JP2013004194A - Method for manufacturing oxide superconducting wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an oxide superconducting wire capable of manufacturing an oxide superconducting wire in which variations of the superconducting characteristics are reduced in the longitudinal direction of the wire.SOLUTION: A method for manufacturing an oxide superconducting wire includes: a first step S10 for preparing a superconductive laminate in which an intermediate layer, an oxide superconductive layer and a stabilization layer are laminated, in this order, on the surface of a tape-shaped base material; and a second step S20 for thinning the thickness of the base material by polishing the back surface of the base material of the superconductive laminate.

Description

  The present invention relates to a method for producing an oxide superconducting wire.

RE-123 oxide superconductor discovered in recent years (REBa ₂ Cu ₃ O _{7-X, where} RE is a rare earth element including Y) exhibits superconductivity above liquid nitrogen temperature and has low current loss. It is considered as a very promising material for practical use, and it is desired to process it into a wire and use it as a power supply conductor or a magnetic coil. As a method for processing this oxide superconductor into a wire, an intermediate layer (polycrystalline intermediate thin film) having good crystal orientation is formed on a tape-shaped metal substrate by a film forming method, and RE is formed on this intermediate layer. A technique for stacking and forming an oxide superconducting layer made of a −123 oxide superconductor is known (see, for example, Patent Documents 1 and 2).
In addition, in order to put such a superconducting wire into practical use, it is required to make the wire thinner from the viewpoint of handleability and workability. As a method of thinning the superconducting wire, there is a method of using a thinner metal substrate instead of a metal substrate that is usually about 100 μm thick. For example, a superconductor substrate thinned to a thickness of 75 μm A material is disclosed (see Patent Document 3).

JP 2005-330533 A Japanese Patent Laid-Open No. 11-86647 Japanese Patent Laid-Open No. 2007-200831

In order to manufacture this type of tape-shaped oxide superconducting wire, a tape-shaped metal substrate feed reel and take-up reel are provided in the film forming chamber of the film forming apparatus, and this is necessary for the metal substrate fed from the send reel. After the film is laminated, the metal substrate needs to be wound up. Moreover, when manufacturing oxide superconducting wires having a laminated structure, a plurality of layers including various layers such as a diffusion preventing layer, various underlayers, an orientation intermediate layer, an oxide superconducting layer, and a stabilizing layer are combined with each material. It is necessary to form a film on a metal substrate with a film forming apparatus. Furthermore, when a thick layer is formed, in order to increase the film formation efficiency, a combination of rollers is provided so that the metal substrate can pass through the film formation region of the film formation chamber a plurality of times. It is also possible to use a film forming apparatus configured to reciprocate a plurality of times.
However, if a metal substrate thinner than usual is used and a film is formed on this metal substrate under the same conditions as before, the tension and temperature applied to the metal substrate moved through the roller will be different. There is a possibility that an oxide superconducting layer cannot be formed with good crystal orientation, resulting in a superconducting wire having low superconducting properties. In order to produce a high-performance oxide superconducting wire, it is necessary to optimize the film forming conditions and to modify the film forming apparatus.

  Further, as a result of examination by the present inventors, when a superconducting wire is produced by forming an oxide superconducting layer on a wavy tape-like metal substrate via an intermediate layer, variation in superconducting characteristics occurs in the longitudinal direction of the wire. It has been found. Furthermore, it has been found that even when a superconducting wire is produced by selectively using a metal substrate with less waviness, variation in superconducting characteristics may also occur in the longitudinal direction of the wire. This is a reel-to-reel method in which when a superconducting wire is manufactured using a long tape-shaped metal substrate, film formation is usually performed while the substrate wound around one reel is fed out to the other reel. Although each layer is formed, it is considered that swell and internal stress may be generated in the metal substrate due to winding on the reel in this film forming process. In addition, since the oxide superconducting layer is exposed to a high-temperature environment when it is formed, it may be presumed that stress may remain in the base material due to thermal history.

