JP2017016841A - REBaxCuyOz-BASED SUPERCONDUCTING WIRE MATERIAL AND MANUFACTURING METHOD OF REBaxCuyOz-BASED SUPERCONDUCTING WIRE MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an RE-based oxide superconductive wire material having high superconductive property such as critical current density (Jc) of 0.3 MA/cmor more even under high magnetic environment of 3T or more.SOLUTION: There is provided an REBaCuO-based superconducting wire material having an REBaCuO-based superconducting layer. where RE represents at least one or more kind of element selected from a group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr and Ho and x=1.5 to 2.0, y=2.5 to 3.5, z=6.2 to 7.2, where oxide particles with 30 nm or less containing BA and addition element M, where M is at least one or more kind of element selected from Zr, Hf, Ir, Sn, Ce, Ti and Nb, are dispersed with occupying 40 to 70% of area when cutting the superconductive layer with 500 nm square and the superconducting layer is 1.5 μm.SELECTED DRAWING: Figure 2

Description

The present invention relates to a REBa _x Cu _y O _z system (RE represents one or more elements selected from Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho, and x = 1. 5 to 2.0, y = 2.5 to 3.5, z = 6.2 to 7.2.) The present invention relates to a superconducting wire and a method of manufacturing a superconducting wire.

REBa _x Cu _y O _z- based (also referred to as “REBCO-based”) oxide superconductors have a higher critical temperature (Tc) than conventional metal-based superconductors such as Nb ₃ Sn and Nb ₃ Al. Superconducting equipment such as transformers and motors can be operated at liquid nitrogen temperature. For this reason, research into making the wire has been vigorously conducted.

  As a superconducting application device to which superconducting wire is applied, superconducting wire has high superconducting characteristics (critical current density Jc, critical current value) for all magnetic field application angles in order to be used in superconducting devices used under an applied magnetic field. It is desirable to have Ic).

  For example, when a solenoid coil is formed of a superconducting wire, a magnetic field is applied at an angle at which the superconducting property Jc is reduced with respect to the substrate surface (superconducting surface) at both ends of the coil. It will be limited by the value. This is a big problem for application to power equipment such as superconducting transformers and SMES used under high magnetic fields.

  Further, in the superconductor in the superconducting wire, the density of the quantized magnetic flux that enters the superconductor increases with the increase of the applied magnetic field, and the superconducting state Jc is deteriorated due to the movement of these to break the superconducting state. Furthermore, the superconductor has a characteristic that Jc when a magnetic field is applied in the c-axis direction is lower than Jc when a magnetic field is applied in the a-axis direction due to the crystal structure.

  In order to prevent the movement of the quantized magnetic flux in the superconductor, it is expected that nano-size magnetic flux pinning points having an isotropic shape effective in any magnetic field direction are uniformly introduced into the superconductor at nanometer intervals. For this point, there is a technology that improves the magnetic field application angle dependency in a high magnetic field by introducing a uniform and fine magnetic flux pinning point in a superconductor with a thick film and excellent grain boundary characteristics and crystallinity. (See Patent Document 1).

Japanese Patent No. 5270176

  By the way, the superconducting oxide material including the magnetic flux pinning point manufactured by the conventional technique in the superconducting layer can obtain very excellent superconducting characteristics in a magnetic field of about 77K and 1T. However, the oxide superconducting wire manufactured by the conventional technique has a significant decrease in the critical current value Ic [A / cm] in a strong magnetic field higher than that, for example, a high magnetic field of 3 T or higher. Couldn't get.

  In other words, the superconducting properties deteriorate in a higher magnetic field environment, so even if the amount of addition of the magnetic flux pinning point is simply increased, the particle size at the magnetic flux pinning point will increase, and the superconducting property will be degraded. I understood.

Therefore, improvement of superconducting characteristics applicable to high magnetic fields, high superconductivity with a critical current density (Jc) of 0.3 MA / cm ² or higher at a stronger magnetic field of 77K, a magnetic field exceeding 1T, especially a high magnetic field of 3T or higher. There is a demand for production of superconducting wires having characteristics.

The present invention has been made in view of such a point. For example, a REBaCuO-based superconducting wire and a superconducting material having high superconducting properties such as a critical current density (Jc) of 0.3 MA / cm ² or more even in a high magnetic field environment of 3 T or more. It aims at providing the manufacturing method of a wire.

One aspect of the REBa _x Cu _y O _z -based superconducting wire of the present invention is a REBa _x Cu _y O _z (RE is Y, Nd, Sm, Gd, Dy, Eu, 1 represents at least one element selected from the group consisting of Er, Yb, Pr and Ho, x = 1.5 to 2.0, y = 2.5 to 3.5, z = 6.2 to 7 a .2. in) based REBa _x Cu _y O _z superconducting wire having a superconducting layer of, in the superconducting layer, so occupying 3～30Vol% in area when the superconducting layer was cut out with 500nm cubic In addition, oxide particles of 30 nm or less containing Ba and an additive element M (M is at least one element selected from Zr, Hf, Ir, Sn, Ce, Ti, and Nb) are dispersed as magnetic flux pinning points. The film thickness of the superconducting layer is 1.5 μm or less. Take the configuration that is above.

