Raw material solution, method for producing oxide superconducting material, superconducting wire material, and device

Abstract

This raw material solution is for use in production of an oxide superconducting material using a coating pyrolysis method. The raw material solution contains, as a solute, a carboxylic acid rare earth salt, a carboxylic acid barium salt, and a carboxylic acid copper salt, and contains, as a solvent, water, an alcohol having 1-4 carbon atoms, and a carboxylic acid having 1-4 carbon atoms. In the solvent, the water is contained in an amount of 0.01-35 vol%, the alcohol is contained in an amount of 45-99.99 vol%, and the carboxylic acid is contained in an amount of 20 vol% or less.

Description

Raw material solution, method for producing oxide superconducting material, superconducting wire, and device

[0001] The present disclosure relates to a raw material solution, a method for producing an oxide superconducting material, a superconducting wire, and an apparatus. This application claims priority to Japanese Patent Application No. 2024-032532, filed on March 4, 2024. The entire contents of this Japanese patent application are incorporated herein by reference.

[0002] One known method for producing oxide superconducting materials is the coating pyrolysis method (Metal Organic Decomposition, hereinafter also referred to as the "MOD method"). Compared to gas phase methods (such as evaporation, sputtering, and pulsed laser deposition) that mainly use a vacuum, the MOD method has advantageous features as a method for producing superconducting materials, such as simpler production equipment and ease of handling large areas and complex shapes. JP 2012-012247 A (Patent Document 1) and WO 2023 / 033117 (Patent Document 2) disclose raw material solutions used in the production of oxide superconducting materials using the MOD method, and methods for producing oxide superconducting materials using the same.

[0003] JP 2012-012247 A International Publication No. 2023 / 033117

[0004] A raw material solution according to one embodiment of the present disclosure is a raw material solution used in producing an oxide superconductor material using a coating pyrolysis method. The raw material solution contains a rare earth carboxylate salt, a barium carboxylate salt, and a copper carboxylate salt as solutes, and water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms as solvents. In the solvent, the water is contained in an amount of 0.01 to 35% by volume, the alcohol is contained in an amount of 45 to 99.99% by volume, and the carboxylic acid is contained in an amount of 20% by volume or less.

[0005] Fig. 1 is a flowchart showing an example of a method for producing an oxide superconducting material according to one embodiment of the present disclosure. Fig. 2 is a flowchart showing another example of a method for producing an oxide superconducting material according to one embodiment of the present disclosure. Fig. 3 is an explanatory diagram showing an example of a superconducting wire according to one embodiment of the present disclosure. Fig. 4 is an explanatory diagram showing a nuclear magnetic resonance apparatus as an example of an apparatus according to one embodiment of the present disclosure.

[0006] [Problem to be Solved by the Present Disclosure] From the viewpoint of efficiently producing oxide superconducting materials, there is a demand for lower temperatures and shorter times during heat treatment compared to the production methods disclosed in Patent Documents 1 and 2. In view of the above circumstances, an object of the present disclosure is to provide a raw material solution that can efficiently produce oxide superconducting materials, a method for producing oxide superconducting materials using the same, a superconducting wire obtained by the same, and an apparatus including the superconducting wire.

[0007] [Effects of the Present Disclosure] According to the present disclosure, there are provided a raw material solution capable of efficiently producing an oxide superconducting material, a method for producing an oxide superconducting material using the raw material solution, a superconducting wire obtained by the method, and an apparatus including the superconducting wire.

[0008] [Description of Embodiments of the Present Disclosure] The present inventors have conducted extensive research to solve the above-mentioned problems and have arrived at the present disclosure. The present inventors have focused on the solvent contained in a raw material solution used in producing an oxide superconductor using the MOD method. As a result, they have discovered the composition of the solvent that allows an oxide superconductor to be obtained from a calcined film formed by applying the raw material solution to a substrate and calcining it under heat treatment conditions of low temperature and short time, and have completed the present disclosure.

