JP2014220257A - Method of producing oxide superconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of an oxide superconductor which enables improvement of orientation.SOLUTION: A method of producing an oxide superconductor includes a step of forming oriented parts on a substrate and bringing a solution containing a metal trifluoroacetate salt into contact with oriented parts and parts other than the oriented parts to form a gel film containing the metal and the fluoride contained in the metal trifluoroacetate salt on the substrate and a step of heat-treating the substrate to form an oriented superconductive layer, with the oriented parts and either of the crystal axes oriented, on the oriented parts and the parts other than the oriented parts.

Description

  Embodiments described herein relate generally to a method for manufacturing an oxide superconductor.

  The technique of forming an oriented oxide thin film on a metal tape is the most advanced technique in the second generation superconductor. In most cases of thin film deposition techniques related to semiconductors and hard disks, the deposition temperature is generally as low as 400 ° C. or lower. Therefore, for example, in film formation by sputtering, the flying particles are not given enough energy to bond with other particles at the atomic level when landing on the substrate. Therefore, in technical fields such as semiconductors, there is little discussion about the degree of in-plane orientation, which is an index of oriented texture.

  On the other hand, in an yttrium-based (including lanthanoid group) oxide superconductor film forming technique formed at about 800 ° C., the oxide layer after film formation needs to be oriented at the atomic level. Therefore, the film forming temperature is as high as 600 to 800 ° C., and is a technical field for discussing the in-plane orientation degree. At present, the field of oxide superconductors requires the highest degree of orientation in thin film technology.

Japanese Patent No. 2996568 Japanese Patent No. 3556586 US Pat. No. 7,071,149 US Pat. No. 6,756,139 US Pat. No. 7,071,149 US Patent No. 2007-238619 Takeshi Araki and Izumi Hirabayashi, Supercond. Sci. Technol. 16 (2003) R71 Yasuhiro Iijima, et al., IEEE Trans. On Appl. Supercond. 11 (2001) 3457 Y.-Y.Xie et al. Physica C 426-431 (2005) 849 S.I.Kim, et al., Supercond. Sci. Technol. 19 (2006) 968 D.T.Verebelyi, et al., Appl. Phys. Lett. 76 (2000) 1755

  Embodiments of the present invention provide a method for manufacturing an oxide superconductor capable of improving the orientation.

  In the method of manufacturing an oxide superconductor according to the embodiment, an orientation part is formed on a base, a solution containing a metal trifluoroacetate is brought into contact with the orientation part and a part other than the orientation part, and the lower part is formed. Forming a gel film containing a metal and a fluoride contained in the metal trifluoroacetate on the ground, heat-treating the base, and aligning the alignment portion on the alignment portion and a portion other than the alignment portion; Forming an oriented superconducting layer in which the crystal axes are oriented.

(A) is sectional drawing which illustrates the oxide superconductor which concerns on 1st Embodiment, (b) is the oxide superconductor which concerns on 1st Embodiment, AA shown to (a) It is the schematic diagram which synthesize | combined the cross section shown to a 'line and a BB' line. (A)-(d) is process sectional drawing which illustrates the manufacturing method of the oxide superconductor which concerns on 1st Embodiment, (e) is manufacture of the oxide superconductor which concerns on 1st Embodiment. It is process top view of a method. It is a flowchart figure which illustrates the formation method of a coating solution in the manufacturing method of the oxide superconductor film | membrane which concerns on 1st Embodiment. It is a flowchart figure which illustrates TFA-MOD method in the manufacturing method of the oxide superconductor which concerns on 1st Embodiment. It is a schematic diagram which illustrates the manufacturing method of the oxide superconductor which concerns on 1st Embodiment. In the manufacturing method of the oxide superconductor concerning a 1st embodiment, it is a graph which illustrates the temperature profile in calcination, a vertical axis shows temperature and a horizontal axis shows time. In the manufacturing method of the oxide superconductor which concerns on 1st Embodiment, it is a graph which illustrates the temperature profile in this baking, a vertical axis | shaft shows temperature and a horizontal axis shows time. It is sectional drawing which illustrates the oxide superconductor which concerns on 2nd Embodiment. It is process sectional drawing which illustrates the manufacturing method of the oxide superconductor which concerns on 2nd Embodiment. (A) is a polar figure measured by the thin film X-ray diffraction method in the oriented superconducting layer, (b) is a schematic plan view illustrating the crystal structure of the oriented superconducting layer, and (c) is the oriented superconducting. It is a schematic cross section which illustrates the crystal structure of a layer. It is a schematic cross section at the time of forming an oriented superconducting layer on the base material and the metal layer formed on the base material. It is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position of 5 μm from the Pt film formation interface. It is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position of 10 μm from the Pt film formation interface. It is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position 20 μm from the Pt film formation interface. It is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position 40 μm from the Pt film formation interface.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, the first embodiment will be described.

  FIG. 1A is a cross-sectional view illustrating an oxide superconductor according to the first embodiment, and FIG. 1B is a cross-sectional view of the oxide superconductor according to the first embodiment. It is the schematic diagram which synthesize | combined the cross section shown to -A 'line and BB' line.

As shown in FIGS. 1A and 1B, the oxide superconductor 1 according to this embodiment includes a base material 11, a diffusion prevention layer 12, and a plurality of orientation sources 13 (lattice match with the upper oxide 15. An oxide having a large aspect ratio), an unoriented layer 14 and an oriented superconducting layer 15 are provided.
The base material 11 is a tape containing stainless steel (SUS), for example. The upper surface of the substrate 11 is smooth, for example.
The diffusion preventing layer 12 is disposed on the base material 11. The diffusion prevention layer 12 is an oxide layer of a predetermined material, for example. The diffusion prevention layer 12 prevents, for example, nickel (Ni) contained in stainless steel from diffusing into the oriented superconducting layer 15 formed on the substrate 11.

  A plurality of orientation sources 13 are disposed on the diffusion preventing layer 12. The orientation origin 13 is, for example, a ceramic fiber containing an oxide. The shape of the orientation origin 13 is a shape extending in one direction. The length in the extending direction of the orientation origin 13 is, for example, 10 to 200 micrometers (μm). The longer the length, the better. However, even if it is 0.1 micrometer, it is sufficient if it can be oriented in the sheet. The cross section orthogonal to the extending direction in the orientation origin 13 has a width of 10 to 100 nanometers (nm) and a thickness of 1 to 10 nanometers (nm). The aspect ratio of width to thickness is often 1: 5 to 1:30. Each orientation source 13 is distributed on the upper surface of the diffusion prevention layer 12 with the extending direction oriented. The in-plane orientation degree (Δφ) of the major axis of each orientation source 13 is within 10 degrees, preferably within 2 degrees. Δφ indicates a statistical distribution in the in-plane distribution of orientation directions, and is an index generally used in the superconducting field. The value can be measured by polar figure measurement.

The non-oriented layer 14 is formed so as to embed between the orientation sources 13 on the diffusion preventing layer 12. The upper surface of the non-oriented layer 14 is preferably located at the same height as the upper surface of the orientation source 13 or may be located lower than the upper surface of the orientation source 13. Even if the upper surface of the non-oriented layer 14 is higher than the upper surface of the orientation origin 13, the alignment layer can propagate.
The oriented superconducting layer 15 is disposed on the orientation origin 13 and the non-oriented layer 14. The orientation origin 13 and the non-oriented layer 14 are provided in contact with the lower surface of the oriented superconducting layer 15. The oriented superconducting layer 15 includes a single crystal portion. The single crystal portion includes, for example, crystal axes of an a-axis 15a, a b-axis 15b, and a c-axis 15c. In the single crystal portion, the crystal axes are oriented. The direction in which the crystal axis of the single crystal portion in the oriented superconducting layer 15 is oriented is within 10 degrees, more preferably within 2 degrees.

  The a-axis 15a and the b-axis 15b are, for example, two orthogonal directions in a plane parallel to the upper surface of the orientation source 13, and a parallel root of about 2 of the lattice length of the superconductor such as CeO2. In the case of double, the direction is inclined 45 degrees in the plane. Here, the case of going straight will be described. The a-axis 15 a is, for example, the major axis direction of the orientation origin 13. Therefore, the orientation origin 13 is oriented within a swing angle of 10 degrees with respect to the a-axis of the oriented superconducting layer 15. The b-axis 15b is a direction orthogonal to the direction in which the long axis 13 originating from the alignment extends. However, since superconductors have approximately the same a-axis and b-axis lengths, replacement of them frequently occurs. The c-axis 15 c is a direction orthogonal to the upper surface of the orientation origin 13. A portion of 90% or more of the oriented superconducting layer 15 contains crystals oriented in the c-axis. The orientation origin 13 functions as an orientation origin for orienting the orientation superconducting layer 15 formed on the orientation origin 13. On the other hand, the non-oriented layer 14 is mainly a metal having a small polarity or an oxide layer having no lattice matching with the oriented superconducting layer 15. In the case of an oxide having no lattice matching, it may be oriented. This is because it has been found that the upper alignment layer is not affected. Not having lattice matching often means that the lattice constant is within 5% or that the lattice constant during 45-degree in-plane rotation is within 3%.

