm, and has main surfaces on both sides in the thickness direction. The main surface is one surface and the back surface opposite to the one surface. 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.

  The substrate 11 of the present embodiment has a configuration in which two substrates 11a and 11b are stacked in the thickness direction. The two substrates 11a and 11b have a fixing portion 17 to which at least a part of both end portions in the width direction is fixed, and a non-fixing portion 18 in which the central portion in the width direction is not fixed. The intermediate layer 12 and the oxide superconducting layer 13 are stacked on one side of the substrate 11b. That is, the superconducting laminate 15 of this embodiment includes a substrate 11b on which the intermediate layer 12 and the oxide superconducting layer 13 are laminated, and a substrate 11a on which the intermediate layer 12 and the oxide superconducting layer 13 are not laminated.

  The materials constituting the plurality of substrates 11a and 11b may be the same as or different from each other.

  Examples of the fixing portion 17 include a welded portion formed by welding the substrates 11a and 11b. In the non-fixed portion 18, the opposing surfaces of the substrates 11a and 11b may be in contact with each other, and there may be a gap between the substrates 11a and 11b. The non-adhering portion 18 may be coated and filled with a non-adhesive material such as a fluorine resin, a silicone resin, or oil. In addition, as a non-adhesive material, a temperature-sensitive pressure-sensitive adhesive, adhesive, or the like that does not have adhesion at a low temperature at which the oxide superconducting layer 13 is in a superconducting state and has adhesion at a higher temperature is used. Is also possible. By providing the non-adhered portion 18, the stress is relaxed even when a stress in a direction perpendicular to the substrate is applied, and peeling and destruction of the oxide superconducting layer 13 can be suppressed.

  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 X (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. Generally, X is 7-x (oxygen deficiency x: about 0 to 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.

  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. Here, the surface of the oxide superconducting layer 13 is a surface opposite to the substrate 11 side in the thickness direction.

  Furthermore, the protective layer 14 may cover a part or all of a region selected from the side surface of the oxide superconducting layer 13, the side surface of the intermediate layer 12, the side surface and the back surface of the substrate 11. The protective layer 14 may be composed of two or more metal layers or two or more metal layers. Although the thickness of the protective layer 14 is not specifically limited, For example, about 1-30 micrometers is mentioned. When the protective layer 14 is thinned, it may be 10 μm or less.

  In the present embodiment, the procedure for producing the superconducting laminate 15 is not particularly limited, but after the fixing portion 17 is formed on the two substrates 11a and 11b, the intermediate layer 12 and the oxide superconducting layer are formed on one substrate 11b. 13 and the protective layer 14 may be laminated in order. After the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are sequentially stacked on one substrate 11b, the other substrate 11a may be overlaid on the back surface of the substrate 11b to form the fixing portion 17.

  The thickness of the board | substrate 11a is the range of 5-250 micrometers, for example. The thickness of the substrate 11b is, for example, in the range of 5 to 250 μm. The ratio of the thicknesses of the substrates 11a and 11b is not particularly limited, and examples thereof include 1%: 99% to 99%: 1%. As specific examples of the ratio of the thicknesses of the substrates 11a and 11b, 10%: about 90%, 20%: about 80%, 30%: about 70%, 40%: about 60%, 50%: about 50%, 60 %: About 40%, 70%: about 30%, 80%: about 20%, 90%: about 10%.

  When the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are laminated on the substrate 11b before the two substrates 11a and 11b are overlaid, the thickness of the substrate 11b is preferably larger than the thickness of the substrate 11a. . In this case, by ensuring the thickness of the substrate 11b on the side where the oxide superconducting layer 13 is laminated, the intermediate layer 12, the oxide superconducting layer 13, the protective layer 14 and the like can be easily formed. That is, by performing the film formation while moving the substrate 11b having a high tensile strength in the longitudinal direction, it is possible to easily realize a long and uniform film formation in the longitudinal direction. In order to easily perform film formation while moving in the longitudinal direction, for example, the thickness of the substrate 11b is preferably 10 μm or more, and more preferably 30 μm or more.

  When the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are stacked on the substrate 11 in which the two substrates 11a and 11b are overlapped, it is preferable to reduce the thickness of each of the substrates 11a and 11b. Since the substrates 11a and 11b of the stacked substrate 11 can share the tensile load during film formation, an increase in the total thickness of the substrates 11a and 11b can be suppressed.

  Decreasing the current density can be suppressed by thinning the entire stacked substrate 11. For example, if the materials and thicknesses of the two substrates 11a and 11b are the same, it is not necessary to prepare different substrates, and the cost can be reduced. Further, when the substrate 11a is deformed by making the substrate 11a on the side on which the oxide superconducting layer 13 is not laminated thinner than the substrate 11b on the side on which the oxide superconducting layer 13 is laminated, The influence can be suppressed.