  The present invention has been made in view of the above-described conventional situation, and an object thereof is to provide an oxide superconducting wire manufacturing method capable of manufacturing an oxide superconducting wire with a small variation in superconducting characteristics in the longitudinal direction of the wire. And

In order to solve the above problems, the method for producing an oxide superconducting wire according to the present invention includes a superconducting laminate in which an intermediate layer, an oxide superconducting layer, and a stabilizing layer are laminated in this order on the surface of a tape-like substrate. And a second step of polishing the back surface of the base material of the superconducting laminate to reduce the thickness of the base material.
According to the method for manufacturing an oxide superconducting wire of the present invention, a superconducting laminate in which an intermediate layer, an oxide superconducting layer, and a stabilizing layer are laminated on the surface side of the substrate is prepared, and the substrate of the superconducting laminate is prepared. By polishing the back surface, the swell of the substrate can be reduced, and the residual stress (strain) of the substrate can be reduced. Therefore, since the stress distribution in the longitudinal direction of the substrate is reduced, the stress applied to the oxide superconducting layer is small and uniform in the longitudinal direction of the wire, the oxide has a small variation in superconducting characteristics in the longitudinal direction of the wire Superconducting wire can be manufactured.
Moreover, the manufacturing method of the oxide superconducting wire of this invention is the structure which makes the thickness of a base material thin by grind | polishing the back surface A of the base material of this superconducting laminated body, after producing a superconducting laminated body. Therefore, each layer can be formed under optimized conditions using a base material having a normal thickness, so that an oxide superconducting layer with good crystal orientation can be formed, and the base material can be maintained in a state in which the crystal orientation is maintained. Since it can be thinned by polishing, a thin oxide superconducting wire having good characteristics can be manufactured.

In the method for producing an oxide superconducting wire according to the present invention, in the first step, the tape-shaped base material is wound around a delivery reel, and the winding termination portion of the base material wound around the delivery reel is drawn out and wound. A film formation region where vapor deposition particles fly between the delivery reel and the take-up reel, and the base material is fed from the supply reel to the take-up reel. By passing the substrate through and depositing the vapor deposition particles on the substrate, at least one of the intermediate layer, the oxide superconducting layer, and the stabilizing layer can be formed.
In this case, in the film forming process of each layer on the base material, undulation or internal stress may occur in the base material due to winding on a reel, etc., but the back surface of the base material is polished after the film formation of each layer. Thus, the swell generated in the base material can be reduced, and the residual stress (strain) of the base material can be reduced. Therefore, since the stress distribution in the longitudinal direction of the substrate is reduced, the stress applied to the oxide superconducting layer is small and uniform in the longitudinal direction of the wire, the oxide has a small variation in superconducting characteristics in the longitudinal direction of the wire Superconducting wire can be manufactured.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the oxide superconducting wire which can manufacture the oxide superconducting wire with a small dispersion | variation in the superconducting characteristic of a wire longitudinal direction can be provided.

It is a section perspective view showing typically an example structure of an oxide superconducting wire obtained by a manufacturing method of an oxide superconducting wire of the present invention. It is a flowchart which shows an example of the manufacturing method of the oxide superconducting wire which concerns on this invention. In the manufacturing method of the oxide superconducting wire which concerns on this invention, it is explanatory drawing which shows an example of the process of forming an oxide superconducting layer on a base material using PLD method. It is a graph which shows the relative height of the back surface of the base material in the oxide superconducting wire of Example 1 and Comparative Example 1. It is a graph which shows distribution of the critical current value of the longitudinal direction in the oxide superconducting wire of Example 1 and Comparative Example 1.

Hereinafter, embodiments of a method for producing an oxide superconducting wire according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional perspective view schematically showing an example structure of an oxide superconducting wire obtained by the method for producing an oxide superconducting wire according to the present invention, and FIG. 2 shows an oxide superconducting wire producing method according to the present invention. It is a flowchart which shows an example.