The oriented superconducting layer 15 includes, for example, a DyBa ₂ Cu ₃ O _7-X superconducting material. The non-oriented layer 14 may also contain the same material as the oriented superconducting layer 15, for example, a DyBa ₂ Cu ₃ O _7-X superconducting material. However, the single crystal portion of the non-oriented layer 14 is smaller than the single crystal portion of the oriented superconducting layer 15. Further, the ratio of the oriented crystals in the non-oriented layer 14 is smaller than the ratio of the oriented superconducting layer 15. Therefore, Δφ of the non-oriented layer 14 that is an oxide is larger than Δφ of the oriented superconducting layer 15. In addition, since a metal such as Pt is electrically isotropic, Δφ in measurement is a small value, but the alignment superconducting layer 15 does not form an alignment layer immediately above it. This is because, in the case where the polarity is a metal, it is small, and therefore, an oxide having a large polarity does not take a structure in which Δφ is inherited in the upper part.

The oriented superconducting layer 15 contains 2.0 × 10 ^{16 to} 5.0 × 10 ¹⁹ atoms / cc of fluorine and 1.0 × 10 ^{18 to} 5.0 × 10 ²⁰ atoms / cc of carbon. This is a residue derived from the TFA-MOD method and inevitably left by a liquid-phase calcination reaction at chemical equilibrium.
The total area SO of the area SS immediately below the portion within Δφ10 degrees in the oriented superconducting layer 15 and the area S13 of the portion in contact with the orientation origin 13 oriented at the swing angle within 10 degrees on the lower surface of the oriented superconducting layer 15. The area SO <0.3 × the area SS, that is, the area SO is 0.3 or less of the area SS. Preferably, the area SO is 0.1 or less of the area SS. In the present specification, for example, the area SS and the area SO, may represent a region _{S S} and the area _{S O.} The short side of the portion other than the region directly above the portion in contact with the alignment origin 13 in the alignment superconducting layer 15 may be about 10 nanometers or 1 micrometer or more. Since several unit cells are sufficient to function as the orientation origin, the width of the oriented superconducting layer 15 in the direction parallel to the upper surface of the non-oriented layer 14 is just above the portion in contact with the non-oriented layer 14. , 30 nanometers (nm) or more, preferably 5 micrometers (μm) or more. The oxide superconductor 1 containing oriented oxide is also a thin film of oriented oxide.

Next, a method for manufacturing the oxide superconductor 1 according to this embodiment will be described.
2A to 2D are process cross-sectional views illustrating a method for manufacturing an oxide superconductor according to the first embodiment, and FIG. 2E is an oxide superconductor according to the first embodiment. It is process top view of this manufacturing method. FIG. 2E is a plan view of FIG.
First, as shown to Fig.2 (a), the base material 11 is prepared first. The base material 11 is a tape containing stainless steel (SUS), for example.
Next, as shown in FIG. 2B, the diffusion preventing layer 12 is formed on the base material 11. The diffusion preventing layer 12 is, for example, a predetermined oxide film layer.

  Next, as shown in FIG. 2C, the orientation origin sheet 16 is disposed on the diffusion preventing layer 12. The orientation origin sheet 16 includes, for example, a binder 17 containing an organic component and a plurality of orientation origins 13. Each orientation source 13 is oriented and distributed within the binder 17. In the orientation origin sheet 16, for example, the orientation origin 13 is dispersed in a solution with a dispersing agent, and is included in the binder 17 to be thinned. Thereby, the azimuth distribution of each orientation source 13 can be set to Δφ within 10 degrees, more preferably within 2 degrees.

  Next, as shown in FIGS. 2D and 2E, the orientation origin sheet 16 is heated at a high temperature, and the binder 17 is burned and removed. As a result, the orientation origin 13 remains on the diffusion prevention layer 12 while being oriented at Δφ smaller than 2 degrees. In this way, the orientation origin 13 is disposed on the diffusion preventing layer 12. A combination of the base material 11, the diffusion prevention layer 12, and the orientation origin 13 is referred to as a base. The base includes an oriented portion, that is, an orientation origin 13 and a non-oriented portion.

  Next, an oriented superconducting layer is formed on the diffusion prevention layer 12 and 13 with a small Δφ by a TFA-MOD method (Trifluoroacetates Metal Organic Deposition) using a metal trifluoroacetate described below. . First, a coating solution used for the TFA-MOD method is prepared.

FIG. 3 is a flowchart illustrating a method for forming a coating solution in the method for manufacturing an oxide superconductor film according to the first embodiment.
As shown in step S11 of FIG. 3, powders of metal acetates such as Dy (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) _2, and Cu (OCOCH ₃ ) ₂ hydrates in ion-exchanged water, respectively. Dissolve and react with each other by mixing and stirring with equimolar amounts of trifluoroacetic acid (CF ₃ COOH). Thereby, the mixed solution mixed by the metal ion molar ratio 1: 2: 3 is formed.

Next, as shown in step S12 of FIG. 3, the obtained mixed solution is placed in an eggplant-shaped flask, and subjected to reaction and purification under reduced pressure in a rotary evaporator for 12 hours, thereby translucent blue gel or sol Form.
Next, as shown in step S13 of FIG. 3, a part of the gel or sol is dissolved in methanol to form a 1.52M coating solution in terms of metal ions. This is a coating solution that is not highly purified and contains impurities.

Next, as shown in step S14 of FIG. 3, the obtained gel or sol is completely dissolved by adding methanol corresponding to about 100 times its weight, and the solution is again subjected to reduced pressure in a rotary evaporator. Reaction and purification are carried out for 12 hours. Thereby, a translucent blue gel or sol is formed.
Next, as shown in step S15 of FIG. 3, the obtained gel or sol is dissolved in methanol and diluted by using a volumetric flask. Thereby, a coating solution of 1.52M in terms of metal ions is formed.

FIG. 4 is a flowchart illustrating the TFA-MOD method in the method for manufacturing an oxide superconductor according to the first embodiment.
FIG. 5 is a schematic view illustrating the method for manufacturing the oxide superconductor according to the first embodiment.
FIG. 6 is a graph illustrating a temperature profile in calcining in the method for manufacturing an oxide superconductor according to the first embodiment, where the vertical axis indicates temperature and the horizontal axis indicates time.
FIG. 7 is a graph illustrating a temperature profile in the firing in the method for manufacturing an oxide superconductor according to the first embodiment, where the vertical axis indicates temperature and the horizontal axis indicates time.

First, as shown in step S21 of FIG. 4, a coating solution is prepared. The coating solution is prepared by, for example, the method shown in FIG.
Next, as shown in step S22 of FIG. 4 and FIG. 5, the gel film 24 is formed on the substrate 11 by dipping in the coating solution 23 and pulling up the substrate 11 in contact with the coating solution 23. To do.

Next, as shown in step S23 of FIG. 4, primary heat treatment, that is, calcination is performed.
For example, as shown in FIG. 6, first, the temperature is raised from 0 ° C. to 100 ° C. in 0 minutes to ta1 minutes, for example, 7 minutes in an atmosphere of dry oxygen. Then, it replaces with the atmosphere of humidified oxygen, and raises temperature to 200 degreeC from ta1-ta2 in 35 minutes, for example. Thereafter, the temperature is increased from 250 to 1000 minutes from ta2 to ta3. Thereafter, the temperature is increased from ta3 to ta4, for example, to 300 ° C. in 100 minutes. Thereafter, the temperature is increased from ta4 to ta5, for example, to 400 ° C. in 20 minutes. Thereafter, the furnace is cooled instead of the dry oxygen atmosphere.
As a result, a calcined film is formed on the substrate 11 as shown in step S24 of FIG.