[0009] First, embodiments of the present disclosure will be described. [1] A raw material solution according to one aspect of the present disclosure is a raw material solution used in producing an oxide superconductor using a coating pyrolysis method. The raw material solution contains a rare earth carboxylate salt, a barium carboxylate salt, and a copper carboxylate salt as solutes, and water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms as solvents. The water content of the solvent is 0.01 to 35 vol%, the alcohol content is 45 to 99.99 vol%, and the carboxylic acid content is 20 vol% or less. A raw material solution having these characteristics has a solvent composition that allows an oxide superconductor to be obtained from a calcined film formed by coating the raw material solution on a substrate and calcining it under heat treatment conditions of low temperature and short time. Therefore, the raw material solution can efficiently provide an oxide superconductor.

[0010] [2] In the raw material solution according to [1], at least one of the rare earth carboxylate salt, the barium carboxylate salt, and the copper carboxylate salt may be a salt of a monocarboxylic acid having a carbon number of 1 to 4. In this case, an oxide superconducting material can be obtained more efficiently.

[0011] [3] A raw material solution according to one embodiment of the present disclosure is a raw material solution used in the production of an oxide superconducting material using a coating pyrolysis method. The raw material solution contains a composite oxide as a solute, and water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms as a solvent. In the solvent, the water is contained in an amount of 0.01 to 35% by volume, the alcohol is contained in an amount of 45 to 99.99% by volume, and the carboxylic acid is contained in an amount of 20% by volume or less. The composite oxide is a compound having a structure such as RE ｘ Ba ｙ Cu ｚ O １５－δThe raw material solution is represented by the chemical formula: where x is 0.7 or more and 2.1 or less. y is 1.8 or more and 4.2 or less. z is 2.7 or more and 7.3 or less. δ is 0 or more and 8.5 or less. A raw material solution having these characteristics has a solvent composition that allows an oxide superconductor to be obtained from a calcined film formed by applying the raw material solution to a substrate and calcining it under heat treatment conditions of low temperature and short time. In addition, since the solute of the raw material solution is an oxide superconducting material, an oxide superconducting material with a more uniform atomic ratio can be obtained. Therefore, the raw material solution can efficiently provide a high-quality oxide superconducting material.

[0012] [4] In the raw material solution according to any one of [1] to [3], the solvent does not need to contain a basic organic solvent. This raw material solution has a solvent composition that allows an oxide superconductor to be obtained under heat treatment conditions of low temperature and short time, and therefore, an oxide superconductor can be obtained more efficiently.

[0013] [5] In the raw material solution according to any one of [1] to [4], the solvent may contain, as the carboxylic acid, a monocarboxylic acid having from 2 to 3 carbon atoms. In this case, an oxide superconducting material can be obtained more efficiently.

[0014] [6] In the raw material solution according to any one of [1] to [5], the solvent may contain propionic acid and acetic acid as the carboxylic acid. In this case, an oxide superconducting material can be obtained more efficiently.

[0015] [7] In the raw material solution according to any one of [1] to [6], the alcohol may be of two or more types. In this case, an oxide superconducting material can be obtained more efficiently.

[0016] [8] In the raw material solution according to [7], the alcohols may each have an equal volume. In this case, an oxide superconducting material can be obtained more efficiently.

[0017] [9] In the raw material solution according to any one of [1] to [8], the alcohol may contain an alcohol having a carbon number of 1 to 2 and an alcohol having a carbon number of 3 to 4. In this case, an oxide superconducting material can be obtained more efficiently.

[0018]

[10] In the raw material solution according to [9], the volume ratio of the alcohol having 1 to 2 carbon atoms to the alcohol having 3 to 4 carbon atoms may be within a range of 5:1 to 1:5. In this case, an oxide superconductor can be obtained more efficiently.

