JP6167443B2 - Superconducting wire and manufacturing method thereof - Google Patents

Description

  The present invention relates to a superconducting wire and a method for manufacturing the same.

Conventionally, a superconducting wire including an alignment layer is known (see, for example, Patent Documents 1 and 2). In this conventional superconducting wire, the alignment layer is an intermediate layer between the metal substrate and the superconducting layer, and is formed by an ion beam assisted deposition (IBAD) process.
In practice, an additional simple oxide layer is formed under the alignment layer and between the alignment layer and the superconducting layer to prevent chemical interaction of the alignment layer with the substrate and the superconducting layer during the heat treatment. May be.

The IBAD method is a technique that forms an oriented ceramic film on non-oriented metal tape or oxide-coated tape by sputtering Ar ⁺ ions on the tape at a specific angle during film deposition. Yes (see, for example, Patent Document 2). Deposition is performed on the amorphous oxide seed layer.

JP 2012-181963 A JP 2012-104444 A

  One of the objects of the present invention is to provide a superconducting wire that can be manufactured at a low cost by a simple process, and a manufacturing method thereof.

[1] In order to achieve the above object, the present invention provides a substrate, a first layer formed on the substrate, an alignment layer formed directly on the first layer, and the alignment layer. A superconducting wire is provided, which includes a second layer that is formed directly on the main layer and is composed mainly of the same material as the material of the first layer, and a superconducting layer formed on the second layer.

[2] In the superconducting wire of [1], the alignment layer is formed by an ion beam assisted deposition process.

[3] In the superconducting wire of [2] above, the first layer is crystalline before the ion beam assisted deposition step.

[4] In the superconducting wire according to any one of [1] to [3], the first layer and the second layer may contain a perovskite material.

[5] In the superconducting wire of [4], the perovskite material may be selected from the group consisting of LaMnO ₃ , LaGaO ₃ , LaCrO ₃ , LaAlO ₃ , SrTiO ₃ , and SrRuO ₃ .

[6] In the superconducting wire according to any one of [1] to [5], the alignment layer may include MgO.

[7] In the superconducting wire according to any one of [1] to [6], the superconducting wire includes CeO ₂ doped with a rare earth element, and is formed directly under the superconducting layer. A layer may further be included.

[8] In any one of the above [1] to [7], the superconducting wire may further include a buffer layer formed between the substrate and the first layer.

[9] In the superconducting wire of [8], the buffer layer contains Y ₂ O ₃ , CeO ₂ , Al ₂ O ₃ , or Al _x O.

[10] In the superconducting wire according to any one of [1] to [9], the second layer is under a pressure and a temperature that are the same as the deposition pressure and temperature for forming the first layer. It may be formed by deposition.

[11] In order to achieve the above object, the present invention provides a method for forming a first layer by forming a first layer on a substrate, forming an alignment layer directly on the first layer, and forming the first layer. A second layer is directly formed on the alignment layer under the same pressure and temperature as the pressure and temperature, and the second layer is mainly composed of the same material as that of the first layer, and the second layer Forming a superconducting layer on the other layer. A method of manufacturing a superconducting wire is provided.

[12] In the method of manufacturing a superconducting wire according to [11], the first layer and the second layer may be continuously formed in the same deposition chamber.

[13] In the method of manufacturing a superconducting wire according to [11] or [12], the alignment layer may be formed by an ion beam assisted deposition process.

[14] In the method of manufacturing a superconducting wire according to [13], the first layer is crystalline before the ion beam assisted deposition step.

  ADVANTAGE OF THE INVENTION According to this invention, the superconducting wire which can be manufactured at low cost by a simple process, and its manufacturing method can be provided.

FIG. 1 is a perspective view of a superconducting wire according to the first embodiment of the present invention. FIG. 2 is a sectional view of the superconducting wire of FIG. 1 according to the first embodiment of the present invention. FIG. 3 is a flowchart showing a manufacturing process of the superconducting wire according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view of a superconducting wire according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view of a superconducting wire according to the third embodiment of the present invention.

(First embodiment of the present invention)
(Configuration of superconducting wire)
FIG. 1 is a perspective view of the superconducting wire 1. FIG. 2 is a cross-sectional view of the superconducting wire 1. The superconducting wire 1 includes a substrate 10, a first layer 11 formed on the substrate 10, an alignment layer 12 directly formed on the first layer 11, and a second layer directly formed on the alignment layer 12. Layer 13, superconducting layer 14 formed on second layer 13, and protective layer 15 formed on superconducting layer 14.

  The substrate 10 is a tape-shaped substrate and includes a metal or a metal alloy such as Hastelloy (trademark). For example, the substrate 10 has a thickness of 50 to 100 μm.

The first layer 11 preferably comprises a perovskite material such as LaMnO ₃ , LaGaO ₃ , LaCrO ₃ , LaAlO ₃ , SrTiO ₃ , or SrRuO ₃ . These perovskite materials may be pure or may be doped in the A site and B site of the perovskite structure of the general formula ABO ₃ . The first layer 11 may be a perovskite material in which a doping element is doped in the A site and the B site. Doping elements include Mg, Ca, Sr, or Ba for the A site and Mg, Nb, Ta, Zr, or Hf for the B site. When the first layer 11 includes a perovskite material, the alignment layer 12 includes MgO.