Next, as shown in step S25 of FIG. 4, secondary heat treatment, that is, main firing is performed.
For example, as shown in FIG. 7, the firing is first performed in a dry oxygen atmosphere from 0 minutes to tb1 minutes, and then is replaced by a mixed gas atmosphere of argon Ar and oxygen at 750 by tb1 to tb2. Increase the temperature to ° C. Thereafter, the temperature is raised to any one of 750 ° C. to 825 ° C. by tb2 to tb3. Thereafter, the temperature is maintained at any temperature between 750 ° C. and 825 ° C. from tb3 to tb4. Thereafter, the temperature is maintained from tb4 to tb5 in place of the dried atmosphere of mixed gas of argon and oxygen. Then, it cools to any temperature of 375 degreeC-525 degreeC from tb5 to tb6. Then, it replaces with dry oxygen atmosphere and it cools to the temperature of 325 degreeC-450 degreeC from tb6 to tb7. Thereafter, the temperature is maintained at 375 ° C. to 525 ° C. from tb7 to tb8. Thereafter, the furnace is cooled.

Thereby, as shown in step S26 of FIG. 4 and FIG. 1, the oxide superconductor 1 is manufactured. In the case of such a manufacturing method, the oriented superconducting layer 15 has a fluorine residue of 2.0 × 10 ^{16 to} 5.0 × 10 ¹⁹ atoms / cc and 1.0 × 10 ^{18 to} 5.0 × 10 ^20. Contains atoms / cc of residual carbon.

Next, the effect of this embodiment will be described.
The oxide superconductor 1 according to this embodiment includes an oriented superconducting layer having high orientation. An oriented superconducting layer can be formed on the metal tape. Furthermore, the area of the portion in contact with the orientation origin 13 on the lower surface of the oriented superconducting layer can be 0.3, preferably 0.1 or less, of the area immediately below the oriented superconducting layer. Thereby, an oriented superconducting layer can be formed directly on a solid having no lattice matching, for example, a metal. By setting it as such a structure, when a superconducting layer quenches, a quench current can be sent through a base metal.
In the manufacturing method of the oxide superconductor 1 of this embodiment, the oxide superconductor 1 can be manufactured in the atmosphere of a normal pressure. Thereby, production cost can be reduced.

The diffusion prevention layer 12 is an oxide layer made of a predetermined material, but is not limited to this. For example, a metal layer containing platinum (Pt) or a fluoride containing calcium fluoride (CaF ₂ ) may be used.
Moreover, although the orientation origin 13 is orientated on the diffusion prevention layer 12 using the orientation origin sheet | seat 16, it does not restrict to this. For example, the orientation origin 13 may be disposed directly on the diffusion prevention layer 12.

Further, although the oriented superconducting layer 15 includes DyBa ₂ Cu ₃ O _7-X , it is not limited to this.
For _example, it may be as including _{LnBa 2 Cu 3 O 7-X} . Here, Ln is a lanthanoid group excluding yttrium (Y), cerium (Ce), praseodymium (Pr), promethium (Pm), and lutetium (Lu). When the oriented superconducting layer 15 including the above material is manufactured, for example, Y (OCOCH ₃ ) ₃ , Gd (OCOCH ₃ ) ₃ , Tm (OCOCH ₃ ) ₃ and Er (OCOCH ₃ ) _{3 are used} as metal acetates. At least one material selected from the group consisting of:

(Second Embodiment)
Next, a second embodiment will be described.
FIG. 8 is a cross-sectional view illustrating an oxide superconductor according to the second embodiment.
As shown in FIG. 8, the oxide superconductor according to this embodiment is provided with a base material 21, a metal layer 22, and an oriented superconducting layer 15.

The base material 21 is, for example, a substrate containing a single crystal of lanthanum aluminate (LaAlO ₃ ). The upper surface of the base material 21 includes, for example, a (100) surface. The upper surface of the base material 21 includes an oriented portion. The crystal axis of the oriented portion on the upper surface of the substrate 21 includes, for example, an a-axis 21a and a b-axis 21b. The a-axis 21a and the b-axis 21b are, for example, two orthogonal directions in a plane parallel to the upper surface of the base material 21. The c-axis 21 c is a direction orthogonal to the upper surface of the base material 21. The degree of orientation is such that Δφ is within 10 degrees, preferably within 2 degrees. In the case of a single crystal substrate, Δφ is 0.5 degrees or less.
The metal layer 22 is selectively disposed on the base material 21. Therefore, the upper surface of the base material 21 includes a portion covered with the metal layer 22 and a portion not covered with the metal layer 22. The metal layer 22 includes, for example, a noble metal such as platinum (Pt).

  The oriented superconducting layer 15 is disposed on the substrate 21 and the metal layer 22. The base material 21 and the metal layer 22 are provided in contact with the lower surface of the oriented superconducting layer 15. The oriented superconducting layer 15 includes a single crystal portion. The single crystal portion includes crystal axes of an a-axis 15a, a b-axis 15b, and a c-axis 15c. In the single crystal portion, the crystal axes are oriented. In the direction in which the crystal axis of the single crystal portion in the oriented superconducting layer 15 is oriented, Δφ is within 10 degrees, preferably within 2 degrees.

  The a-axis 15a and the b-axis 15b are, for example, two orthogonal directions in a plane parallel to the upper surface of the substrate 21. For example, the a-axis 15 a is oriented with the a-axis 21 a of the base material 21, and the b-axis 15 b is oriented with the b-axis 21 b of the base material 21. Since the lengths of the a-axis and b-axis are almost the same, the structure is changed depending on the place. The c-axis 15 c is the c-axis 21 c direction of the base material 21. 90% or more of the oriented superconducting layer 15 contains oriented crystals. The crystal axis of the base material 21 functions as an origin of orientation for orienting the oriented superconducting layer 15 formed on the base material 21. On the other hand, the role that functions as the orientation origin in the metal layer 22 is almost zero compared to the crystal axis of the base material 21.

The oriented superconducting layer 15 includes, for example, a DyBa ₂ Cu ₃ O _7-X superconducting material.
The oriented superconducting layer 15 contains 2.0 × 10 ^{16 to} 5.0 × 10 ¹⁹ atoms / cc of fluorine residue and 1.0 × 10 ^{18 to} 5.0 × 10 ²⁰ atoms / cc of residual carbon.
Area SS immediately below the portion oriented at a swing angle of 10 degrees or less in oriented superconducting layer 15 and area SO in contact with substrate 21 oriented at a swing angle of 10 degrees or less on the bottom surface of oriented superconducting layer 15 The area SO <0.3 × the area SS, that is, the area SO is 0.3 or less of the area SS. Preferably, the area SO is 0.1 or less of the area SS. The thickness of the portion other than the region directly above the portion in contact with the substrate 21 in the oriented superconducting layer 15 is 1 micrometer (μm) or more. On the metal layer 22, the width of the oriented superconducting layer 15 in the direction parallel to the upper surface of the metal layer 22 is 1 micrometer (μm) or more, preferably 5 micrometers (μm) or more.

Next, a method for manufacturing the oxide superconductor 2 according to this embodiment will be described.
FIG. 9 is a process cross-sectional view illustrating a method for manufacturing an oxide superconductor according to the second embodiment.
First, as shown in FIG. 9, first, a base material 21 is prepared. The base material 21 is, for example, a substrate containing a single crystal of lanthanum aluminate (LaAlO ₃ ). The upper surface of the base material 21 includes, for example, a (100) surface. The upper surface of the base material 21 includes an oriented portion. Δφ of the oriented portion on the upper surface of the substrate 21 is within 10 degrees, preferably within 2 degrees.

  Next, a metal, for example, platinum (Pt) is deposited on the base material 21 by, for example, a sputtering method, and the metal layer 22 is formed on the base material 21. For example, the metal layer 22 is patterned by photolithography to partially cover the substrate 21 with the metal layer 22. The base material 21 and the metal layer 22 are referred to as a base. The foundation includes the oriented portion of the base material 21 and the metal layer 22.

Next, the coating solution is formed by performing the flow shown in FIG.
Next, a coating solution is applied onto the substrate 21. Then, a gel film is formed on the substrate 21 by spin coating. In the spin coating method, the acceleration time is 0.4 seconds and the rotation speed is 4000 r.s. p. m, holding time is 150 seconds.

Next, primary heat treatment, that is, calcination is performed.
The calcination is performed, for example, by a heat treatment step shown in FIG. Here, the time from ta2 to ta3 in FIG. 6 is 11 hours 43 minutes, and heat treatment is performed in a humidified pure oxygen atmosphere of 4.2%.
Thereby, a calcined film is formed on the substrate 11.

Next, secondary heat treatment, that is, main firing is performed.
For example, the main baking is performed by a heat treatment step shown in FIG. Here, tb3 to tb4 in FIG. 7 is maintained at a temperature of 800 ° C. in an atmosphere of 4.2% humidified 1000 ppm oxygen mixed argon, and the temperature is decreased to 525 ° C. from tb5 to tb6. Thereafter, the temperature is lowered to 450 ° C. from tb6 to tb7 in place of the dry oxygen atmosphere. Thereafter, the temperature is maintained at 450 ° C. from tb7 to tb8.