One aspect of the method for producing a REBa _x Cu _y O _z superconducting wire of the present invention includes a coating step of coating a raw material solution on a substrate via an intermediate layer, and subjecting the coated raw material solution to a calcining heat treatment. A preliminary firing step for producing a superconducting precursor, and a main firing treatment step for producing a superconducting layer by subjecting the superconducting precursor to a heat treatment. As the raw material solution, RE (RE is Y, Nd, Sm) , Gd, Dy, Eu, Er, Yb, Pr and Ho), Ba and an additive element M (M is Zr) in an organometallic complex solution containing Ba and Cu. , Hf, Ir, Sn, Ce, Ti, and Nb), and the coating process includes a film thickness of 1.5 μm or more in the main baking process. The superconducting layer is formed As described above, the application of the raw material solution having a single coating film thickness of 0.1 μm or less was repeated a plurality of times.

According to the present invention, high superconducting properties such as a critical current density (Jc) of 0.3 MA / cm ² or more can be obtained even in a high magnetic field environment of 3 T or more.

Schematic diagram showing an outline of REBa _x Cu _y O _z based oxide method of manufacturing a superconducting wire according to the present invention Schematic which shows the cross section perpendicular | vertical to the axial direction of the tape of the oxide superconducting wire manufactured with the manufacturing method of the oxide superconducting wire which concerns on embodiment of this invention. The figure which shows dispersion | distribution of the magnetic flux pinning point in the superconducting layer of the comparative example 1 The figure which shows dispersion | distribution of the magnetic flux pinning point in the superconducting layer of an Example

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

REBa _x Cu _y O _z system according to an embodiment of the present invention (RE represents one or more elements selected from Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr and Ho, x = 1.5-2.0, y = 2.5-3.5, z = 6.2-7.2.) A method for producing an oxide superconducting wire is a REBaCuO-based oxide including magnetic flux pinning. Regarding the production of a superconducting wire (hereinafter referred to as “RE-based superconducting wire”), specifically, in the MOD method, there is a feature in a coating process when generating a RE-based superconducting layer.

  FIG. 1 is a schematic diagram showing an outline of a method for producing a REBCO-based oxide superconducting wire according to the present invention.

First, the composite substrate 25 is formed by forming the intermediate layer 22 (see FIG. 2) on a tape-shaped substrate, for example, a Ni alloy substrate (base material). Specifically, a first intermediate layer made of Gd ₂ Zr ₂ O _{7 is formed} by sputtering as a template on a Ni alloy substrate (base material), and further, Y ₂ O _{3 is formed} thereon by sputtering. The second intermediate layer and the third intermediate layer made of MgO are sequentially formed by the IBAD method. Next, a fourth intermediate layer made of LaMnO ₃ is formed on the third intermediate layer by sputtering, and further a fifth intermediate layer made of CeO ₂ is formed thereon by sputtering or PLD. Thereby, the composite substrate 25 is formed (see FIG. 2).

  On this composite substrate 25, a coating solution is formed by applying a mixed solution (superconducting raw material solution) in coating step A. Here, the mixed solution is applied onto the composite substrate 25 by a dip coating method. For example, this mixed solution is prepared by mixing Y-TFA salt (trifluoroacetate salt), Ba-TFA salt and Cu-2-ethylhexanoate in an organic solvent with Y: Ba: Cu = 1: 1.5: 3. In addition to the mixed solution dissolved at a ratio, an additive element M such as Zr for forming a magnetic flux pinning point is added. Details of the mixed solution will be described later.

  The dip coating method is a method of applying the mixed solution to the surface of the substrate by immersing (immersing) the composite substrate 25 in a container in which the mixed solution is accommodated, and then pulling it up from the mixed solution. In the dip coating method, when the film is pulled up, the film thickness is adjusted by the pulling speed and the surface tension, density, and viscosity of the mixed solution, and the mixed solution is applied, that is, a coating film is formed. In the dip coating method, the film thickness can be controlled by the pulling speed of the substrate and the solution viscosity. The relationship between the substrate pulling speed and the film thickness applied to the substrate at the time of pulling is such that the lower the pulling speed is, the thinner the film is, and the higher the pulling speed is, the thicker the relationship is. Here, it is desirable that the viscosity of the mixed solution is 2 to 30 cP, and the moving speed of the base material in the dip coating method is in the range of 20 to 100 [m / h]. When the viscosity of the mixed solution is 2 to 30 cP and the moving speed of the substrate in the dip coating method is in the range of 20 to 100 [m / h], the mixed solution can be applied uniformly and thinly.

  Thus, after apply | coating a mixed solution, temporary baking is carried out by the temporary baking heat treatment process B. FIG. In the pre-baking heat treatment step B, for example, heating is performed by a heater or the like for a predetermined time in an atmosphere having a predetermined water vapor partial pressure and oxygen partial pressure. In the pre-baking heat treatment step B, the composite substrate 25 (see FIG. 2) is, for example, in a temperature range of 400 to 600 ° C. in an atmosphere of a water vapor partial pressure of 3 to 76 Torr and an oxygen partial pressure of 300 to 760 Torr in a baking apparatus. The calcination heat treatment is preferably performed.

  In addition, in the application step A, it is possible to use an inkjet method, a spray method, etc. in addition to the dip coating method described above, but basically, any process that can be applied on the composite substrate 25 a plurality of times in succession. It is not constrained by this example.