[0019]

[11] A method for producing an oxide superconducting material according to one embodiment of the present disclosure includes the steps of preparing a raw material solution, applying the raw material solution to a substrate to form a coating film, heating the coating film to thermally decompose a solute-derived compound in the coating film to form a calcined film, and heating the calcined film to form an oxide superconducting material. The solute-derived compound is a solute contained in the raw material solution. The raw material solution contains, as the solute, a rare earth carboxylate salt, a barium carboxylate salt, and a copper carboxylate salt, and, as a solvent, water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms. In the solvent, the water is contained in an amount of 0.01 to 35% by volume, the alcohol is contained in an amount of 45 to 99.99% by volume, and the carboxylic acid is contained in an amount of 20% by volume or less.

[0020] The method for producing an oxide superconductor having these characteristics can produce an oxide superconductor under heat treatment conditions of low temperature and short time in the step of forming the oxide superconductor, and therefore the method for producing an oxide superconductor can efficiently produce an oxide superconductor.

[0021]

[12] A method for producing an oxide superconducting material according to one embodiment of the present disclosure includes the steps of preparing a raw material solution, applying the raw material solution to a substrate to form a coating film, heating the coating film to thermally decompose a solute-derived compound in the coating film to form a calcined film, and heating the calcined film to form an oxide superconducting material. The solute-derived compound is a solute contained in the raw material solution. The raw material solution contains a complex oxide as the solute, and water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms as a solvent. In the solvent, the water is contained at 0.01% by volume or more and 35% by volume or less, the alcohol is contained at 45% by volume or more and 99.99% by volume or less, and the carboxylic acid is contained at 20% by volume or less. The complex oxide is a compound selected from the group consisting of RE, ｘ Ba ｙ Cu ｚ O １５－δ The formula is: where x is 0.7 or more and 2.1 or less, y is 1.8 or more and 4.2 or less, and z is 2.7 or more and 7.3 or less. δ is 0 or more and 8.5 or less. The step of preparing the raw material solution includes a step of obtaining a precursor solution by dissolving the solute in the carboxylic acid, a step of obtaining a dried product by drying the precursor solution, and a step of obtaining the dried product in the liquid containing the alcohol to obtain the raw material solution.

[0022] The method for producing an oxide superconductor having these characteristics can produce an oxide superconductor under heat treatment conditions of low temperature and short time in the step of forming the oxide superconductor. In addition, the method for producing an oxide superconductor can produce an oxide superconductor with a more uniform atomic ratio because the solute of the raw material solution is an oxide superconductor. Therefore, the method for producing an oxide superconductor can efficiently produce a high-quality oxide superconductor.

[0023]

[13] The method for producing an oxide superconductor according to

[11] or

[12] may further include a step of filtering the raw material solution after the step of preparing the raw material solution and before the step of forming the coating film. In this case, by removing insoluble impurities in the raw material solution, a higher quality oxide superconductor can be obtained.

[0024]

[14] The oxide superconducting material produced using the raw material solution according to any one of [1] to

[10] may be used to produce a superconducting wire. The superconducting wire may be a superconducting coil, a superconducting cable conductor, a superconducting junction, a nuclear magnetic resonance apparatus, a nuclear magnetic resonance imaging apparatus, or a superconducting wire included in a nuclear fusion reactor. In this case, superconducting wires useful for various applications can be efficiently produced.

[0025]

[15] A superconducting wire according to one aspect of the present disclosure includes the oxide superconducting material produced using the raw material solution according to any one of [1] to

[10] . A superconducting wire having such characteristics can be efficiently produced because it includes the oxide superconducting material that can be efficiently produced from the raw material solution.

[0026]

[16] A device according to one aspect of the present disclosure includes the superconducting wire according to

[15] . A device having such characteristics can be efficiently manufactured using the superconducting wire.

[0027] [Details of Embodiments of the Present Disclosure] Specific examples of several embodiments of the present disclosure (raw material solutions, methods for producing oxide superconducting materials using the same, superconducting wires obtained thereby, and devices including the superconducting wires) will be described below with reference to the drawings, etc. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts.

[0028] In this specification, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and only a unit is specified for B, the unit of A and the unit of B are the same. In this specification, when a compound or the like is expressed by a chemical formula, the compound is considered to include any conventionally known atomic ratio unless the atomic ratio is particularly limited, and is not necessarily limited to only the atomic ratio within a stoichiometric range.