In this way, the oxide superconductor 2 is manufactured as shown in FIG. In the case of such a manufacturing method, the oriented superconducting layer 15 has a fluorine residue of 2.0 × 10 ^{16 to} 5.0 × 10 ¹⁹ atoms / cc and 1.0 × 10 ^{18 to} 5.0 × 10 ^20. Contains atoms / cc of residual carbon.

Next, effects of the second embodiment will be described.
In this embodiment, since the substrate 21 includes a single crystal, the orientation of the oxide superconductor can be improved.
Although it is generally difficult to form highly oriented oxides or crystals on the metal layer, according to the present embodiment, the top surface of the substrate 21 is the origin of orientation and the oxide is formed on the metal layer. The superconductor can be enlarged. Thereby, a highly oriented crystal can be formed on the metal layer. Configurations and effects other than those described above in the present embodiment are the same as those in the first embodiment described above.

Next, examples will be described.
Example 1
Metal acetates such as Dy (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) ₂ and Cu (OCOCH ₃ ) ₂ hydrate powders are dissolved in ion-exchanged water, respectively, and each reaction equimolar amount of trihydrate is added. A mixed solution was obtained by mixing and stirring with fluoroacetic acid (CF ₃ COOH) and mixing at a metal ion molar ratio of 1: 2: 3. The obtained mixed solution is put in an eggplant type flask, and subjected to reaction and purification in a rotary evaporator under reduced pressure for 12 hours to obtain a translucent blue gel or sol. A part of this gel or sol was dissolved in methanol to obtain a coating solution X of 1.52 M in terms of metal ions. This is a coating solution that has not been highly purified.

The obtained gel or sol was completely dissolved by adding methanol corresponding to about 100 times its weight, and the solution was reacted and purified again in a rotary evaporator under reduced pressure for 12 hours. Or a sol is obtained.
The obtained gel or sol was dissolved in methanol and diluted by using a volumetric flask to obtain 1.52 M coating solution A in terms of metal ions.

A substrate in which Pt was completely deposited on the top of a 10 mm square LaAlO ₃ (100) single crystal substrate by sputtering was prepared as a substrate 1S1, and a substrate covered by Pt only half was prepared as a substrate 1S2. Using the coating solution A, the spin time was applied to each substrate by an acceleration time of 0.4 seconds and a rotation speed of 4000 r. p. m. The film was formed under the condition that the holding time was 150 seconds, the heat treatment time between 200 ° C. and 250 ° C. was 11 hours 43 minutes under the conditions shown in FIG. 6, and the heat treatment was performed in a 4.2% humidified pure oxygen atmosphere. The calcined film 1Fm1c and the calcined film 1Fm2c were obtained from the substrate 1S1 and the substrate 1S2, respectively. Similarly, from the solution X which is not highly purified, a film was formed on the 1S2 substrate to obtain a calcined film 1Fm3c.

Subsequently, firing is performed at 800 ° C. in a 4.2% humidified 1000 ppm oxygen mixed argon atmosphere under the conditions shown in FIG. 7, dry pure oxygen is introduced at 525 ° C. or lower, and pure oxygen annealing is performed by holding at 450 ° C. It was obtained _{DyBa 2 Cu 3 O 7-x} . The sample names are Sample 1Fm1f, Sample 1Fm2f, and Sample 1Fm3f, respectively.

Samples 1Fm1f, 1Fm2f, and 1Fm3f were phase-identified by thin film X-ray diffraction, respectively. As a result, a good DyBa ₂ Cu ₃ O _7-x (00n) peak was observed. Compared with sample 1Fm2f, the peak of sample 1Fm1f was quite weak, but it was still a peak sufficient for measurement using the (103) plane, so the polar figure of sample 1Fm1f was measured. . Sample 1Fm2f is known to have an XRD spot of about 6 mm in diameter at the time of polar figure measurement. Whether or not the Pt film-forming surface of sample 1Fm2f which is only 10 mm in diameter is being measured is measured. It is unknown whether DyBa ₂ Cu ₃ O _7-x on the surface is being measured.

FIG. 10A is a polar diagram measured by a thin film X-ray diffraction method in the oriented superconducting layer, FIG. 10B is a schematic plan view illustrating the crystal structure of the oriented superconducting layer, and FIG. It is a schematic cross section which illustrates the crystal structure of an oriented superconducting layer.
As shown in FIG. 10 (a), a peak appears at a position of 44 to 46 degrees from the apex, but the peak intensity is almost donut-shaped and the c-axis is oriented vertically, but the in-plane orientation varies. It can be seen that the structure is uniaxially oriented.
The LnBa ₂ Cu ₃ O _7-x superconductor (Ln is Y or a lanthanoid group element) is not limited to DyBa ₂ Cu ₃ O _7-x , and crystal growth in the c-axis direction is slow, and crystals in the a-axis and b-axis directions The growth is said to be fast. The ratio is said to be about 1: 100 to 1: 1000. As shown in FIG. 10 (a), in the oriented superconducting layer, only the c-axis orientation is aligned, but the in-plane orientation directions are scattered.

As shown in FIGS. 10B and 10C, when viewed from above, the c-axis oriented structure is aligned on the substrate, but the in-plane orientation is inconsistent.
This result suggests that the TFA-MOD method using a high-purity solution tends to form a c-axis oriented structure when it is not affected by the orientation and the like from the substrate. In the TFA-MOD method, since particles grow in a liquid phase, the particles are likely to be bonded in the in-plane direction where the growth rate is fast, and the c-axis is physically easily oriented in the direction perpendicular to the substrate. FIG. 10 (a) shows that the alignment layer is completed by applying another uniaxial alignment force based on the experimental fact that was found to be c-axis alignment and probably the first in the world. This phenomenon has not been confirmed when a high-purity solution is not used. As the cause, it is assumed that impurities in the solution remain on the film surface and inhibit lateral crystal growth.

Note that Pt and LnBa ₂ Cu ₃ O _7-x superconductor are close in lattice constant and lattice matched. For example, Pt is a rectangular parallelepiped with an axial length of 3.92 mm in the JCPDS card 00-004-0802. According to JCPDS card 00-040-0211, the DyBa ₂ Cu ₃ O _7-x superconductor has a-axis length and b-axis length of 3.89 mm and 3.82 mm, respectively, and a small lattice matching of Pt and less than 1% Will have. This Pt layer is formed on a LaAlO ₃ (100) substrate. According to JCPDS card 01-085-0848, it has an axial length of 3.79 mm of LaAlO ₃ and has a good lattice matching with Pt of 3% or less. Nevertheless, as shown in FIG. 10 (a), the reason for not being oriented is that the polarity is related.

Since LaAlO ₃ and DyBa ₂ Cu ₃ O _7-x are metal oxides, the metal is positively charged and oxygen is negatively charged and has a large polarity. This is due to the difference in electronegativity, and substances having large polarities tend to be oriented by taking over the lattice matching in a film having a constant energy of about 600 ° C. or higher. On the other hand, since Pt is a metal, all Pt atoms located on the surface do not exist more than a large piece of charge. That is, there is almost no polarity. Therefore, when DyBa ₂ Cu ₃ O _7-x is formed directly on LaAlO ₃ , a clean orientation structure is formed, but it seems that the orientation is basically not inherited through the Pt layer. .

FIG. 11 is a schematic cross-sectional view when an oriented superconducting layer is formed on a base material and a metal layer formed on the base material.
As shown in FIG. 11, sample 1Fm2f is obtained by depositing only half of Pt and performing superconducting deposition on the top. This sample 1Fm2f is for the purpose of measuring the propagation distance of the alignment layer, and is an examination of how much the alignment layer propagation distance is from the Pt film formation boundary layer. Since evaluation cannot be performed with XRD, evaluation was performed using a high-resolution TEM and a diffraction image. Cross sections were observed at positions where the distance moved from the boundary surface to the Pt side was 5 μm, 10 μm, 20 μm, and 40 μm, respectively. Many observations were made because it was thought that if there was an influence of the propagation of the alignment layer from a place where it was not visible (for example, the back side), it would appear. This is because it is considered that the propagation of the alignment layer can be confirmed if there is a certain tendency at the four positions.