As described above, in the present embodiment, the film thickness that is applied once on the intermediate layer 22 (see FIG. 2) in the application step is 0.1 μm or less. Preferably, the coating film thickness at one time is not less than the particle diameter of the oxide particles containing Ba and the additive element M and not more than 0.05 μm. In the composite substrate 25, the intermediate layer formed on the base material may be formed by forming an intermediate layer made of CeO ₂ on the Gd ₂ Zr ₂ O ₇ intermediate layer. In this way, by controlling the film thickness to be applied once on the intermediate layer 22 (see FIG. 2) within the above range in the application step, the pinning points are uniformly dispersed in the applied layer.

  By repeating this coating step A and pre-baking heat treatment step B a predetermined number of times, the coating film is multi-coated on the intermediate layer of the composite substrate 25 of the tape-shaped oxide superconducting wire 20.

  In the present embodiment, the coating film thickness of 0.1 μm or less in which pinning points are uniformly dispersed is overlapped, that is, the coating film thickness is increased by repeating this coating, and the thickness of the superconducting wire to be manufactured is 1. The film thickness should be 5 μm or more.

  In this manner, a film body (“precursor” shown in FIG. 1) as an amorphous superconducting precursor to be a RE-based superconducting layer (hereinafter also referred to as “superconducting layer”) is formed on the intermediate layer in the composite substrate 25. To do.

  That is, the coating process A and the pre-baking heat treatment process B are applied at a film thickness of 0.1 μm or less at a time, and the pre-baking heat treatment is repeatedly performed, whereby the thickness of the superconducting layer to be manufactured is reduced. An amorphous precursor is formed so as to be 1.5 μm or more.

  After the amorphous precursor is formed in this manner, before the main baking heat treatment step D for performing the crystallization heat treatment, the intermediate baking is performed in the intermediate baking heat treatment step C at a temperature lower than the main baking heat treatment temperature in the main baking heat treatment step D. . The intermediate firing heat treatment is preferably performed on the amorphous precursor in a temperature range of 400 to 700 ° C. in an atmosphere having a water vapor partial pressure of 30 to 600 Torr and an oxygen partial pressure of 0.05 to 1 Torr.

  This intermediate baking heat treatment step C discharges residual organic components or residual fluoride in the calcination before reaching the crystallization temperature of REBCO. Next, in the main firing heat treatment step D, a heat treatment for crystallization of the superconducting precursor film body in the tape-shaped oxide superconducting wire 20, that is, a heat treatment for generating a RE-based superconducting layer is performed in water vapor gas.

  In the main baking heat treatment step D, a heat treatment for crystallizing the film body of the superconducting precursor, that is, heat treatment for generating a REBCO-based superconductor is performed. In the main baking heat treatment step C, for example, the composite substrate 25 is spirally wound around the peripheral surface of the cylinder, and the atmosphere of a predetermined partial pressure of water vapor and oxygen is obtained while rotating the cylinder in the baking apparatus. Inside, it is heated by a heater or the like for a predetermined time. In the main baking heat treatment step C, the main baking heat treatment is preferably performed in a temperature range of 700 to 900 ° C. in an atmosphere of a water vapor partial pressure of 30 to 600 Torr and an oxygen partial pressure of 0.05 to 1 Torr in a baking apparatus. The main heat treatment time is preferably 5 to 30 hours, more preferably 10 to 15 hours while introducing water vapor gas. In this main baking heat treatment, the precursor is heated at a temperature elevation temperature of 30 [° C./min].

  Thus, in the main baking heat treatment step D after the intermediate baking heat treatment step C, the RE-based superconducting layer in which the magnetic flux pinning points are uniformly dispersed and the magnetic field application characteristics are excellent can be formed.

  Then, after this main firing heat treatment step, a stabilization layer (for example, Ag stabilization layer) 24 (see FIG. 2) is applied on the superconducting layer of the generated superconducting wire by sputtering, and post-heat treatment is performed to obtain the superconducting wire. Manufacturing.

<Oxide superconducting wire>
FIG. 2 is a schematic view showing a cross section perpendicular to the axial direction of the tape of the oxide superconducting wire manufactured by the method of manufacturing an oxide superconducting wire according to the embodiment of the present invention.

  The oxide superconducting wire 20 has a tape shape, and an intermediate layer 22, a tape-shaped oxide superconducting layer (hereinafter referred to as "superconducting layer") 23, and a stabilization layer 24 are sequentially formed on a tape-shaped metal substrate 21. It is formed by being laminated. Here, the intermediate layer 22 includes a first intermediate layer 22a, a second intermediate layer 22b, a third intermediate layer 22c, a fourth intermediate layer 22d, and a fifth intermediate layer 22e.

  The tape-shaped metal substrate 21 is, for example, nickel (Ni), nickel alloy, stainless steel, or silver (Ag). Here, the metal substrate 21 is a crystal grain non-oriented, heat-resistant, high-strength metal substrate, and is Ni-Cr-based (specifically, Ni-Cr-Fe-Mo-based Hastelloy (registered trademark) B, C, X). Etc.), W-Mo series, Fe-Cr series (for example, austenitic stainless steel), Fe-Ni series (for example, non-magnetic composition type) and other materials such as cubic Vickers hardness (Hv ) = 150 or more nonmagnetic alloy. The thickness of the metal substrate 21 is, for example, 0.1 mm or less.