The oxide superconducting wire 10 obtained by the method for manufacturing an oxide superconducting wire according to the present invention has an intermediate layer 12 and an oxidation layer on one surface (surface) of a long tape-like base material 11 as shown in FIG. The superconducting layer 13 and the stabilization layer 14 are sequentially laminated.
In order to obtain the oxide superconducting wire 10 having the structure shown in FIG. 1, an oxide superconducting wire manufacturing method according to the present invention includes an intermediate layer 12 and an oxide superconducting layer on the surface (one surface) of a tape-like substrate 11. The first step S10 for preparing a superconducting laminate in which 13 and the stabilizing layer 14 are laminated in this order, and the back surface (the other surface) 11A of the substrate 11 of the superconducting laminate are polished to obtain the thickness of the substrate 11 A second step S20 for reducing the thickness.
As shown in FIG. 2, the first step S10 includes an intermediate layer forming step S11 for forming the intermediate layer 12 on the substrate 11, and an oxide superconducting layer forming step S12 for forming the oxide superconducting layer 13 on the intermediate layer 12. And a stabilization layer forming step S13 for forming the stabilization layer 14 on the oxide superconducting layer 13. Moreover, 2nd process S20 is equipped with grinding | polishing process S21 of the base material back surface which grind | polishes the back surface 11A of the base material 11 of the superconducting laminated body formed at 1st process S10. Hereafter, each process of the manufacturing method of the oxide superconducting wire of this invention is demonstrated in process order.

[First step S10]
(Intermediate layer forming step S11)
First, the tape-shaped base material 11 is prepared.
The tape-shaped base material 11 may be any material that can be used as a base material for ordinary superconducting wires, and is preferably made of a heat-resistant metal. Here, the tape-shaped substrate 11 includes a long plate shape and a long sheet shape in addition to the tape shape. Among heat resistant metals, an alloy is preferable, and a nickel (Ni) alloy or a copper (Cu) alloy is more preferable. Among them, if it is a commercial product, Hastelloy (trade name, manufactured by Haynes) is suitable, and the amount of components such as molybdenum (Mo), chromium (Cr), iron (Fe), cobalt (Co) is different, Hastelloy B, Any kind of C, G, N, W, etc. can be used. Further, as the base material 11, an oriented metal base material in which a texture is introduced into a nickel (Ni) alloy or the like may be used.
What is necessary is just to adjust the thickness of the base material 11 suitably according to the objective, Usually, it is preferable that it is 10-500 micrometers, and it is more preferable that it is 20-200 micrometers. By setting the lower limit value or more, the strength can be further improved, and by setting the upper limit value or less, the critical current density of the overall can be further improved.

Next, the intermediate layer 12 is formed on the surface of the substrate 11.
The intermediate layer 12 controls the crystal orientation of the oxide superconducting layer 13 and prevents diffusion of the metal element in the base material 11 into the oxide superconducting layer 13. Furthermore, it functions as a buffer layer that alleviates the difference in physical properties (thermal expansion coefficient, lattice constant, etc.) between the base material 11 and the oxide superconducting layer 13, and the material has physical properties that are different from those of the base material 11 and oxide. A metal oxide showing an intermediate value with the superconducting layer 13 is preferable. Specifically, preferred materials for the intermediate layer 12 are 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. Examples thereof include metal oxides such as O ₃ , Zr ₂ O ₃ , Ho ₂ O ₃ , and Nd ₂ O ₃ .
The intermediate layer 12 may be a single layer or a plurality of layers. For example, the layer made of the metal oxide (metal oxide layer) preferably has crystal orientation, and when it is a plurality of layers, the outermost layer (the layer closest to the oxide superconducting layer 13). Preferably have at least crystal orientation.

The intermediate layer 12 may have a multi-layer structure in which a bed layer is interposed on the substrate 11 side. The bed layer has high heat resistance and is used for reducing interfacial reactivity, and is used for obtaining the orientation of a film disposed thereon. Such a bed layer is arranged as necessary, and is made of, for example, yttria (Y ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ , also referred to as “alumina”), or the like. Is done. This bed layer can be formed, for example, by a film forming method such as a sputtering method, and the thickness thereof is, for example, 10 to 200 nm.