FIG. 12 is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position of 5 μm from the Pt film formation interface.
It is proved from the result of FIG. 10A that a structure that does not lattice match is formed in the film formation on the Pt layer. That is, although the c-axis is formed upward in the figure even when the DyBa ₂ Cu ₃ O _7-x superconducting layer is formed, the direction should be random in the in-plane direction. As shown in FIG. 12, when the LaAlO ₃ substrate is used as a reference, the orientations of the DyBa ₂ Cu ₃ O _7-x superconducting layer and the LaAlO ₃ single crystal substrate coincide with each other. That is, this result shows that the alignment layer propagates almost completely at the position of 5 μm from the LaAlO ₃ portion as the origin of alignment.

  Also, as shown in FIG. 12, the distance between the metal layer and the oxide alignment layer is 5 nm or less, and an alignment layer that is more closely attached to the metal than the alignment layer formed by the magnetic field can be realized. Further, as can be seen from this figure, a clear atomic image can be observed at positions up to 5 μm. This indicates Δφ <0.2 degrees, and the state is considered to spread equally on both sides of the orientation origin.

FIG. 13 is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position 10 μm from the Pt film formation interface.
As shown in FIG. 13, in this cross-sectional TEM image, a clear lattice image is not seen, and the diffraction image shown in the upper right shows a result that the orientation is propagated though it is weak. A strong orientation layer propagating tendency was observed at the position of 5 μm, but it was found that the c-axis orientation was weakened to the extent that it could be confirmed by a diffraction image at the position of 10 μm.

FIG. 14 is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position 20 μm from the Pt film formation interface.
As shown in FIG. 14, in this cross-sectional TEM image, not only the arrangement of atoms is not observed, but also the diffraction image is further disturbed and the orientation does not propagate.
FIG. 15 is a high-resolution cross-sectional TEM photograph of the oriented superconducting layer at a position 40 μm from the Pt film formation interface.
As shown in FIG. 15, the alignment layer hardly propagates, and it is only observed that a structure close to c-axis uniaxial alignment is formed on Pt.

From the above results, the propagation of the alignment layer under these conditions is oriented at an atomic level of Δφ <0.2 degrees up to 5 μm, and the effect is confirmed at 10 μm although the biaxial orientation is weak, and further weak at 20 μm. Thus, 40 μm was in a state where there was almost no influence. It is thought that this alignment layer propagation distance can be increased by lowering the heat treatment temperature or reducing the amount of humidification, and has not been subjected to direct high-resolution TEM observation. The result supports it. Although not observed at all different phase, such as the respective TEM observations CuO and the inside of the membrane from Y ₂ O _3, which is due to film formation by a high-purity solution. As shown by the result of Sample 1Fm3f described later, it is considered that a high-purity solution is necessary for propagation of the alignment layer.

Even if this condition is used, the results show that the alignment layer propagates when the linear alignment origin is set at an interval of 10 μm or less. From the past results, the TFA-MOD method has formed a good superconducting layer even when Δφ of the base metal or CeO ₂ intermediate layer is 8 degrees. This is because the superconducting layers flow superconducting currents through the low-angle grain boundaries, although the characteristics are somewhat reduced at the low-angle grain boundaries. However, the smaller the low-angle grain boundary, the larger the loss of superconducting current. From experiments using bicrystals, it is believed that if the low-angle grain boundary is 4 degrees or less, the attenuation of the superconducting current is small.

  This is the origin of orientation that is limited in principle by the IBAD (Ion Beam Assisted Deposition) method and the RABiTS (Rolling Assisted Biaxially Textured Substrate) method. This corresponds to Δφ when arranged on the substrate. This is because ceramic nanofibers, which are orientation sources, are dispersed in a solution using a dispersing material, and are included in the organic matter that is burned by heating to reduce the fiber's Δφ to 2 degrees or less (almost zero). When pasted on the substrate, the fibers of orientation origin are arranged with a small Δφ. If only the orientation origin, which is an oxide, remains after firing, a highly oriented orientation origin can be realized by a simple method. The oxide superconductor and the manufacturing method thereof according to the first and second embodiments are one of the technologies for realizing an oriented structure having a small degree of orientation that cannot be realized in principle by the IBAD method or the RABiTS method. is there.

High resolution TEM observation of sample 1Fm3f was performed in the same manner. In this sample, no alignment layer was observed even at a position of 5 μm from the Pt interface. Since there is a considerable distance from the Pt interface to the observation position, it is difficult to know what phenomenon is occurring by high-resolution TEM observation of high-magnification observation, but the c-axis oriented structure is formed from the results of XRD measurement. It seems that only the propagation of the alignment layer did not go well from the orientation origin. Probably, a different phase (CuO, Y ₂ O _3, etc.) that is not a superconducting layer derived from impurities in the solution was formed, and the alignment layer did not propagate. It is considered that the orientation layer propagation phenomenon requires a high-purity solution of the TFA-MOD method and a heat treatment condition with characteristics.

(Example 2)
Metal acetates such as Y (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) ₂ and Cu (OCOCH ₃ ) ₂ hydrate powders are dissolved in ion-exchanged water, respectively, and reaction equimolar amounts of CF are obtained. ₃ COOH was mixed and stirred, and mixed at a metal ion molar ratio of 1: 2: 3 to obtain a mixed solution. The obtained mixed solution is put in an eggplant type flask, and subjected to reaction and purification in a rotary evaporator under reduced pressure for 12 hours to obtain a translucent blue gel or sol.

The obtained gel or sol was completely dissolved by adding methanol corresponding to about 100 times its weight, and the solution was reacted and purified again in a rotary evaporator under reduced pressure for 12 hours. Or a sol is obtained.
The obtained gel or sol was dissolved in methanol and diluted by using a volumetric flask to obtain 1.52 M coating solution B in terms of metal ions. The flowchart up to the production of the superconductor is as shown in FIG.

Further, instead of Y (OCOCH ₃ ) ₃ described above, Gd (OCOCH ₃ ) ₃ , Tm (OCOCH ₃ ) ₃ and Er (OCOCH ₃ ) ₃ are used, and the coating solution C and solution D of 1.52 M in terms of metal ions are used. Solution E was obtained.

Four substrates 2S1 that were completely covered with Pt on the top of a 10 mm square LaAlO ₃ (100) single crystal substrate and four substrates 2S2 that were left half covered with Pt were prepared. Using the coating solutions B, C, D, and E, a film is formed on each substrate by the spin coat method under the same conditions as in the first embodiment, and under the same conditions as in the first embodiment shown in FIG. A heat treatment is performed, and the calcined film 2Fm1Bc, the calcined film 2Fm1Cc, the calcined film 2Fm1Dc, and the calcined film 2Fm1Ec are formed on the substrate 2S1, and the calcined film 2Fm2Bc, the calcined film 2Fm2Cc, the calcined film 2Fm2Dc, and the calcined film are calcined on the substrate 2S2. A membrane 2Fm2Ec was obtained.

Subsequently, heat treatment is performed under the same conditions as in Example 1 described above shown in FIG. _7, to obtain a _{LnBa 2 Cu 3 O 7-x} . The sample names are sample 2Fm1Bf, sample 2Fm1Cf, sample 2Fm1Df, sample 2Fm1Ef on the substrate 2S1, and sample 2Fm2Bf, sample 2Fm2Cf, sample 2Fm2Df, and sample 2Fm2Ef on the substrate 2S2, respectively.

As a result of phase identification of all the films by thin film X-ray diffraction, a good LnBa ₂ Cu ₃ O _7-x (00n) peak was observed. Although the LnBa ₂ Cu ₃ O _7-x (00n) peak of sample 2Fm1Bf, sample 2Fm1Cf, sample 2Fm1Df, and sample 2Fm1Ef was weak in relative comparison, it was still sufficient for measurement in a polar figure using the (103) plane It was found that a uniaxially oriented structure (oriented only in the c-axis) was obtained by polar pattern measurement as in Example 1.

  Sample 2Fm2Bf, Sample 2Fm2Cf, Sample 2Fm2Df, and Sample 2Fm2Ef are formed by depositing only half of Pt and performing superconducting film formation thereon. These samples were intended to measure the propagation distance of the alignment layer, and were evaluated by high-resolution TEM and diffraction images as in Example 1. Cross sections were observed at distances of 5 μm and 10 μm respectively moved from the boundary surface to the Pt side. As a result of observation, a good biaxially oriented structure was observed at a distance of 5 μm. Even if the element type of Ln was changed, it was not observed in this experiment in special cases.

Example 3
The peripheral part was scraped off to form a LaAlO ₃ protrusion having a width of 5 μm and a length of 100 μm on the top of a 10 mm square LaAlO ₃ (100) single crystal substrate, and Pt film formation was performed including that part. Further, the portion was polished and washed, and a substrate 3S1 having a structure in which a LaAlO ₃ single crystal substrate having a width of 5 μm was sandwiched between Pt portions was prepared. In the above substrate preparation, a substrate 3S2 having a width of 1 μm was also prepared at the same time.