  The positions where the fixing portions 17 are formed at both ends in the width direction may be the same position or different positions in the longitudinal direction. The fixing portions 17 on one end side in the width direction and the fixing portions 17 on the other end side may be alternately arranged along the longitudinal direction. By alternately arranging, one end side where the fixing portion 17 is formed and the other end side where the fixing portion 17 is not formed can be alternately arranged in a well-balanced manner. When the fixing portions 17 at both ends in the width direction are continuously formed in the longitudinal direction, even if there is a gap in the non-fixing portion 18, it is difficult for a substance to enter the gap from the outside. When the stabilization layer 16 is formed by metal plating, a non-adhesive material that repels a chemical used for plating may be provided in the non-fixed portion 18. When the fixing portions 17 at both ends in the width direction are intermittently formed in the longitudinal direction, the fixing portions 17 are formed with a length of 10 to 100 μm in the longitudinal direction of the oxide superconducting wire 10, and 10 to 100 μm. Adjacent adhering portions 17 are formed with an interval of. In the cross-sectional view of the oxide superconducting wire 10, the width of the fixing portion 17 is 5 to 500 μm, preferably 10 to 200 μm. In a cross-sectional view of the oxide superconducting wire 10, the width of the fixing portion 17 is 0.05 to 5.0%, preferably 0.10 to 2.0% with respect to the width of the oxide superconducting wire 10.

  The oxide superconducting wire 10 of this embodiment has a stabilizing layer 16 made of metal such as metal plating or metal foil on the outer periphery of the superconducting laminate 15. The stabilization layer 16 is a part of a region selected from the surface of the protective layer 14, the side surface of the protective layer 14, the side surface of the oxide superconducting layer 13, the side surface of the intermediate layer 12, the side surface of the substrate 11, and the back surface of the substrate 11. You may cover everything. Here, the surface of the protective layer 14 is a surface opposite to the substrate 11 side in the thickness direction. Although it does not specifically limit as thickness of the stabilization layer 16, For example, about 10-300 micrometers is mentioned.

  The order of the process of forming each layer of the superconducting laminate 15 and the process of forming the stabilization layer 16 can be selected as appropriate. For example, the stabilization layer 16 may be formed after the fixing portion 17 is formed between the two substrates 11a and 11b. It is also possible to overlap the two substrates 11a and 11b after the stabilization layer 16 is formed on the outer periphery of the superconducting laminate 15 that does not have the substrate 11a. The film forming conditions of the stabilization layer 16 may be controlled so that the stabilization layer 16 does not adhere between the substrates 11a and 11b.

As an example of the manufacturing process of the oxide superconducting wire 10, the following illustration is mentioned, for example.
(1) A method in which the fixing layer 17 is formed between the substrates 11a and 11b, and then the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are sequentially stacked on the substrate 11 and then the stabilization layer 16 is formed. .
(2) After the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are sequentially laminated on the substrate 11b, the substrates 11a and 11b are overlapped to form the fixing portion 17, and then the stabilization layer 16 is formed. how to.

  In the case where the stabilization layer 16 is made of a highly conductive metal, it is possible to provide a function as a bypass part that commutates an overcurrent generated when the oxide superconducting layer 13 transitions to a normal conducting state. Examples of the highly conductive metal include metals such as copper, copper alloy, aluminum, aluminum alloy, and silver. Further, when the oxide superconducting wire 10 is used for a superconducting fault current limiter, it is necessary to instantaneously suppress the overcurrent generated at the time of transition to the normal conducting state, so that a high resistance metal is suitable for the stabilization layer 16. Used for. Examples of the high resistance metal include Ni-based alloys such as Ni-Cr.

  When the stabilization layer 16 covers the surface of the oxide superconducting layer 13 or the protective layer 14, the electrical connection between the oxide superconducting layer 13 and the stabilization layer 16 is good. Furthermore, when the stabilization layer 16 covers the side surface of the oxide superconducting layer 13, it is possible to improve the peeling prevention property and waterproofness of the oxide superconducting layer 13. When the stabilization layer 16 is made of a metal foil, it may be fixed to the outer periphery of the superconducting laminate 15 via a bonding material such as solder.

  To produce a superconducting coil using a tape-shaped oxide superconducting wire, a superconducting wire is wound around the outer peripheral surface of the winding frame to form a coil-shaped multilayer winding coil, and then the wound superconducting coil is formed. The superconducting wire can be fixed by impregnating a resin such as an epoxy resin so as to cover the wire.

  In the case of a superconducting coil in which an oxide superconducting wire is wound in a coil shape and impregnated with a resin such as an epoxy resin, it is perpendicular to the substrate during cooling due to the difference in thermal expansion coefficient between the oxide superconducting wire and the resin during cooling. Tensile stress in various directions may work. In addition, when the superconducting coil is energized, stress acting in the direction of expanding the superconducting coil outward may act as hoop stress or the like. According to the present embodiment, since the non-adhered portion is provided between the two substrates 11a and 11b, the stress is relieved even if the stress in the direction perpendicular to the substrate is applied, and the oxide superconducting layer 13 is peeled or broken. Can be suppressed. As a result, the characteristics of the oxide superconducting wire 10 are unlikely to deteriorate.

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.

DESCRIPTION OF SYMBOLS 10 ... Oxide superconducting wire, 11, 11a, 11b ... Board | substrate, 12 ... Intermediate | middle layer, 13 ... Oxide superconducting layer, 14 ... Protective layer, 15 ... Superconducting laminated body, 16 ... Stabilizing layer, 17 ... Adhering part, 18 ... Non-fixed part.

Claims (3)

An oxide superconducting layer is formed on the tape-shaped substrate via an intermediate layer, and a protective layer and a stabilizing layer are provided on at least the surface of the oxide superconducting layer,
Two substrates are stacked as the substrate, at least a part of both ends in the width direction of the two substrates is fixed, and a central portion in the width direction of the two substrates is not fixed. Oxide superconducting wire.   2. The oxide superconducting wire according to claim 1, wherein the fixing portions at both ends in the width direction of the two substrates are welded portions.   A superconducting coil in which the oxide superconducting wire according to claim 1 or 2 is used.