  The first layer 11 can function as a diffusion barrier layer that suppresses diffusion of metal from the substrate 10 to the alignment layer 12. For example, when the substrate 10 includes hastelloy, the first layer 11 can suppress diffusion of Ni in the substrate 10 into the alignment layer 12.

  The first layer 11 can function as an adhesion layer for increasing the adhesion between the substrate 10 and the alignment layer 12. High-temperature treatment at a temperature of, for example, 600 ° C. or higher in the deposition process improves the adhesive strength of the first layer 11. The first layer 11 has a thickness of 20 to 50 nm, for example.

  The alignment layer 12 has a biaxial alignment structure. The alignment layer 12 is an alignment layer formed by an ion beam assisted deposition (IBAD) process. The alignment layer 12 includes MgO or the like. The alignment layer 12 may be MgO doped with Ca or Sr, for example. The alignment layer 12 may have a stacked structure including a first MgO layer formed by the IBAD process and a second MgO layer epitaxially grown on the first MgO layer. The alignment layer 12 has a thickness of 5 to 20 nm, for example.

  The second layer 13 is mainly composed of the same material as that of the first layer 11. When the second layer 13 includes a perovskite material, the second layer 13 is generated by lattice matching on the alignment layer 12 including MgO.

  The second layer 13 can function as a cap layer that suppresses a chemical reaction between the alignment layer 12 and the superconducting layer 14. In addition, the second layer 13 improves lattice matching for the epitaxial growth of the superconducting layer 14. The second layer 13 has a thickness of 20 to 50 nm, for example.

The superconducting layer 14 preferably includes a high temperature superconductor such as REBa ₂ Cu ₃ O _{6 + x} (RE is a rare earth element such as Y, Sm, Eu, or Gd). The superconducting layer 14 more preferably includes YBa ₂ Cu ₃ O _{6 + x} , GdBa ₂ Cu ₃ O _{6 + x} , or a combination thereof. The superconducting layer 14 may include non-conductive nanoparticles in order to improve superconducting properties in a magnetic field. The superconducting layer 14 has a thickness of 1 to 3 μm, for example.

  The protective layer 15 protects the superconducting layer 14. The protective layer 15 contains Ag or the like. The protective layer 15 has a thickness of 0.5 to 2.0 μm, for example.

(Manufacture of superconducting wires)
Below, the example of the manufacturing process of the superconducting wire 1 is described.

  FIG. 3 is a flowchart showing the manufacturing process of the superconducting wire 1.

  First, the first layer 11 is formed on the substrate 10 by the RF-magnetron sputtering method or the pulse laser deposition (PLD) method (step S1). The first layer 11 is formed at a temperature equal to or higher than its crystallization temperature (for example, 600 ° C.). Accordingly, the first layer 11 is crystalline before the IBAD process for forming the alignment layer 12.

  Next, the alignment layer 12 is formed on the first layer 11 by the IBAD process (step S2). Since the first layer 11 is crystalline and is subjected to heat treatment under the same conditions as the deposition of the cap layer, the alignment layer 12 includes the epitaxial layer of the alignment layer 12 having a stacked structure and the second layer 13. No significant distortion during the deposition of Therefore, since the alignment layer 12 is formed on the first layer 11 that is already crystalline, a high degree of alignment is maintained.

  Next, the second layer 13 is formed on the alignment layer 12 by RF-magnetron sputtering method or PLD method (step S3). The second layer 13 is formed under the same pressure (0.2 to 1.0 Pa) and temperature (600 to 950 ° C.) as the pressure and temperature for forming the first layer 11. Further, the first layer 11 and the second layer 13 are continuously formed in the same deposition chamber. Therefore, the manufacturing process of the superconducting wire 1 can be simplified, and the manufacturing cost can be reduced.

  Next, the superconducting layer 14 is formed on the second layer 13 by the PLD method. Further, oxygen can be introduced into the superconducting layer 14 by oxygen annealing. The oxygen annealing step and the oxygen concentration in the superconducting layer 14 are important for the superconducting characteristics such as the critical temperature and critical current of the superconducting layer 14.

Next, the protective layer 15 is formed on the superconducting layer 14 by DC magnetron sputtering. If necessary, the protective layer 15 can be formed thicker by an electrochemical deposition (electroplating) process from an aqueous AgNO ₃ solution. The electroplating process can be performed before or after the oxygen annealing process of the superconducting layer 14.

(Second embodiment of the present invention)
The second embodiment is different from the first embodiment in that a buffer layer is formed between the substrate 10 and the first layer 11. Note that the description of the same points as in the first embodiment is omitted or simplified.

(Configuration of superconducting wire)
FIG. 4 is a cross-sectional view of the superconducting wire 2. The superconducting wire 2 includes a substrate 10, a buffer layer 20 formed on the substrate 10, a first layer 11 formed on the buffer layer 20, and an alignment layer 12 formed directly on the first layer 11. And a second layer 13 formed directly on the alignment layer 12, a superconducting layer 14 formed on the second layer 13, and a protective layer 15 formed on the superconducting layer 14.