[0029] As used herein, the term "solute" refers to a substance that is dissolved in a solvent to form a solution, or in other words, the starting material. As used herein, the term "solvent" refers to a liquid that dissolves the solute. As used herein, the term "solution" refers to a mixture having a uniform phase that is formed by dissolving the solute in the solvent.

[0030] [First Embodiment: Raw Material Solution Containing Rare Earth Carboxylate, Barium Carboxylate, and Copper Carboxylate as Solutes] The raw material solution according to the first embodiment is a raw material solution used in the production of an oxide superconductor using a coating pyrolysis method (MOD method). The raw material solution contains a rare earth carboxylate, a barium carboxylate, and a copper carboxylate as solutes, and water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms as solvents. The water content of the solvent is 0.01 to 35 vol%, the alcohol content is 45 to 99.99 vol%, and the carboxylic acid content is 20 vol% or less. In particular, the solvent does not need to contain a basic organic solvent. A raw material solution having these characteristics has a solvent composition that allows an oxide superconductor to be obtained from a calcined film formed by coating the raw material solution on a substrate and calcining it under heat treatment conditions of low temperature and short time. Therefore, the raw material solution can efficiently provide an oxide superconductor.

[0031] The raw material solution according to the first embodiment is a raw material solution used in the production of oxide superconductors using the MOD method, as described above. The inventors aimed to efficiently produce oxide superconductors using the MOD method and attempted to create a raw material solution that would enable heat treatment of a coating film (calcined film) at a lower temperature and in a shorter time. As a result, it was discovered that the above-mentioned problem could be solved by a raw material solution containing a solvent having the above-mentioned composition. The inventors believe that the main reason the above-mentioned problem could be solved is that the raw material solution does not contain a basic organic solvent such as pyridine.

[0032] This is because, in order to efficiently produce a high-quality oxide superconductor using the MOD method, it has been conventionally believed that pH adjustment of the raw material solution by adding a basic organic solvent (specifically, neutralization of a carboxylic acid having 1 to 4 carbon atoms contained in the solvent) is necessary. In this case, the basic organic solvent must be removed during heat treatment, resulting in high-temperature and long-term heat treatment conditions. On the other hand, the present inventors have discovered that a solvent having the above-described composition is not highly acidic, and therefore a high-quality oxide superconductor can be efficiently produced without using the basic organic solvent and without pH adjustment of the raw material solution. As shown in the examples described below, it has been confirmed that a coating film (calcined film) formed from the raw material solution according to the present disclosure can efficiently produce a high-quality oxide superconductor even when heat-treated at a lower temperature and for a shorter time than conventional methods.

[0033] The basic organic solvent has conventionally been added for the purpose of neutralizing carboxylic acids having 1 to 4 carbon atoms (for example, formic acid has a pKa of 3.75, acetic acid has a pKa of 4.76, propionic acid has a pKa of 4.87, and butyric acid has a pKa of 4.82), as described above. For this purpose, the basic organic solvent may be a compound whose conjugate acid has a pKa of 5 to 14, and specifically may be an organic compound containing a nitrogen atom, such as pyridine whose conjugate acid has a pKa of 5.25 or ethylenediamine whose conjugate acid has a pKa of 10.7.

[0034] <Solute> At least one of the rare earth carboxylate, barium carboxylate, and copper carboxylate may be a salt of a carboxylic acid having 1 to 4 carbon atoms. Such a salt of a carboxylic acid has high solubility and dissolution stability in a solvent. The solute of the raw material solution is a carboxylate, not an acetylacetonate. Therefore, multi-stage processes and precise control are not required when preparing the raw material solution.

[0035] From the viewpoint of high solubility in a solvent and high dissolution stability, the rare earth carboxylate, the barium carboxylate, and the copper carboxylate may be salts of a carboxylic acid having 2 or more and 3 or less carbon atoms.