  Using the coating solution A, a film is formed on each substrate under the same conditions as in the first embodiment, and the same heat treatment as in the first embodiment shown in FIG. 6 is performed, and the calcined film 3Fm1c and the calcined film are respectively formed. 3Fm2c was obtained.

Subsequently, the same heat treatment as in Example 1 described above shown in FIG. _7, to obtain a _{DyBa 2 Cu 3 O 7-x} . The sample names are Sample 3Fm1f and Sample 3Fm2f, respectively.

As a result of phase identification of all the films by the thin film X-ray diffraction method, a good DyBa ₂ Cu ₃ O _7-x (00n) peak was observed. This DyBa ₂ Cu ₃ O _7-x (00n) peak appears to contain a uniaxially oriented portion and a biaxially oriented portion, but the X-ray irradiation region in XRD measurement has a diameter of about 6 mm, so separation is not possible. Is possible. Each cross-section TEM observation was performed.

In sample 3Fm1f, a good biaxially oriented superconducting structure was observed not only immediately above the 5 μm width of the LaAlO ₃ substrate portion but also at 5 μm positions on both sides thereof. That is, the LaAlO ₃ portion that is the origin of orientation has a width of 5 μm, but at least the superconducting layer portion has a structure in which the orientation layer is continuous up to a position of 15 μm in width. If the region where the swing angle is within 10 degrees with respect to the lattice matching direction in the orientation origin layer is defined as region So, it is 5 μm × length 100 μm, and the c-axis alignment region within the swing angle of 10 degrees in the superconducting layer is defined as region Ss. 15 μm × length 100 μm. Conventionally, the region Ss which is an alignment source has almost the same area as the region So, and as far as it can be known, there is no report of a structure satisfying the region So / region Ss <0.95. The structure obtained this time is a region So / region Ss = 0.33, which is the first structure realized by contacting a biaxially oriented superconducting layer and a metal Pt layer.

In sample 3Fm2f, a good biaxially oriented superconducting structure was observed not only immediately above the 1 μm width of the LaAlO ₃ substrate portion but also at 5 μm positions on both sides thereof. That is, the LaAlO ₃ portion, which is the origin of orientation, has a width of 1 μm, but at least the superconducting layer portion has a structure in which the orientation layer is continuous up to a position of 11 μm in width. The region So is 1 μm × 100 μm in length, and similarly, the region Ss is 11 μm × 100 μm in length. The region So / region Ss = 0.091 is small, and the biaxially oriented superconducting layer is in contact with the metal Pt layer.

  Conventionally, the structure of region So / region Ss <0.95 could not be realized, but in this example, a structure in which region So / region Ss is less than 0.30 or a structure less than 0.10 was realized. The structure in which the alignment layer is formed directly on the metal has also been realized for the first time.

Example 4
Pt was deposited on the entire surface of a 10 mm square LaAlO ₃ (100) single crystal substrate. A strip of width 1 μm × thickness 100 nm × length 100 μm is cut out from another LaAlO ₃ (100) single crystal substrate, and only one substrate is placed on Pt, the substrate 4S1, and the three strips are oriented twice with respect to the orientation direction. The substrate placed so as to be within the range is referred to as a substrate 4S2. Three strips were arranged on the Pt of the substrate 4S2 almost in parallel (within a deviation angle of 2 degrees or less) with an interval of 10 μm.

  Using the coating solution A, a film is formed on each substrate by the spin coating method under the same conditions as in the first embodiment, and the same heat treatment as in the first embodiment shown in FIG. Those obtained by forming a calcined film on the substrate 4S2 are referred to as a calcined film 4Fm1c and a calcined film 4Fm2c.

Subsequently, the same heat treatment as in Example 1 shown in FIG. 7 was performed to obtain DyBa ₂ Cu ₃ O _7-x . The sample names are Sample 4Fm1f and Sample 4Fm2f, respectively.

As a result of phase identification of all the films by the thin film X-ray diffraction method, a good DyBa ₂ Cu ₃ O _7-x (00n) peak was observed. This DyBa ₂ Cu ₃ O _7-x (00n) peak appears to contain a uniaxially oriented portion and a biaxially oriented portion, but the X-ray irradiation region in XRD measurement has a diameter of about 6 mm, so separation is not possible. Is possible. In order to examine the internal structure, cross-sectional TEM observation was performed.

In sample 4Fm1f, a good biaxially oriented superconducting structure was observed not only immediately above the 1 μm width of the LaAlO ₃ substrate portion but also at 5 μm positions on both sides thereof. That is, the LaAlO ₃ portion, which is the origin of orientation, has a width of 1 μm, but at least the superconducting layer portion has a structure in which the orientation layer is continuous up to a position of 11 μm in width. If the region where the swing angle is within 10 degrees with respect to the lattice matching direction in the orientation origin layer is defined as region So, it is 1 μm × length 100 μm, and the c-axis alignment region within the swing angle of 10 degrees in the superconducting layer is defined as region Ss. 11 μm × length 100 μm. The structure obtained this time is region So / region Ss = 0.091.

In the sample 4Fm2f, a good biaxially oriented superconducting structure was observed at a continuous 33 μm position including 5 μm on both sides as well as the LaAlO ₃ substrate portion having a total width of 3 μm. That is, the LaAlO ₃ portion, which is the origin of orientation, has a width of 3 μm, but at least the superconducting layer portion has a structure in which the orientation layer is continuous up to a position of 33 μm in width. If the region where the swing angle is within 10 degrees with respect to the lattice matching direction in the orientation origin layer is defined as region So, it is 3 μm × 100 μm in length, and the c-axis alignment region within the swing angle of 10 degrees in the superconducting layer is defined as region Ss. 33 μm × length 100 μm. The structure obtained this time is region So / region Ss = 0.091.

The structure realized by the sample 4Fm2f is a structure in which Δφ of the superconducting layer formed from a plurality of orientation sources is less than twice on the metal. Since it is a small region, Δφ measurement of this part cannot be observed using polar figure measurement, but the alignment layer propagates from the LaAlO ₃ strip that is the origin of orientation, and it is good at a small tilt grain boundary. It seems that superconducting properties can be obtained. In the conventional IBAD method and RABiTS method, such a small Δφ structure cannot be formed on a metal tape in principle. This is the first oxide layer structure having a small Δφ obtained on the metal realized by this embodiment.

(Example 5)
Pt was deposited on the entire surface of a 10 mm square LaAlO ₃ (100) single crystal substrate. A strip of width 1 μm × thickness 100 nm × length 100 μm was cut out from another LaAlO ₃ (100) single crystal substrate, and only one substrate placed on Pt was 5S1, and the three strips were within 2 degrees with respect to the orientation direction. The substrate installed so as to be 5S2. Three strips were placed on Pt of 5S2 almost in parallel with an interval of 10 μm.

  Using the coating solution B, a film was formed on each substrate by the same spin coating method as in Example 1 described above, and the same heat treatment as in Example 1 shown in FIG. 6 was performed, and the substrates 5S1 and 5S2 were formed. The calcined film is formed as a calcined film 5Fm1c and a calcined film 5Fm2c.

Subsequently, the same heat treatment as in Example 1 shown in FIG. 7 was performed to obtain YBa ₂ Cu ₃ O _7-x . The sample names are Sample 5Fm1f and Sample 5Fm2f, respectively.

As a result of phase identification of all the films by the thin film X-ray diffraction method, a good YBa ₂ Cu ₃ O _7-x (00n) peak was observed. The YBa ₂ Cu ₃ O _7-x (00n) peak appears to contain a uniaxially oriented portion and a biaxially oriented portion. However, since the X-ray irradiated region in XRD measurement has a diameter of about 6 mm, separation is not possible. Is possible. In order to examine the internal structure, cross-sectional TEM observation was performed.

In sample 5Fm1f, a good biaxially oriented superconducting structure was observed not only immediately above the 1 μm width of the LaAlO ₃ substrate portion but also at 5 μm positions on both sides thereof. That is, the LaAlO ₃ portion, which is the origin of orientation, has a width of 1 μm, but at least the superconducting layer portion has a structure in which the orientation layer is continuous up to a position of 11 μm in width. If the region where the swing angle is within 10 degrees with respect to the lattice matching direction in the orientation origin layer is defined as region So, it is 1 μm × length 100 μm, and the c-axis alignment region within the swing angle of 10 degrees in the superconducting layer is defined as region Ss. 11 μm × length 100 μm. The structure obtained this time is region So / region Ss = 0.091.