The buffer layer 20 is a buffer layer between the substrate 10 and the first layer 11. The buffer layer 20 includes Al ₂ O ₃ , Al _x O, Y ₂ O ₃ , CeO ₂ or the like. Here, Al _x O is aluminum-rich alumina and can be deposited by reactive RF or DC magnetron sputtering in an oxygen-deficient atmosphere. When the buffer layer 20 is Al _x O, the Al metal improves the surface roughness of the first layer 11 during the deposition of the first layer 11 at high temperature. The buffer layer 20 has a thickness of 20 to 100 nm, for example.

  The buffer layer 20 is formed by, for example, physical vapor deposition or solution deposition. The buffer layer 20 should react slowly with the substrate 10 so that the buffer layer 20 adheres to the surface of the substrate 10. If the reaction is strong, the metal from the alloy introduced by the reaction will contaminate the other layers.

(Third embodiment of the present invention)
The third embodiment is different from the second embodiment in that the third layer is formed between the second layer 13 and the superconducting layer 14. Note that the description of the same points as in the first embodiment and the second embodiment will be omitted or simplified.

(Configuration of superconducting wire)
FIG. 5 is a cross-sectional view of the superconducting wire 3. The superconducting wire 3 includes a substrate 10, a buffer layer 20 formed on the substrate 10, a first layer 11 formed on the buffer layer 20, and an alignment layer 12 formed directly on the first layer 11. A second layer 13 formed directly on the alignment layer 12, a third layer 30 formed on the second layer 13, a superconducting layer 14 formed directly on the third layer 30, And a protective layer 15 formed on the superconducting layer 14.

The third layer 30 is a buffer layer between the second layer 13 and the superconducting layer 14. The third layer 30 includes, for example, CeO ₂ doped with rare earth elements to improve the orientation of the third layer 30 and to promote oxygen diffusion during the oxygen annealing process. When oxygen ions in the third layer 30 diffuse into the superconducting layer 14, the same concentration of oxygen in the superconducting layer 14 and its uniform distribution is achieved in a shorter time.

When the third layer 30 includes CeO ₂ , the third layer 30 is generated by lattice matching on the second layer 13 including the perovskite material. The third layer 30 has a thickness of 150 to 500 nm, for example. The third layer 30 is formed by, for example, a PLD method or RF magnetron sputtering.

  Further, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention or the changing technology. Although the invention has been described with reference to specific embodiments and examples for a complete and clear disclosure, the appended claims are not limited thereto and those skilled in the art within the scope of the disclosure herein. It is interpreted as embodying all possible changes and alternative structures.

  ADVANTAGE OF THE INVENTION According to this invention, the superconducting wire which can be manufactured by a simple process with low cost, and the manufacturing method of the superconducting wire can be provided.

DESCRIPTION OF SYMBOLS 1 Superconducting wire 2 Superconducting wire 3 Superconducting wire 10 Substrate 11 1st layer 12 Orientation layer 13 2nd layer 14 Superconducting layer 15 Protective layer 20 Buffer layer 30 3rd layer

Claims (10)

A substrate,
A first layer formed on the substrate;
An alignment layer formed directly on the first layer by an ion beam assisted deposition process ;
A second layer that is formed directly on the alignment layer and is composed mainly of the same material as that of the first layer;
A superconducting layer formed on the second layer;
Only including,
A superconducting wire wherein the first layer is crystalline prior to the ion beam assisted deposition process . The first layer and the second layer comprise a perovskite material;
The superconducting wire according to claim 1 . The perovskite material is selected from the group consisting of LaMnO ₃ , LaGaO ₃ , LaCrO ₃ , LaAlO ₃ , SrTiO ₃ , and SrRuO ₃ ;
The superconducting wire according to claim 2 . The alignment layer includes MgO;
The superconducting wire according to any one of claims 1 to 3 . A CeO ₂ doped with a rare earth element, further comprising a third layer formed directly under the superconducting layer;
The superconducting wire according to any one of claims 1 to 4 . A buffer layer formed between the substrate and the first layer;
The superconducting wire according to any one of claims 1 to 5 . The buffer layer includes Y ₂ O ₃ , CeO ₂ , Al ₂ O ₃ , or Al _x O;
The superconducting wire according to claim 6 . The second layer is formed by deposition under the same pressure and temperature as the deposition pressure and temperature to form the first layer;
The superconducting wire according to any one of claims 1 to 7 . Forming a first layer on the substrate;
An alignment layer is directly formed on the first layer by an ion beam assisted deposition process ,
A second layer is formed directly on the alignment layer under the same pressure and temperature as the pressure and temperature for forming the first layer, and the second layer is formed of the material of the first layer. The same material as the main component,
Forming a superconducting layer on the second layer;
Look at including it,
A method of manufacturing a superconducting wire, wherein the first layer is crystalline before the ion beam assisted deposition step . The first layer and the second layer are formed sequentially in the same deposition chamber;
A method for manufacturing a superconducting wire according to claim 9 .

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