The first intermediate layer 22a is an uniaxially oriented intermediate layer in which Gd ₂ Zr ₂ O ₇ (GZO), yttrium-stabilized zirconia (YSZ), or the like is formed on the tape-shaped metal substrate 21 by sputtering. . The thickness of the first intermediate layer 22a is about 1000 nm. On the uniaxially oriented first intermediate layer 22a, a second intermediate layer 22b made of Y ₂ O ₃ is formed by sputtering. A third intermediate layer 22c made of MgO is formed on the second intermediate layer 22b by the IBAD method. A fourth intermediate layer 22d made of LaMnO ₃ is formed on the third intermediate layer 22c by sputtering. Further, here, CeO ₂ is vapor-deposited by a sputtering method (which may be PLD method) to form a fifth intermediate layer 22e as an omniaxial cap layer. The fifth intermediate layer 22e has a thickness of about 1000 nm. A superconducting layer 23 is formed on the fifth intermediate layer 22e. In the superconducting wire 20, the intermediate layer 22 is formed by the first intermediate layer 22a to the fifth intermediate layer 22e. An intermediate layer 22 is formed on these metal substrates 21 to form a composite substrate 25 shown in FIG. Note that the composite substrate 25 may have a biaxial orientation or may have a biaxial orientation intermediate layer 22 formed on a metal substrate 21 having no orientation. The intermediate layer 22 may be formed of one to three layers or six layers or more.

  On the superconducting layer 23, a stabilizing layer 24, which is a noble metal such as silver, gold, platinum, or an alloy thereof and is a low-resistance metal, is provided. The stabilization layer 24 is formed immediately above the superconducting layer 23 to prevent performance degradation caused by the reaction of the superconducting layer 23 with a noble metal such as gold or silver or a material other than an alloy thereof. To do. In addition to this, the stabilization layer 24 disperses heat generated by an accident current or alternating current to prevent destruction and performance degradation due to heat generation. The thickness of the stabilization layer 24 is 10-30 micrometers here.

The superconducting layer 23 is an all-axis oriented REBCO layer, that is, one or more selected from REBa _x Cu _y O _z (RE is selected from Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho. And x = 1.5 to 2.0, y = 2.5 to 3.5, and z = 6.2 to 7.2.). Here, the superconducting layer 23 is an yttrium-based oxide superconductor. The thickness of the superconducting layer 23 is 1.5 μm or more.

Here, the superconducting layer 23 contains the additive element M in the raw material solution composition RE: Ba: Cu = 1: 1.5: 3 used in the normal low Ba composition method in which the stoichiometric composition of Ba is less than 2. It is. The additive element M (M is at least one element selected from Zr, Hf, Ir, Sn, Ce, Ti, and Nb) is an artificial pin particle (magnetic flux) that is an effective oxide particle (for example, BaZrO ₃ ). Pinning point) 23a. The composition of the mixed solution at this time is set in consideration of the composition of the artificial pin particles (Ba: Zr = 1: 1 in the case of Zr).

  The oxide particles containing Ba and the additive element M, that is, the magnetic flux pinning points (artificial pinning points) 23a are oxide particles as a compound having a particle size of 30 nm or less uniformly dispersed in the superconducting layer 23. Note that the particle size of the magnetic flux pinning point 23a is more preferably within the above-mentioned range since the effect is better when the magnetic flux line size is closer to the magnetic flux line size. Here, the magnetic flux pinning points 23a have a particle size of 30 nm or less, and are uniformly dispersed so as to occupy 3 to 30 vol% in the region when the superconducting layer 23 is cut out in a 500 nm cube.

  The RE component in the mixed solution is composed of one or more types of RE salts of carboxylic acids having 3 to 8 carbon atoms that do not contain a ketone group. Here, the RE salt is preferably an RE salt of propionic acid, and is preferably yttrium propionate that does not contain a fluorine atom in the yttrium salt.

When the number of carbon atoms of propionic acid from which the RE salt is derived is smaller than 3, sufficient solubility cannot be obtained, and a uniform oxide superconducting thick film cannot be obtained. On the other hand, when the number of carbon atoms is larger than 8, the amount of CO ₂ gas generated during the pre-baking heat treatment increases, so that the coating film is likely to be scattered and it is difficult to obtain a high-quality oxide superconducting thick film.

Further, the Ba component in the mixed solution is barium trifluoroacetate represented by (CF ₃ COO) ₂ Ba · nH ₂ O (n is 0 or a hydration number that can be taken) and is usually an anhydride or 1 Obtained in hydrate. The use of trifluoroacetate as a precursor compound for the superconducting layer is conventionally known, but its advantage is that it does not pass through barium carbonate, which has a high conversion temperature to the superconducting layer.