Further, in the present invention, the intermediate layer 12 may have a multi-layer structure in which a diffusion prevention layer and a bed layer are laminated on the base material 11 side. In this case, a diffusion preventing layer is interposed between the base material 11 and the bed layer. The diffusion preventing layer is formed for the purpose of preventing the diffusion of the constituent elements of the substrate 11, and is composed of silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), rare earth metal oxide, or the like. The thickness is, for example, 10 to 400 nm. Note that since the crystallinity of the diffusion preventing layer is not questioned, it may be formed by a film forming method such as a normal sputtering method.
In this way, by interposing the diffusion preventing layer between the base material 11 and the bed layer, when forming the other layer constituting the intermediate layer 12, the oxide superconducting layer 13 or the like, it is inevitably heated. When receiving a thermal history as a result of the heat treatment, it is possible to effectively suppress a part of the constituent elements of the base material 11 from being diffused to the oxide superconducting layer 13 side through the bed layer. As an example of the case where a diffusion preventing layer is interposed between the base material 11 and the bed layer, a combination using Al ₂ O ₃ as the diffusion preventing layer and Y ₂ O ₃ as the bed layer can be exemplified.

  The intermediate layer 12 may have a multi-layer structure in which a cap layer is further laminated on the metal oxide layer. The cap layer has a function of controlling the orientation of the oxide superconducting layer 13, diffuses the elements constituting the oxide superconducting layer 13 into the intermediate layer 12, and uses a gas and an intermediate used when the oxide superconducting layer 13 is laminated. It has a function of suppressing the reaction with the layer 12 and the like.

The cap layer is formed through a process of epitaxially growing on the surface of the metal oxide layer, and then growing the grains in the lateral direction (plane direction) (overgrowth) and selectively growing the crystal grains in the in-plane direction. The ones made are preferred. Such a cap layer has a higher degree of in-plane orientation than the metal oxide layer.
The material of the cap layer is not particularly limited as long as it can exhibit the above functions, but specifically, preferred examples include CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O ₃ , and Zr ₂ O. ₃ , Ho ₂ O ₃ , Nd ₂ O _{3 and the} like. When the material of the cap layer is CeO ₂ , the cap layer may contain a Ce—M—O-based oxide in which part of Ce is substituted with another metal atom or metal ion.

The cap layer can be formed by a PLD method (pulse laser deposition method), a sputtering method, or the like, but it is preferable to use the PLD method from the viewpoint of obtaining a high film formation rate.
As an example, forming a CeO ₂ layer as a cap layer by the PLD method can be performed in an oxygen gas atmosphere at a substrate temperature of about 500 to 1000 ° C. and about 0.6 to 100 Pa.

The thickness of the intermediate layer 12 may be appropriately adjusted according to the purpose, but is usually 0.1 to 5 μm.
When the intermediate layer 12 has a multi-layer structure in which a cap layer is laminated on the metal oxide layer, the thickness of the cap layer is usually 0.1 to 1.5 μm.

The intermediate layer 12 is formed by physical vapor deposition such as sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, ion beam assisted vapor deposition (hereinafter abbreviated as IBAD); chemical vapor deposition (CVD). ); Coating pyrolysis method (MOD method); lamination can be performed by a known method for forming an oxide thin film such as thermal spraying. In particular, the metal oxide layer formed by the IBAD method is preferable in that the crystal orientation is high and the effect of controlling the crystal orientation of the oxide superconducting layer 13 and the cap layer is high. The IBAD method is a method of orienting crystal axes by irradiating an ion beam at a predetermined angle with respect to a crystal deposition surface during deposition. Usually, an argon (Ar) ion beam is used as the ion beam. For example, the intermediate layer 12 made of Gd ₂ Zr ₂ O ₇ , MgO, or ZrO ₂ —Y ₂ O ₃ (YSZ) can reduce the value of ΔΦ (FWHM: full width at half maximum) that is an index representing the degree of orientation in the IBAD method. Therefore, it is particularly suitable.

(Oxide superconducting layer forming step S12)
Next, the oxide superconducting layer 13 is formed on the intermediate layer 12 formed in the intermediate layer forming step S11.
The oxide superconducting layer 13 can be widely applied with an oxide superconductor having a generally known composition, such as REBa ₂ Cu ₃ O _y (RE is Y, La, Nd, Sm, Er, Gd, etc. A material made of a material that represents a rare earth element, specifically, Y123 (YBa ₂ Cu ₃ O _y ) or Gd123 (GdBa ₂ Cu ₃ O _y ) can be exemplified. Further, other oxide superconductors, for _{example, Bi 2 Sr 2 Ca n-} 1 Cu n for _{O 4 + 2n + δ} becomes may be used in compositions such as those made of other oxide superconductors having high critical temperatures representative Of course.
The oxide superconducting layer 13 is laminated by physical vapor deposition such as sputtering, vacuum vapor deposition, laser vapor deposition, or electron beam vapor deposition; chemical vapor deposition (CVD); coating pyrolysis (MOD). Of these, laser vapor deposition is preferred.
The oxide superconducting layer 13 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