[0036] From the viewpoint of high solubility in a solvent and high dissolution stability, at least one of the rare earth carboxylate, the barium carboxylate, and the copper carboxylate may be a salt of a monocarboxylic acid having from 1 to 4 carbon atoms. Examples of the salt of a monocarboxylic acid having from 1 to 4 carbon atoms include formates, acetates, propionates, and butyrates.

[0037] From the viewpoint of high solubility in a solvent and high dissolution stability, at least one of the rare earth carboxylate, the barium carboxylate, and the copper carboxylate may be a salt of a dicarboxylic acid having from 2 to 4 carbon atoms. Examples of the salt of a dicarboxylic acid having from 2 to 4 carbon atoms include oxalates, malonates, and succinates.

[0038] The rare earth element constituting the rare earth carboxylate salt can be used without any particular limitation. Any rare earth element that can be used to produce a high-quality oxide superconducting material can be used without any particular limitation. The rare earth element constituting the rare earth carboxylate salt is, for example, at least one element selected from the group consisting of Y (yttrium), La (lanthanum), Pr (praseodymium), Nd (neodymium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0039] The molar ratio of rare earth (RE), barium (Ba), and copper (Cu) in each carboxylic acid salt contained in the solute may be the stoichiometric ratio of the oxide superconducting material to be produced or a ratio close to the stoichiometric ratio. ｘ Ba ｙ Cu ｚ O １５－δ In this case, x is 0.7 or more and 2.1 or less, y is 1.8 or more and 4.2 or less, z is 2.7 or more and 7.3 or less, and δ is 0 or more and 8.5 or less. The oxide superconducting material is typically a material containing RE １ Ba ２ Cu ３ O ７ , R.E.１ Ba ２ Cu ４ O ８ , or R.E. ２ Ba ４ Cu ７ O １５ The oxide superconducting material may be, for example, RE ｘ Ba ｙ Cu ｚ O ７ When a superconducting material (so-called RE123 superconducting material) is produced, the RE carboxylate, the Ba carboxylate, and the Cu carboxylate contained in the raw material solution may have a molar ratio of RE:Ba:Cu of 1±0.1:2±0.2:3±0.3. The molar ratio may be 1±0.05:2±0.10:3±0.15 or 1:2:3.

[0040] From the viewpoint of producing a high-quality oxide superconducting material, Cl (chlorine) may be added to the raw material solution. The Cl source to be added is, for example, an organic chlorine compound such as trichloroacetic acid, hydrochloric acid, ammonium chloride, etc. The raw material solution to which Cl has been added is calcined to produce CuCl (melting point 430°C), CuCl ２ (melting point 498°C). These chlorides become molten when the oxide superconductor constituting the oxide superconducting material is crystallized during firing (for example, at 740 to 760°C), and do not inhibit the c-axis orientation of the crystals of the oxide superconductor. This improves the quality of the oxide superconducting material, by increasing its superconducting properties such as critical current density Jc and critical current Ic.

[0041] <Solute Concentration in Raw Material Solution> The solute concentration in the raw material solution is not particularly limited, but may be 1.0 mol / L or more from the viewpoint of efficiently producing a high-quality oxide superconducting material, and may be 1.5 mol / L or less in consideration of the solubility of the solute in the raw material solution. The raw material solution may be appropriately diluted with a solvent to adjust the solute concentration in the solution to 0.1 mol / L or more and 1.5 mol / L or less, in accordance with the coating process in the method for producing an oxide superconducting material described below. In this specification, the "solute concentration in the solution" refers to the total metal ion concentration contained in the solvent.

[0042] <Solvent> The raw material solution contains, as a solvent, water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms.

[0043] (Water) Water can increase the solubility and dissolution stability of the solute, particularly increasing the dissolution stability. Therefore, water can prevent the precipitation of the solute from the raw material solution. There are no particular restrictions on the water that can be used in the raw material solution as long as it can produce an oxide superconducting material. However, the water used in the raw material solution may have a resistivity of 1 MΩ cm or more. Examples of such water include ion-exchanged water, distilled water, and RO (reverse osmosis) water.