The Cu component contained in the mixed solution is selected from the group consisting of a copper salt of a branched saturated aliphatic carboxylic acid having 6 to 16 carbon atoms and a copper salt of an alicyclic carboxylic acid having 6 to 16 carbon atoms. It consists of one or more types. The copper salt is L ² ₂ Cu · pH ₂ O (L ² is a branched saturated aliphatic carboxylic acid residue having 6 to 16 carbon atoms or an alicyclic carboxylic acid residue having 6 to 16 carbon atoms. , P is 0 or a hydration number that can be taken), and is usually obtained as an anhydrate or a 1-2 hydrate. Examples of the branched saturated aliphatic carboxylic acid having 6 to 16 carbon atoms from which the copper salt is derived include 2-ethylhexanoic acid, isononanoic acid, neodecanoic acid, and the like, and the number of carbon atoms from 6 to 16 from which the copper salt is derived. Examples of the derivative of the alicyclic carboxylic acid copper salt include cyclohexanecarboxylic acid, methylcyclohexanecarboxylic acid, and naphthenic acid. Among these carboxylic acids, those derived from natural products such as naphthenic acid may contain components other than the number of carbon atoms defined in the present invention or those having no branched or alicyclic groups as components. In the present invention, commercially available products can be used as they are, regardless of the presence or absence of these components.

  Here, the mixed solution contains Y-propionic acid, Ba-TFA, and Cu-2-ethylhexanoic acid as an RE salt of a carboxylic acid having 3 to 8 carbon atoms that does not contain a ketone group.

  As said copper salt, since the copper salt of synthetic carboxylic acids, such as copper neodecanoate, copper 2-ethylhexanoate, copper isononanoate, becomes stable in terms of performance and quality, it is preferable. Moreover, copper neodecanoate, copper 2-ethylhexanoate, copper isononanoate, and copper naphthenate have good solubility in their own organic solvents, and further, the solubility of the RE salt and barium salt according to the present invention. It is preferable because it also has an effect of improving.

  In the mixed solution, the total content of the RE component, Ba component and Cu component is preferably 10 to 60% by weight, more preferably 30 to 50% by weight, and the molar concentration (total of the three components) is as follows: 0.5-2.0 mol / L is preferable, More preferably, it is 0.7-1.5 mol / L.

  In the mixed solution, the RE component, the Ba component, and the Cu component are Ba in the range of a <2 when the molar ratio of RE, Ba, and Cu is Y: Ba: Cu = 1: a: 3. It contains so that it may become a molar ratio. In this case, in order to obtain a high critical current density Jc and a critical current value Ic, the Ba molar ratio in the raw material solution is preferably in the range of 1.0 ≦ a ≦ 1.8, more preferably the raw material solution. The Ba molar ratio in the range is 1.3 ≦ a ≦ 1.7.

  Thereby, the segregation of Ba can be suppressed, and as a result, the precipitation of Ba-based impurities at the grain boundaries is suppressed. Therefore, the generation of cracks is suppressed and the electrical connectivity between crystal grains is improved, the superconducting film is formed by the MOD method, and has a tape-shaped oxide superconducting wire that is more uniform and has excellent superconducting properties. An oxide superconducting wire can be easily manufactured.

  Further, the organic solvent in the mixed solution is not particularly limited as long as it dissolves at least the RE component among the above-mentioned RE component, Ba component and Cu component. Specifically, the organic solvent is arbitrarily selected in order to obtain desired performance such as coating performance, solubility, viscosity (5 to 30 Pa · s), dissolution stability, etc. Good.

  Examples of the organic solvent include alcohol solvents, diol solvents, ester solvents, ether solvents, aliphatic or alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, hydrocarbon solvents having a cyano group, and halogenated solvents. Aromatic hydrocarbon-based agents, other solvents and the like can be mentioned.

  Examples of alcohol solvents include methanol, ethanol, propanol, isopropanol, 1-butanol, isobutanol, 2-butanol, tertiary butanol, pentanol, isopentanol, 2-pentanol, neopentanol, tertiary pentanol, Hexanol, 2-hexanol, heptanol, 2-heptanol, octanol, 2-ethylhexanol, 2-octanol, cyclopentanol, cyclohexanol, cycloheptanol, methylcyclopentanol, methylcyclohexanol, methylcycloheptanol, benzyl alcohol , Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, Examples include ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, 2- (N, N-dimethylamino) ethanol, and 3 (N, N-dimethylamino) propanol. .

  Examples of the diol solvent include ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, isoprene glycol (3-methyl -1,3-butanediol), 1,2-hexanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol, octanediol (2-ethyl-1, 3-hexanediol), 2-butyl-2-ethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1, 4-cyclohexanedimethanol etc. are mentioned.

  Examples of ketone solvents include acetone, ethyl methyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl hexyl ketone, ethyl butyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, methyl amyl ketone, Examples include cyclohexanone and methylcyclohexanone.

  Examples of ester solvents include methyl formate, ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, 2 butyl acetate, 3 butyl acetate, amyl acetate, isoamyl acetate, 3 amyl acetate, and phenyl acetate , Methyl propionate, ethyl propionate, isopropyl propionate, butyl propionate, isobutyl propionate, 2 butyl propionate, 3 butyl propionate, amyl propionate, isoamyl propionate, 3 amyl propionate, phenyl propionate , Methyl 2-ethylhexanoate, ethyl 2-ethylhexanoate, propyl 2-ethylhexanoate, isopropyl 2-ethylhexanoate, butyl 2-ethylhexanoate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethoxypropyl Methyl pionate, ethyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether Acetate, ethylene glycol mono tert-butyl ether acetate, ethylene glycol monoisobutyl ether acetate, ethylene glycol mono tert-butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether Acetate, propylene glycol monoisopropyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol mono second butyl ether acetate, propylene glycol mono isobutyl ether acetate, propylene glycol mono tertiary butyl ether acetate, butylene glycol monomethyl ether acetate, butylene glycol monoethyl ether acetate , Butylene glycol monopropyl ether acetate, butylene glycol monoisopropyl ether acetate, butylene glycol monobutyl ether acetate, butylene glycol mono sec-butyl ether acetate, butylene glycol monoisobutyl ether acetate, butylene glycol mono-tert-butyl ether Examples include ether acetate, methyl acetoacetate, ethyl acetoacetate, methyl oxobutanoate, ethyl oxobutanoate, γ-lactone, dimethyl malonate, dimethyl succinate, propylene glycol diacetate, and δ-lactone.