(Stabilization layer forming step S13)
Next, the stabilization layer 14 is formed on the oxide superconducting layer 13 formed in the stabilization layer forming step S13.
The stabilization layer 14 functions as a bypass path for current from the oxide superconducting layer 13 when a partial region of the oxide superconducting layer 13 attempts to transition to the normal conducting state.
The stabilizing layer 14 is preferably made of a metal having good conductivity, and specifically, can be exemplified by silver, a silver alloy, copper or the like. The stabilization layer 14 may have a single layer structure or a laminated structure of two or more layers. The thickness of the stabilization layer 14 can be in the range of 3 to 300 μm.

The stabilization layer 14 may have a two-layer structure of a first stabilization layer formed on the oxide superconducting layer 13 side and a second stabilization layer formed on the first stabilization layer. preferable.
In this case, the first stabilization layer formed on the oxide superconducting layer 13 side is preferably a layer made of a metal material having good conductivity such as Ag and low contact resistance with the oxide superconducting layer 13. .
In order to form the first stabilizing layer of Ag, film formation methods such as sputtering, vacuum deposition, laser deposition, electron beam deposition, physical vapor deposition, and chemical vapor deposition (CVD) are used. Adopted, the thickness can be formed to about 1 to 30 μm.

The second stabilization layer formed on the first stabilization layer is provided for stabilizing the oxide superconducting layer 13 and prevents the oxide superconducting layer 13 from transitioning to the normal conducting state. Therefore, it is preferably formed from a highly conductive metal material such as Cu, Al, or an alloy thereof. In addition, when applying the oxide superconducting wire 10 for the purpose of a current limiting device or the like, it is preferable to use a high resistance material as the second stabilization layer, so that it has high resistance to Cu, Ag, Al, such as NiCr It can be composed of a metal material.
The second stabilization layer is formed to a thickness of about 10 to 300 μm. In that case, it can be formed on the first stabilization layer using a soldering or conductive adhesive bonding method or a plating method.
Through the above steps, a superconducting laminate in which the intermediate layer 12, the oxide superconducting layer 13, and the stabilizing layer 14 are sequentially laminated on the substrate 11 can be produced.

As described above, the intermediate layer 12, the oxide superconducting layer 13, and the Ag stabilizing layer 14 laminated on one surface side of the substrate 11 are all formed by a film forming method such as a sputtering method or a PLD method. Usually, when producing a long oxide superconducting wire, a long tape-like base material 11 is wound around one reel, its winding end is pulled out and placed on the other reel, While the base material 11 is fed to the other reel, each layer is formed by a reel-to-reel method in which film formation is performed on the surface side of the base material 11.
FIG. 3 shows an example of a pulse laser deposition apparatus (PLD apparatus) that can be used for forming the cap layer constituting the intermediate layer 12 or the oxide superconducting layer 13.

The PLD apparatus A in this example includes a decompression vessel 51 connected to a decompression device 50 such as a vacuum pump, and a target 52 installed in the interior of the PLD device A includes a laser beam irradiation device 53 installed outside the decompression vessel 51. It is configured to be able to irradiate a pulsed laser beam. Further, inside the decompression container 51, a delivery reel 55, a take-up reel 56, and turning conveyance reels 57, 58 are installed at an intermediate position between them, and the substrate 11 passes from the sending reel 55 via the turning conveyance reels 57, 58. Can be moved to the take-up reel 56 side, and the surface of the substrate 11 is passed by passing the substrate 11 through the film-forming region 54 where particles (vapor deposition particles) generated from the target 52 fly during this movement. It is configured so that particles can be deposited on the side to form a film.
Although the turning conveyance reels 57 and 58 are omitted in FIG. 3, a plurality of the same configurations are arranged in the thickness direction in FIG. 3 (for example, five rows), and the substrate 11 is composed of a plurality of turning conveyance reels. It is configured to finally reach the take-up reel 56 while turning between 57 and 58 a plurality of times. Further, a heater device 60 including a heater 59 for heating the base material 11 that is turned a plurality of times between the turning conveyance reels 57 and 58 to a target film forming temperature is provided between the turning conveyance reels 57 and 58. ing.