In sample 5Fm2f, a good biaxially oriented superconducting structure was observed at a continuous 33 μm position including 5 μm on both sides as well as a total 3 μm width of the LaAlO ₃ substrate portion. That is, the LaAlO ₃ portion, which is the origin of orientation, has a width of 3 μm, but at least the superconducting layer portion has a structure in which the orientation layer is continuous up to a position having a width of 33 μm. If the region where the swing angle is within 10 degrees with respect to the lattice matching direction in the orientation origin layer is defined as region So, it is 3 μm × 100 μm in length, and the c-axis alignment region within the swing angle of 10 degrees in the superconducting layer is defined as region Ss. 33 μm × length 100 μm. The structure obtained this time is So / Ss = 0.091.

The structure realized by the sample 5Fm2f is a structure in which Δφ of a superconducting layer formed from a plurality of orientation sources is less than twice even though it is on a metal. Since it is a small region, Δφ measurement of this part cannot be observed using polar figure measurement, but the orientation layer propagates from the LaAlO ₃ strip that is the origin of orientation, and good superconductivity at a small tilt grain boundary It seems that characteristics can be obtained. In principle, the conventional IBAD method and RABiTS method cannot form such a small Δφ structure on a metal tape. It is a structure that can only be obtained by highly arranging the orientation origins.

(Example 6)
Pt was deposited on the entire surface of a 10 mm square LaAlO ₃ (100) single crystal substrate. A strip having a width of 1 μm, a thickness of 100 nm, and a length of 100 μm was cut out from a CeO ₂ (100) film formed on another substrate with a thickness of 150 nm, and the three strips were set to be within 2 degrees with respect to the orientation direction. The substrate is a substrate 6S1. On the Pt of the substrate 6S1, three strips are arranged substantially in parallel with an interval of 6 μm.

  Using the coating solution A, a film was formed on each substrate by the same spin coating method as in Example 1 described above, and the same heat treatment as in Example 1 shown in FIG. 6 was performed, and a calcined film was formed on the substrate 6S1. The formed film is referred to as a calcined film 6Fm1c.

Subsequently, the same heat treatment as in Example 1 shown in FIG. 7 was performed to obtain DyBa ₂ Cu ₃ O _7-x . The sample name is sample 6Fm1f.

As a result of phase identification of all the films by the thin film X-ray diffraction method, a good DyBa ₂ Cu ₃ O _7-x (00n) peak was observed. This DyBa ₂ Cu ₃ O _7-x (00n) peak appears to contain a uniaxially oriented portion and a biaxially oriented portion, but the X-ray irradiation region in XRD measurement has a diameter of about 6 mm, so separation is not possible. Is possible. In order to examine the internal structure, cross-sectional TEM observation was performed. This alignment film is considered to have a structure inclined in the in-plane direction of 45 degrees. This is because the lattice multiplier of CeO ₂ is about twice that of the superconductor (1.41 times), so that the one tilted 45 degrees in the horizontal plane matches as the lattice.

In the sample 6Fm1f, a good biaxially oriented superconducting structure was observed not only immediately above the CeO ₂ portion with a width of 3 μm, but also in a region between the three locations and at positions of 3 μm on both sides. That is, the CeO ₂ portion that is the origin of orientation has a width of 3 μm, but at least the superconducting layer portion has a structure in which the orientation layer is continuous up to a position of 21 μm in width. If the region where the swing angle is within 10 degrees with respect to the lattice matching direction in the orientation origin layer is defined as region So, it is 3 μm × 100 μm in length, and the c-axis alignment region within the swing angle of 10 degrees in the superconducting layer is defined as region Ss. 21 μm × length 100 μm. The structure obtained this time is region So / region Ss = 0.145.

  As described above, by using these examples, it is possible to form a highly oriented structure of Δφ <2 on a metal tape, which has been impossible in principle by the IBAD method or the RABiTS method. . In addition, the region So / region Ss, which is the ratio of the orientation origin to the orientation layer, has been almost 1 so far, but a structure below 0.3 or 0.1 can be realized. Forming the oxide alignment layer directly on the metal is a difficult technique from the viewpoint of polarity, but the structure can also be realized by propagating the alignment structure from the alignment layer separately provided in these examples. There is an advantage that when the superconducting layer is quenched, a quench current flows through the base metal. From the viewpoint of an oxide having this structure, it is probably the first structure realized in this example.

If this method is used to form a diffusion prevention layer by MOD and lay and fire a tape whose orientation origin is arranged in a sheet, it is not only a non-vacuum process together with the TFA-MOD method. , A structure having a small Δφ is completed, and a high-performance superconducting wire can be expected. The diffusion prevention layer may be not only an oxide but also a fluoride such as CaF ₂ . In addition, the orientation-origin fibers can be arranged as a sheet by forming a thin line including the fiber and extending it into a tape shape so that the orientation origin can be arranged with a small Δφ. If the sheet is bonded and then baked strongly to prevent burning other than the oxide, only the orientation origin having a small Δφ can be formed. As described above, this embodiment is a part of a technique for forming a small Δφ oxide structure in the form of a metal tape, which could not be achieved by the IBAD method and the RABiTS method.

(Comparative example)
Next, a comparative example will be described.
In oxide superconductors, the superconducting layer has an yttrium or lanthanoid perovskite structure, but its orientation originates not in the superconducting layer but in the underlying layer. Superconducting circuit formation technology that forms a film on a single crystal uses the orientation of the superconducting layer by utilizing the degree of orientation of the single crystal, but in wire and coil applications, a superconducting film is formed on a metal tape. An orientation origin is necessary.

  Regarding the alignment layer formation technology, the main ones are the alignment oxide layer formation technology by IBAD (Ion Beam Assisted Deposition) method and the rolling technology such as RABiTS (Rolling Assisted Biaxially Textured Substrate) method. There are two types of techniques for orienting the oxide layer on top. In addition to this, formation of an alignment layer by liquid phase formation and magnetic field force has also been proposed, but results comparable to the alignment layer formation technology by the IBAD method or RABiTS method have not been obtained. The main alignment layer formation is the IBAD method and the RABiTS method described above. The two alignment layer forming techniques will be described below.

  The IBAD method is a technique in which an oxide is deposited on an unoriented metal while irradiating argon ions, and the degree of orientation is gradually improved. In many cases, Hastelloy-C is used for the non-oriented metal, and argon ions are used for the ion source. The metal oxide to be oriented is YSZ in the early days of the appearance of the IBAD method, and then becomes Ga2Zr2O7, and in recent years, there is much MgO. This technique is a technique for forming an oxide alignment layer at about room temperature and about 70 ° C. This is a technique in which the degree of orientation of the deposited oxide layer is gradually improved by scattering oxide particles in a vacuum and irradiating with an argon ion beam. The orientation principle is not completely elucidated.

  The biggest problem with this technique is that the improvement in the degree of orientation is moderate and it is considered that there is a limit value in the degree of orientation. When the deposited layer is formed on the non-oriented base metal tape (Hastelloy-C) by the IBAD method, Δφ of the initial film-forming layer having a film thickness of about 10 nm is as large as about 20 degrees. In addition, the improvement of Δφ is very moderate because the substrate temperature at the time of film formation is as low as about 70 ° C., and Δφ may be about 10 degrees even when the film formation layer by IBAD method is about 1 μm.

  In order to remedy this drawback of the IBAD method, technical development has been carried out to improve Δφ in a deposited layer having a relatively thin alignment layer. That is a method of forming a non-oriented layer directly under the IBAD layer. Since the improvement of the alignment layer by the IBAD method does not occur without the assistance of an ion beam, at least irradiation of this ion is involved in improving the degree of alignment.

When the flying oxide particles assisted by the ion beam land on the substrate, and there is an orderly large polarity on the substrate, the orientation improvement by the IBAD method in which low-temperature film formation is performed is It is gentler than when the layer is made amorphous. In the case of an amorphous material having a small polarity, it is considered that oxide particles assisted by argon ions can move more freely, but details are unknown.
This amorphous layer is not a single layer, it seems that the orientation is easier to improve in the case of two layers. At present, a commercial superconducting wire has an orientation origin layer by the IBAD method on top of two underlying amorphous layers. Two alignment oxide layers are formed. The superconducting layer is formed on the upper part through a laminated structure of as many as five layers.

  It is necessary to consider how much the degree of orientation is improved in principle by this IBAD method. Although the principle of the IBAD method has not been completely elucidated, there is no doubt that the argon ions have some sort of assistance to the deposited oxide to improve the orientation. If the argon ions are not unidirectionally irradiated, the alignment layer is probably arranged randomly. Therefore, it seems that at least the degree of parallelism with which the argon ions are irradiated is involved in improving the orientation.