  Examples of the ether solvent include tetrahydrofuran, tetrahydropyran, morpholine, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, triethylene glycol dimethyl ether, dibutyl ether, diethyl ether, dioxane and the like.

  Aliphatic or alicyclic hydrocarbon solvents include pentane, hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, heptane, octane, decalin, solvent naphtha, turpentine oil, D-limonene, pinene, mineral spirit, swazol # 310 (Cosmo Matsuyama Oil Co., Ltd., Solvesso # 100 (Exxon Chemical Co., Ltd.)) and the like.

  Examples of the aromatic hydrocarbon solvent include benzene, toluene, ethylbenzene, xylene, mesitylene, diethylbenzene, cumene, isobutylbenzene, cymene, and tetralin.

  Examples of the hydrocarbon solvent having a cyano group include acetonitrile, 1-cyanopropane, 1-cyanobutane, 1-cyanohexane, cyanocyclohexane, cyanobenzene, 1,3-dicyanopropane, 1,4-dicyanobutane, 1,6- Examples include dicyanohexane, 1,4-dicyanocyclohexane, 1,4-dicyanobenzene and the like.

  Examples of the halogenated aromatic hydrocarbon solvent include carbon tetrachloride, chloroform, trichloroethylene, and methylene chloride.

  Examples of other organic solvents include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, aniline, triethylamine, and pyridine.

  As the above-mentioned organic solvent, those having a boiling point of 80 ° C. or more are preferable because they give uniform coating properties. An alcohol solvent is preferable because it has good wettability to various substrates. 1-butanol, isobutanol, 2-butanol, tertiary butanol, pentanol, isopentanol, 2-pentanol, neopentanol, tertiary pentanol, hexanol, 2-hexanol, heptanol, 2-heptanol, octanol Alcohol solvents having 4 to 8 carbon atoms such as 2-ethylhexanol, 2-octanol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether are preferred.

  The content of the organic solvent in the mixed solution is 25 to 80% by weight. Considering coating property, metal component concentration, and dissolution stability, 40 to 70% by weight is preferable. The mixed solution further contains a solubilizer having an amino group in order to dissolve the propionate in the organic solvent. Examples of the amino group include tetramethylurea, n-octylamine, propylamine and the like. In particular, tetramethylurea is preferable because it is a high boiling point solvent.

  The organic solvent may contain optional components such as a leveling agent, a thickener, a stabilizer, a surfactant, and a dispersant. The content of these optional components is preferably 10% by weight or less in the mixed solution. Specific examples of the optional component include organic acids that function as a leveling agent. As the organic acid, an organic acid having 6 to 30 carbon atoms which may have a hydroxyl group, may have a branch, or may have an unsaturated bond is preferable. Specific examples include 2-ethylhexanoic acid, isononanoic acid, neodecanoic acid, undecanoic acid, lauric acid, tridecanoic acid, etc., myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid , Lignoceric acid, serotic acid, montanic acid, mellic acid, tocic acid, Linderic acid, tuzuic acid, palmitoleic acid, petrothelic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, γ-linolenic acid, Linolenic acid, ricinoleic acid, 12-hydroxystearic acid, cyclohexanecarboxylic acid, methylcyclohexanecarboxylic acid, naphthenic acid, rosinic acid, abietic acid and the like can be mentioned, and abietic acid is preferred.

  As described above, according to the present embodiment, the application step A for applying the raw material solution (mixed solution) onto the metal substrate 21 via the intermediate layer 22 and the applied mixed solution are subjected to the calcining heat treatment to obtain the superconducting precursor. A preliminary firing step B for generating a body, and a main firing treatment step D for forming a superconducting layer 23 by subjecting the superconductor precursor to a heat treatment. As a mixed solution, RE (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr and Ho), an organic metal containing Ba and Cu The complex solution has oxide particles containing Ba and an additive element M (M is at least one element selected from Zr, Hf, Ir, and Sn). In the coating process A, in the main baking process D, a single coating film thickness of 0.1 μm or less is repeatedly formed several times so as to form a superconducting layer 23 having a film thickness of 1.5 μm or more. .

Specifically, BaZrO ₃ , which is an oxide particle containing Ba and Zr contained in the superconducting layer 23, does not have a particle size larger than its thickness within a single coating film layer, but a single coating. It is uniformly distributed over the entire surface in the film layer. Since the superconducting layer 23 is formed by making this into multiple layers, the BaZrO ₃ that is the magnetic flux pinning points 23a contained in the superconducting layer 23 is distributed in layers in the thickness direction, and the superconducting layer 23 as a whole is substantially uniform 30 nm. It is dispersed in the state of being refined with the following particle size.