[0044] (Alcohols with a carbon number of 1 to 4) Alcohols with a carbon number of 1 to 4 increase the solubility of the solute and also increase the wettability of the precursor solution to the substrate. Generally, the smaller the carbon number of the alcohol, the higher the solubility of the solute, and the larger the carbon number of the alcohol, the higher the wettability of the precursor solution to the substrate.

[0045] The alcohol may be of two or more types. For example, the alcohol may include an alcohol having 1 to 2 carbon atoms and an alcohol having 3 to 4 carbon atoms. The alcohol having 1 to 2 carbon atoms increases the solubility of the solute, and the alcohol having 3 to 4 carbon atoms increases the wettability of the precursor solution to the substrate. When the solvent contains two or more types of alcohol having 1 to 4 carbon atoms, the solubility of the solute and the wettability of the precursor solution to the substrate can be increased and adjusted. When the alcohol contains two or more types, each of the alcohols may have the same volume.

[0046] Examples of alcohols having 1 to 2 carbon atoms include methanol and ethanol. Examples of alcohols having 3 to 4 carbon atoms include 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol (also called 2-methylpropan-1-ol or 2-methylpropyl alcohol), and tert-butyl alcohol (also called 2-methyl-2-propanol).

[0047] The alcohols may include alcohols having one carbon atom and alcohols having four carbon atoms, such as methanol and 1-butanol or 2-butanol.

[0048] The volume ratio of the alcohol having 1 to 2 carbon atoms to the alcohol having 3 to 4 carbon atoms may be within a range of 5:1 to 1:5. By setting the volume ratio within a range of 5:1 to 1:5, it is possible to achieve a good balance between the solubility of the solute and the wettability of the precursor solution to the substrate. The volume ratio of the alcohol having 1 to 2 carbon atoms to the alcohol having 3 to 4 carbon atoms may be within a range of 4:1 to 1:4.

[0049] (Carboxylic Acid Having 1 or More and 4 or Less Carbon Amount) A carboxylic acid having 1 or more and 4 or less carbon atoms can increase the solubility of a solute. A carboxylic acid having 1 or more and 4 or less carbon atoms can also increase the dissolution stability of a solute. This is because when the solutes, RE carboxylic acid salt, Ba carboxylic acid salt, and Cu carboxylic acid salt, are all salts of a carboxylic acid having 1 or more and 4 or less carbon atoms, the ligands of RE, Ba, and Cu in the solute all become carboxylates having 1 or more and 4 or less carbon atoms before and after substitution, and there is no change or only a small change in the coordination species.

[0050] Examples of carboxylic acids having 1 to 4 carbon atoms include monocarboxylic acids and dicarboxylic acids. Examples of monocarboxylic acids having 1 to 4 carbon atoms include formic acid, acetic acid, propionic acid, and butyric acid. Examples of dicarboxylic acids having 1 to 4 carbon atoms include oxalic acid, malonic acid, and succinic acid.

[0051] The solvent may contain, as the carboxylic acid, a monocarboxylic acid having from 2 to 3 carbon atoms. In this case, when the solutes, i.e., the RE carboxylic acid salt, the Ba carboxylic acid salt, and the Cu carboxylic acid salt, are salts of a carboxylic acid having from 2 to 3 carbon atoms, the ligands of RE, Ba, and Cu in the solute all become carboxylates having from 2 to 3 carbon atoms before and after the substitution, and there may be no change in the coordination species or only a very small change. The solvent may contain, as the carboxylic acid, propionic acid and acetic acid.