As shown in FIG. 3, when each layer is formed on one side of the long base material 11, the base material 11 is wound by a reel in a state where a predetermined tension is applied. 11 is swelled or stressed. Of course, since it is necessary to form a plurality of layers on the base material 1 as described above, the undulation and the residue of the base material 11 tend to increase in the film forming process of each layer.
3 forms the film while heating the base material 11 to a temperature suitable for the film formation temperature of the cap layer or the oxide superconducting layer 13 constituting the intermediate layer 12. Although the film formation temperature of the cap layer or the oxide superconducting layer varies depending on the film type, it is a normal one in the range of 500 to 900 ° C. and extremely high temperature. While moving to the side, a thermal history between room temperature and 900 ° C. is received a plurality of times. Of course, when the cap layer is formed by one PLD device and the oxide superconducting layer 13 is formed by another PLD device, the thermal history received by the substrate 11 reaches a considerable number.

  Thus, the base material 11 is repeatedly subjected to stress and thermal history in the film forming process of the intermediate layer 12 and the oxide superconducting layer 13. For this reason, the substrate 11 after the formation of each layer is often in a state where waviness or residual stress is generated. According to the study of the present inventor, when the substrate 11 has waviness or residual stress, variations in superconducting characteristics tend to occur in the longitudinal direction of the oxide superconducting wire. This is because the stress applied to the oxide superconducting layer 13 is distributed in the longitudinal direction of the wire due to the undulation of the base material 11. When tensile stress is applied to the oxide superconducting layer 13, there is a strong possibility that defects such as microcracks will be introduced into the oxide superconducting layer 13, and by introducing these defects, the critical current density of the oxide superconducting layer 13 is significantly reduced. This is because there is little possibility of introducing the defects when compressive stress is applied to the oxide superconducting layer 13.

  Therefore, in the present invention, after producing a superconducting laminate in which the intermediate layer 12, the oxide superconducting layer 13 and the stabilizing layer 14 are laminated on the base material 11 in the first step S10, the base is formed in the second step S20. The back surface side of the material 11 is polished to reduce the undulation generated in the base material 11 and to reduce the residual stress (strain) in the base material 11.

[Second step S20]
(Polishing the back surface of the substrate S21)
In the polishing step S21, the back surface 11A of the substrate 11 of the superconducting laminate produced in the first step S10 (the surface on the side where the intermediate layer 12 or the oxide superconductor layer 13 of the substrate 11 is not laminated) is polished. It polishes by processing and makes the thickness of the base material 11 thin.
The polishing in the polishing step S21 is preferably performed until the undulation of the back surface 11A of the substrate 11 is equal to or less than the maximum peak height Wp of 0.2 μm of the undulation curve defined in JIS B0601-2001. By polishing the back surface 11A of the base material 11 to reduce the waviness of the base material 11, the residual stress (strain) in the base material 11 is relaxed, the stress distribution in the oxide superconducting wire is reduced, and the length of the wire Variations in superconducting characteristics in the direction can be reduced.

A method for polishing the back surface 11A of the base material 11 is not particularly limited, and examples thereof include a method for polishing by adjusting a polishing sheet used by a mechanical polishing method or a count of an abrasive.
The polishing in the polishing step S21 can alleviate the undulation and residual stress of the base material 11 by polishing until the thickness of the base material 11 is reduced to about 10 μm. The amount of change in thickness of the substrate 11 before and after polishing is not particularly limited, but can be about 10 to 200 μm. The thickness of the substrate 11 after polishing is not particularly limited and can be adjusted as appropriate, but is preferably in the range of 10 to 75 μm. By setting the thickness of the base material 11 after polishing to 10 μm or more, the strength as the base material 11 is ensured and the handleability is also improved. Moreover, the oxide superconducting wire 10 can be thinned by setting the thickness of the substrate 11 after polishing to 75 μm or less, and handling when the oxide superconducting wire 10 is processed to produce a superconducting coil or the like. Improves.
Through the above steps, the oxide superconducting wire shown in FIG. 1 can be manufactured.