That is, in the superconducting layer 23 having a film thickness of 1.5 μm or more in the oxide superconducting wire 20, no matter where the superconducting layer 23 is cut out with a 500 nm cube, a magnetic flux pinning point composed of Ba and Zr as the additive element M (For example, BaZrO ₃ ) 23a has a particle size of 30 nm or less, and is controlled so as to occupy _{3 to} 30 vol% in the cut-out region and disperse substantially uniformly. Thereby, even in a high magnetic field environment of 3T or more, it has high superconducting characteristics such as a critical current density (Jc) of 0.3 MA / cm ² or more.

In the coating step A, a REBaCu (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho) is used. And applied to the composite substrate 25 (see FIG. 2). Since this mixed solution contains, as an RE component, an RE salt of a carboxylic acid having 3 to 8 carbon atoms not containing a ketone group as an essential component, in the coating step A, the mixed solution is applied to the substrate by a dip coating method. In the case of application, wettability can be improved as compared with the case of applying a mixed solution containing an RE salt containing a ketone group. For example, the RE component in the mixed solution according to the present embodiment is a propionate (hereinafter referred to as “propion solution”). When this mixed solution containing propion liquid is used, a conventional mixed solution containing 2-ethylhexane salt as a mixed solution containing a ketone group (hereinafter referred to as “ethylhexane liquid”) is used. Compared to difficult to dry. In other words, when dip-coating with an ethyl hexane solution as the RE component is easier to evaporate (easily fly) than when dip-coating with the propion solution (mixed solution) of the present embodiment.
For this reason, when the substrate is lifted after coating with ethyl hexane solution, the coating film on the substrate is dried in a shape swollen at both ends as viewed in the axial direction along with factors such as the surface tension and polarity of the mixed solution.

  On the other hand, in the present embodiment in which dip coating is performed with a propion solution, since it contains a solubilizing agent having an amino group, it is difficult to evaporate (not easily fly). For this reason, the coating film on the substrate pulled up by applying the propion liquid is dried in a state where both end portions and the central portion are coated as uniform film bodies as viewed in the axial direction.

Thus, also, as a RE component, a mixed solution of propionic acid _{(C 3} H 6 _{O 2)} salt as an essential component can reduce the amount of C than levulinic acid _{(C 5 H 8 O 3)} . Thereby, generation | occurrence | production of a carbon dioxide gas is reduced and crack generation can be reduced.

  The Ni alloy substrate may have a biaxial orientation or may have a biaxial orientation intermediate layer formed on a non-oriented metal substrate.

Thus, in the superconducting layer 23, Ba and the additive element M (M is Zr, Hf, Ir, Sn, Ce) so as to occupy 3 to 30 vol% in the region when the superconducting layer 23 is cut out in a 500 nm cube. In addition, oxide particles of 30 nm or less containing at least one element selected from Ti, Nb) are dispersed as magnetic flux pinning points 23a, and the film thickness of the superconducting layer 23 is 1.5 μm or more. REBa _x Cu _y O _{A z-} based superconducting wire (oxide superconductor) 20 is manufactured.

  The oxide superconductor formed in this way is used for wires, devices, or power equipment such as power cables, transformers, and current limiters.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

<Example 1>
In Example 1, a REBaCu-based oxide superconductor was formed on a tape-shaped substrate by the MOD method shown in FIG. 1 using the mixed solution of the present embodiment. The base material of this Example 1 has Hastelloy (registered trademark) as a substrate and Gd ₂ Zr ₂ O ₇ , Y ₂ O ₃ , MgO, LaMnO ₃ , and CeO ₂ in this order on the Hastelloy (registered trademark). And an intermediate layer formed by stacking. The mixed solution used in the dip coating method includes Y-propionic acid, Ba-TFA, Cu-2-ethylhexanoic acid that does not contain fluorine atoms, and Y-propionic acid, Ba-TFA, Cu-2-ethylhexanoic acid. And an organic solvent that dissolves the above components. In addition, the organic solvent includes a solubilizer having an amino group that dissolves propionic acid (here, tetramethylurea). The viscosity of the mixed solution was 15 Pa · s. In the dip coating method, the one-time coating film thickness of the superconductor was 0.1 μm / coat. This was repeated a plurality of times until the desired film thickness (here, the film thickness of the superconducting layer to be formed was 1.5 μm or more).

<Example 2>
When forming a YBCO superconductor by the MOD method in the same manner as in Example 1, compared with Example 1, the coating film thickness is set to 0.05 μm, and other conditions are the same as in Example 1. The mixed solution was applied.

<Example 3>
When a YBCO superconductor is formed by the MOD method as in Example 1, the coating film thickness is set to 0.03 μm once compared to Example 1, and the other conditions are the same as in Example 1. The mixed solution was applied.

<Comparative Example 1>
When a YBCO superconductor is formed by the MOD method in the same manner as in Example 1, the coating thickness is set to 0.15 μm once compared to Example 1, and other conditions are the same as in Example 1. The mixed solution was applied.

  Table 1 shows the measurement results of the critical current density Jc, which is the superconducting characteristic of the BC superconductor (oxide superconducting wire) formed by Examples 1 to 3 and Comparative Example 1.