  It is known that the best orientation can be obtained by irradiating the argon ions at an angle of 55 degrees when orienting the YSZ layer. The parallelism of argon ions and the Δφ of the oxide layer that forms the alignment layer affected by the parallelism are not 1: 1, and at least the argon ions can only affect the deposited oxide instantaneously when flying. Therefore, it is expected that the degree of orientation is improved only when the parallelism of argon ions is 1/2 or 1/3. Although it is the parallelism of the argon ions, the particles that repel electrically because they are irradiated as ions fly with a spread. Further, the ion irradiation source cannot make the distance to the film formation sample infinitely large, and the irradiation source itself has a size, and since argon ions come from there, parallel ion irradiation does not occur. It is considered that Δφ forms an angle of about 5 degrees. It is considered that an alignment layer having a large Δφ is formed, but here, there is a possibility that the factor can be made close to 1 times by optimization. From these discussions, Δφ obtained by infinitely increasing the film thickness by the IBAD method is expected to be 5 degrees or more.

  In superconducting wires whose superconducting properties are improved by improving Δφ, there are many reports that Δφ of the intermediate layer formed by the IBAD method is about 6 degrees. Of course, a small sample with a short Δφ may be obtained, but the minimum Δφ for alignment film obtained by the IBAD method is considered to be about 5 degrees.

  Next, the RABiTS method will be described. Here, a metal such as Ni-W is rolled and plastically deformed to orient the atoms in the rolling direction, and an oxide layer is formed on the top to propagate the orientation, and about two oxide layers are stacked. This is a technique for forming an orientation template of a superconductor. The plastic deformation of the metal cannot be repeated indefinitely, and the degree of orientation is improved only to the extent that the tape is not broken. The Δφ of the orientation texture reported at present is 6 to 8 degrees. This is Δφ of the rolled metal, but this Δφ is not deteriorated even in the upper three metal oxide layer stacks. Rather, it is considered that the upper metal oxide layer has self-orientation depending on conditions, but Δφ is often improved by about 0.2 to 0.3 degrees.

The first oxide layer directly on the metal formed by the RABiTS method has a narrow film formation condition because the alignment needs to be inherited from the metal alignment layer having no polarity to the oxide layer. If the condition is not met, the degree of orientation will be extremely deteriorated. The first layer is also called a SEED layer, and Y ₂ O ₃ or CeO ₂ is often used. The second layer is a layer that prevents diffusion from the base metal, is called a diffusion prevention layer (barrier layer), and YSZ or the like is often used. Since both the first layer and the second layer are polar, it is considered that film formation with the orientation degree maintained is easy. Similarly, the third layer is a layer which is also called a cap layer because it is necessary to prevent a chemical reaction such as HF in the reaction by the TFA-MOD method.

  These three alignment layers are all formed at around 700 ° C., and the formed oxide particles have sufficient energy, so that the degree of alignment tends to be slightly improved. This is a so-called self-orientation property. This self-orientation may show its properties because the superconducting layer itself is an oxide layer. Although it is this self-orientation property, it is known that even if the four layers including the superconducting layer are combined, the improvement is about 0.3 degree. That is, when Δφ of the rolled metal layer is 6 degrees, if the superconducting layer has good film formation conditions, Δφ = 5.6 degrees. However, it is difficult to realize an alignment layer with Δφ of 6 degrees or less by this RABiTS method.

  According to the embodiment described above, it is possible to provide an oxide superconductor, an alignment oxide thin film, and a method for manufacturing the oxide superconductor capable of improving the orientation.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

1, 2: oxide superconductor, 11: base material, 12: diffusion preventing layer, 13: orientation origin, 14 non-oriented layer, 15: oriented superconducting layer, 15a: a axis, 15b: b axis, 15c: c axis 16: Orientation origin sheet, 17: Binder, 21: Base material, 22: Metal layer, 23: Coating solution, 24: Gel film, S13, SO, SS: Area, Ss, So: Region, 1S1, 1S2, 3S1 3S2, 4S1, 4S2: Substrate, 1Fm1c, 1Fm2c, 1Fm3c, 2Fm1Bc, 2Fm1Cc, 2Fm1Dc, 2Fm1Ec, 2Fm2Bc, 2Fm2Cc, 2Fm2Dc, 2Fm2Ec, 3Fm1c, 3Fm2c, 4Fm1c, 4Fm2c, 5F1 1Fm2f, 1Fm3f, 2Fm1Bf, 2Fm1Cf, 2Fm1Df, Fm1Ef, 2Fm2Bf, 2Fm2Cf, 2Fm2Df, 2Fm2Ef, 3Fm1c, 3Fm2c, 4Fm1f, 4Fm2f, 5Fm1f, 5Fm2f: sample

The oriented superconducting layer 15 contains 2.0 × 10 ^{16 to} 5.0 × 10 ¹⁹ atoms / cc of fluorine and 1.0 × 10 ^{18 to} 5.0 × 10 ²⁰ atoms / cc of carbon. This is a residue derived from the TFA-MOD method and inevitably left by a liquid-phase calcination reaction at chemical equilibrium.
The total area SO of the area SS immediately below the portion within Δφ10 degrees in the oriented superconducting layer 15 and the area S13 of the portion in contact with the orientation origin 13 oriented at the swing angle within 10 degrees on the lower surface of the oriented superconducting layer 15. The area SO <0.3 × the area SS, that is, the area SO is less than 0.3 times the area SS. Preferably, the area SO is not more than 0.1 times the area SS. In the present specification, for example, the area SS and the area SO, may represent a region _{S S} and the area _{S O.} The short side of the portion other than the region directly above the portion in contact with the alignment origin 13 in the alignment superconducting layer 15 may be about 10 nanometers or 1 micrometer or more. Since several unit cells are sufficient to function as the orientation origin, the width of the oriented superconducting layer 15 in the direction parallel to the upper surface of the non-oriented layer 14 is just above the portion in contact with the non-oriented layer 14. , 30 nanometers (nm) or more, preferably 5 micrometers (μm) or more. The oxide superconductor 1 containing oriented oxide is also a thin film of oriented oxide.

Next, the effect of this embodiment will be described.
The oxide superconductor 1 according to this embodiment includes an oriented superconducting layer having high orientation. An oriented superconducting layer can be formed on the metal tape. Furthermore, the area of the portion in contact with the orientation origin 13 on the lower surface of the oriented superconducting layer can be less than 0.3 times , preferably less than 0.1 times the area immediately below the oriented superconducting layer. Thereby, an oriented superconducting layer can be formed directly on a solid having no lattice matching, for example, a metal. By setting it as such a structure, when a superconducting layer quenches, a quench current can be sent through a base metal.
In the manufacturing method of the oxide superconductor 1 of this embodiment, the oxide superconductor 1 can be manufactured in the atmosphere of a normal pressure. Thereby, production cost can be reduced.

The oriented superconducting layer 15 includes, for example, a DyBa ₂ Cu ₃ O _7-X superconducting material.
The oriented superconducting layer 15 contains 2.0 × 10 ^{16 to} 5.0 × 10 ¹⁹ atoms / cc of fluorine residue and 1.0 × 10 ^{18 to} 5.0 × 10 ²⁰ atoms / cc of residual carbon.
Area SS immediately below the portion oriented at a swing angle of 10 degrees or less in oriented superconducting layer 15 and area SO in contact with substrate 21 oriented at a swing angle of 10 degrees or less on the bottom surface of oriented superconducting layer 15 The area SO <0.3 × the area SS, that is, the area SO is less than 0.3 times the area SS. Preferably, the area SO is not more than 0.1 times the area SS. The thickness of the portion other than the region directly above the portion in contact with the substrate 21 in the oriented superconducting layer 15 is 1 micrometer (μm) or more. On the metal layer 22, the width of the oriented superconducting layer 15 in the direction parallel to the upper surface of the metal layer 22 is 1 micrometer (μm) or more, preferably 5 micrometers (μm) or more.

Claims (3)

An alignment portion is formed on a base, a solution containing metal trifluoroacetate is brought into contact with the alignment portion and a portion other than the alignment portion, and a metal contained in the metal trifluoroacetate on the base and Forming a gel film containing fluoride;
Heat-treating the base, and forming an oriented superconducting layer in which the orientation portion and any crystal axis are oriented on the orientation portion and a portion other than the orientation portion;
The manufacturing method of the oxide superconductor provided with. The method for producing an oxide superconductor according to claim 1, wherein the oriented portion is a single crystal of lanthanum aluminate (LaAlO ₃ ).   The method for producing an oxide superconductor according to claim 1, wherein the oriented portion is a ceramic fiber.