  According to the method for manufacturing an oxide superconducting wire of the present invention, a superconducting laminate in which an intermediate layer 12, an oxide superconducting layer 13 and a stabilizing layer 14 are laminated on the surface side of a substrate 11 is prepared, and this superconducting laminate is prepared. By polishing the back surface 11 </ b> A of the base material 11, the undulation inherent in the base material 11 and the undulation generated in the base material 11 by the film forming process of each layer on the base material 11 are reduced, and the residual of the base material 11 Stress (strain) can be relaxed. Therefore, the stress distribution in the longitudinal direction of the substrate 11 is reduced, the stress applied to the oxide superconducting layer 13 is small, and is uniformized in the longitudinal direction of the wire, so that the dispersion of the superconducting characteristics in the longitudinal direction of the wire is small. The oxide superconducting wire 10 can be manufactured.

In addition, when a thin oxide superconducting wire is produced by a conventional method, if each layer is formed using a thinner substrate than usual, the tension or temperature is applied to the substrate in the film forming process. There has been a problem that it is difficult to form an oxide superconducting layer with good crystal orientation and the properties of the oxide superconducting wire to be manufactured are lowered. In this case, it is necessary to optimize the film forming conditions and improve the film forming apparatus, and it has been necessary to study each time the thickness of the base material is changed.
On the other hand, the manufacturing method of the oxide superconducting wire according to the present invention produces a superconducting laminate after laminating the intermediate layer 12, the oxide superconducting layer 13 and the stabilizing layer 14 on the surface side of the substrate 11. In this configuration, the back surface 11A of the substrate 11 of the superconducting laminate is polished to reduce the thickness of the substrate 11. Therefore, since each layer can be formed under the optimized conditions using the base material 11 having a normal thickness, the oxide superconducting layer 13 with good crystal orientation can be formed, and the base is maintained while maintaining the crystal orientation. Since the material 11 can be polished and thinned, a thin oxide superconducting wire having good characteristics can be manufactured.

  As mentioned above, although embodiment of the manufacturing method of the oxide superconducting wire of this invention was described, in the said embodiment, each part of an oxide superconducting wire is an example, and it changes suitably in the range which does not deviate from the scope of the present invention. Is possible.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.

Example 1
A film of Al ₂ O ₃ (diffusion prevention layer; film thickness 150 nm) formed by sputtering on a tape-shaped Hastelloy (trade name, manufactured by Haynes, USA) having a thickness of 100 μm, a width of 10 mm, and a total length of 100 m. Then, Y ₂ O ₃ (bed layer; film thickness: 20 nm) was formed by ion beam sputtering. Next, MgO (intermediate layer; film thickness: 10 nm) was formed on the bed layer by ion beam assisted vapor deposition (IBAD method), and then 0.5 μm thick CeO ₂ (PLD method) was formed by pulse laser vapor deposition (PLD method). (Cap layer) was formed. Next, a 1.0 μm thick GdBa ₂ Cu ₃ O ₇ (oxide superconducting layer) is formed on the CeO ₂ layer by a PLD method at a film forming temperature of 900 ° C., and further a 7 μm thick silver is formed on the oxide superconducting layer by a sputtering method. A superconducting laminate was produced by forming a layer (stabilization layer).
In forming the Al ₂ O ₃ layer, the Y ₂ O ₃ layer, the MgO layer, the CeO ₂ layer, the GdBa ₂ Cu ₃ O ₇ layer, and the silver layer, the tape-shaped substrate is placed inside the film forming apparatus. Each layer was formed over the entire length of the tape-shaped substrate so that it was wound around a reel and formed into a film while being fed from one reel to the other.

Next, using emery paper or a grindstone, the counts were changed in order from No. 100 to 1500, and the back surface of the base material of the superconducting laminate produced above (on the side where no intermediate layer or oxide superconducting layer was formed) Surface). The thickness of the substrate after polishing was 92 μm. Then, the thickness of the base material was set to 75 μm by further polishing using an alumina paste having a particle size of 2 μm.
In addition, grinding | polishing in each grinding | polishing process was performed by pressing an abrasives on the back surface of a base material, applying a 1000-g load.
An oxide superconducting wire was produced by the above process.
Terminals for measurement were attached to both ends in the longitudinal direction of the obtained oxide superconducting wire, and the superconducting characteristics at 77 K and 0 T were measured over the entire length of the wire. The critical current density Jc was 3.5 MA / cm ^2. It was.