FIG. 3 shows dispersion of magnetic flux pinning points in the superconducting layer, FIG. 3A is a diagram (image) showing a part of the superconducting layer in Comparative Example 1, and FIG. 3B shows an example (here, example) It is a figure (image) which cuts out and shows a part of superconducting layer in 3).
When Examples 1 to 3 and Comparative Example 1 were compared, Jc (min.) Was less than 0.3 when a single coating film thickness exceeded 0.1 μm. As shown in the image (cutout region) in FIG. 3A, this is considered to be caused not only by the fact that the particle diameter of the magnetic flux pinning BaZrO ₃ crystal exceeds 30 μm, but also because of its non-uniform distribution. On the other hand, if the coating film thickness was 0.1 μm or less as in Examples 1 to 3, a high Jc could be obtained. This is because, as shown in the image (cutout region) in FIG. 3B, the particle diameter of the magnetic flux pinning BaZrO ₃ crystal is not only 30 μm or less, but also the distribution is uniform. It was found that Jc (min.) Was even higher when the coating film thickness was 0.05 μm or less. This is due to the fact that the particle size of the magnetic flux pinning BaZrO ₃ crystal is not only 20 μm or less, but is more uniform with the distribution. Note that FIG. 3B shows a part of the superconducting layer of Example 3, which is cut out. Similarly, in Examples 1 and 2, the crystal of magnetic flux pinning BaZrO ₃ is 30 μm or less, and further along with its distribution. Is uniform.

  The embodiment of the present invention has been described above. The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this. That is, the description of the configuration of the apparatus and the shape of each part is an example, and it is obvious that various modifications and additions to these examples are possible within the scope of the present invention.

Method for producing a REBa _x Cu _y O _z superconducting wire and REBa _x Cu _y O _z superconducting wire according to the present invention, the critical current density in high magnetic field environment of more than 3T (Jc) 0.3MA / cm ² or more It has the effect of having such a high superconducting characteristic, and is useful when manufacturing an oxide superconducting wire by the MOD method.

20 Oxide superconducting wire 21 Metal substrate 22 Intermediate layer 23 Superconducting layer 23a Pinning point 24 Stabilizing layer 25 Composite substrate

Claims (8)

REBa _x Cu _y O _z formed on the substrate via an intermediate layer (RE is at least one selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho) X = 1.5-2.0, y = 2.5-3.5, z = 6.2-7.2) REBa _x Cu _y O _z having a superconducting layer In system superconducting wire,
In the superconducting layer, Ba and additive element M (M is Zr, Hf, Ir, Sn, Ce, Ti, so as to occupy 3 to 30 vol% in the region when the superconducting layer is cut out in a 500 nm cube. 30 nm or less oxide particles containing at least one element selected from Nb) are dispersed as magnetic flux pinning points,
The film thickness of the superconducting layer is 1.5 μm or more.
A REBa _x Cu _y O _z- based superconducting wire characterized by the above. The oxide particles are Zr.
REBa _x Cu _y O _z superconducting wire according to claim 1, wherein a. An application step of applying a raw material solution on a substrate via an intermediate layer, a calcination step of subjecting the applied raw material solution to a calcination heat treatment to generate a superconducting precursor, and a heat treatment of the superconducting precursor. A main baking treatment step for generating a superconducting layer,
As the raw material solution, an organic material containing RE (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho), Ba, and Cu. The metal complex solution has oxide particles containing Ba and an additive element M (M is at least one element selected from Zr, Hf, Ir, Sn, Ce, Ti, Nb),
In the coating step, a plurality of coatings of the raw material solution having a coating film thickness of 0.1 μm or less at a time so that the superconducting layer having a film thickness of 1.5 μm or more is formed in the main baking process step. Repeated times,
REBa _x Cu _y O _z based method of manufacturing a superconducting wire, characterized in that. Between the heat treatment of the calcining heat treatment step and the main baking heat treatment step, intermediate heat treatment is performed by maintaining a constant temperature at a temperature higher than the temperature of the calcining treatment and lower than the heat treatment temperature of the main baking heat treatment step.
REBa _x Cu _y O _z based method of manufacturing a superconducting wire according to claim 3, characterized in that. The oxide particles are 30 nm or less,
The method for producing a REBa _x Cu _y O _z- based superconducting wire according to claim 3 or 4. The oxide particles are 20 nm or less,
REBa _x Cu _y O _z based method of manufacturing a superconducting wire according to any one of claims 3 to 5, characterized in that. The organometallic complex solution is an RE salt of a carboxylic acid having 3 to 8 carbon atoms not containing a ketone group as an RE component, a barium trifluoroacetate as a Ba component, and a branch having 6 to 16 carbon atoms as a Cu component. One or more types of copper salts selected from the group consisting of copper salts of saturated aliphatic carboxylic acids and copper salts of alicyclic carboxylic acids having 6 to 16 carbon atoms, and an organic solvent for dissolving these metal salt components, As an essential component,
REBa _x Cu _y O _z based method of manufacturing a superconducting wire according to any one of claims 3 to 6, characterized in that. The RE component comprises a propionate containing no fluorine atom,
REBa _x Cu _y O _z based method of manufacturing a superconducting wire according to any one of claims 3 to 7, characterized in that.