(Comparative Example 1)
An oxide superconducting wire was produced in the same manner as in Example 1 except that the back surface of the substrate was not polished. Terminals for measurement were attached to both ends of the obtained oxide superconducting wire in the longitudinal direction, and the superconducting characteristics at 77 K and 0 T were measured over the entire length of the wire, and the critical current density Jc was 3.6 MA / cm ^2. It was.

  From the above results, the critical current densities of the oxide superconducting wires of Example 1 and Comparative Example 1 are substantially the same, and after forming the intermediate layer, oxide superconducting layer, and stabilizing layer on the surface of the base material, Even if the back surface of the material was polished, it was found that the superconducting characteristics were not deteriorated by this polishing process. Therefore, according to this invention, it has confirmed that the oxide superconducting wire which is thin and had a favorable superconducting characteristic can be manufactured.

Moreover, about the oxide superconducting wire of Example 1 and Comparative Example 1, the surface property of the back surface of the substrate was measured using Surface Profilometer XP-100 manufactured by Ambios Technology. The result is shown in FIG. In FIG. 4, the vertical axis represents the relative height when the average height of the back surface of the base material is “0”.
Further, for the oxide superconducting wires of Example 1 and Comparative Example 1, the distribution of critical current density Ic in the longitudinal direction of the wire at 77K was measured using TAPESTAR manufactured by THEVA. The result is shown in FIG. In FIG. 5, the horizontal axis indicates the measurement position in the longitudinal direction of the wire.

From the results of FIG. 4, the base material of the oxide superconducting wire of Example 1 has a maximum peak height Wp = 0.15 μm of the undulation curve, and the base material of the oxide superconducting wire of Comparative Example 1 (Wp = 1.0 μm). ) The swell was much smaller.
From the results of FIG. 5, the oxide superconducting wire of Example 1 showed less variation in critical current density in the longitudinal direction of the wire than the oxide superconducting wire of Comparative Example 1.
From the above results, in Example 1 according to the present invention, after forming the intermediate layer or the oxide superconducting layer on the surface of the base material, the back surface of the base material is polished, whereby the longitudinal undulation of the base material is obtained. It has been confirmed that the residual stress in the substrate is reduced and the variation in the longitudinal characteristics of the oxide superconducting wire can be reduced.

  The present invention can be used for oxide superconducting wires used in various superconducting devices such as superconducting motors and current limiters.

  DESCRIPTION OF SYMBOLS 10 ... Oxide superconducting wire, 11 ... Base material, 11A ... Back surface of base material, 12 ... Intermediate layer, 13 ... Oxide superconducting layer, 14 ... Stabilization layer, 50 ... Decompression device, 51 ... Decompression vessel, 52 ... Target 53 ... Irradiation device, 54 ... Film formation region, 55 ... Sending reel, 56 ... Take-up reel, 57, 58 ... Turning conveyance reel, 59 ... Heater, 60 ... Heater device, A ... PLD device.

Claims (2)

A first step of preparing a superconducting laminate in which an intermediate layer, an oxide superconducting layer, and a stabilizing layer are laminated in this order on the surface of a tape-shaped substrate;
A second step of polishing the back surface of the base material of the superconducting laminate to reduce the thickness of the base material;
A method for producing an oxide superconducting wire characterized by comprising: In the first step,
The tape-shaped base material is wound around a delivery reel, the winding end portion of the base material wound around the delivery reel is pulled out and installed on the take-up reel,
Forming a deposition region where vapor deposition particles fly between the delivery reel and the take-up reel;
By feeding the base material from the delivery reel to the take-up reel, passing the base material through the film formation region and depositing the vapor deposition particles on the base material,
2. The method of manufacturing an oxide superconducting wire according to claim 1, wherein at least one of the intermediate layer, the oxide superconducting layer, and the stabilizing layer is formed.

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