[0052] (Proportions of Components in the Solvent) The solvent contains 0.01% by volume or more and 35% by volume or less of the water, 45% by volume or more and 99.99% by volume or less of the alcohol, and 20% by volume or less of the carboxylic acid. The solvent may consist of water and an alcohol. The solvent may consist of water, an alcohol, and a carboxylic acid. In other words, the raw material solution may not contain the carboxylic acid as the solvent. The carboxylic acid may be 0% by volume or more and 20% by volume or less. Furthermore, the carboxylic acid may be 0.1% by volume or more and 20% by volume or less. A solvent having such a composition eliminates the need to add a basic organic solvent to the raw material solution and enables the production of an oxide superconductor under heat treatment conditions of low temperature and short time. In other words, the solvent does not need to contain a basic organic solvent. Furthermore, a solvent having the above composition has the advantages of high solubility and dissolution stability of solutes and enhancing the wettability of the raw material solution to the substrate. When the solvent contains two or more types of alcohol, the range of 45% by volume or more and 99.99% by volume or less refers to the total amount of the two or more types of alcohol.

[0053] The solvent may have the following composition (A) or (B): (A) The water is contained in an amount of 5% by volume or more and 34% by volume or less, the alcohol is contained in an amount of 46% by volume or more and 95% by volume or less, and the carboxylic acid is contained in an amount of 0% by volume or more and 20% by volume or less; or (B) The water is contained in an amount of 18% by volume or more and 34% by volume or less, the alcohol is contained in an amount of 32% by volume or more and 95% by volume or less, and the carboxylic acid is contained in an amount of 0% by volume or more and 20% by volume or less.

[0054] When the solvent consists of water and alcohol, it may have the following composition (C), (D), or (E): (C) The water is contained in an amount of 0.01 vol% to 35 vol% and the alcohol is contained in an amount of 65 vol% to 99.99 vol%. (D) The water is contained in an amount of 0.01 vol% to 16.6 vol% and the alcohol is contained in an amount of 83.4 vol% to 99.99 vol%. (E) The water is contained in an amount of 16.8 vol% to 35 vol% and the alcohol is contained in an amount of 65 vol% to 83.2 vol%.

[0055] When the solvent consists of water, an alcohol, and a carboxylic acid, it may have the following composition (F), (G), or (H): (F) The water is contained in an amount of 0.01 vol% to 35 vol%, the alcohol is contained in an amount of 53 vol% to 99.89 vol%, and the carboxylic acid is contained in an amount of 0.1 vol% to 12 vol%; (G) The water is contained in an amount of 0.01 vol% to 35 vol%, the alcohol is contained in an amount of 55 vol% to 99.89 vol%, and the carboxylic acid is contained in an amount of 0.1 vol% to 10 vol%; (H) The water is contained in an amount of 0.01 vol% to 16.6 vol%, the alcohol is contained in an amount of 81.7 vol% to 99.89 vol%, and the carboxylic acid is contained in an amount of 0.1 vol% to 5.0 vol%.

[0056] When the solvent contains the carboxylic acid, the carboxylic acid may be contained in an amount of 0.1% by volume to 12% by volume, 0.1% by volume to 10% by volume, or 0.1% by volume to 5.0% by volume. The smaller the content of the carboxylic acid, the more likely it is that a calcined film will be formed stably.

[0057] When the carboxylic acid includes propionic acid and acetic acid, the propionic acid may be contained in an amount of more than 0 vol% and not more than 10 vol%, the acetic acid may be contained in an amount of more than 0 vol% and not more than 10 vol%, the propionic acid may be contained in an amount of 0.1 vol% or more and 5.0 vol% or less, and the acetic acid may be contained in an amount of 0.1 vol% or more and 5.0 vol% or less.

[0058] [Second embodiment: raw material solution containing complex oxide as solute] The raw material solution according to the second embodiment is a raw material solution used in the production of an oxide superconducting material using the MOD method. The raw material solution contains a complex oxide as a solute, and water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms as a solvent. In the solvent, the water is contained in an amount of 0.01 to 35% by volume, the alcohol is contained in an amount of 45 to 99.99% by volume, and the carboxylic acid is contained in an amount of 20% by volume or less. The complex oxide is a compound having a structure similar to RE ｘ Ba ｙ Cu ｚ O １５－δ The raw material solution is represented by the chemical formula: where x is 0.7 or more and 2.1 or less. y is 1.8 or more and 4.2 or less. z is 2.7 or more and 7.3 or less. δ is 0 or more and 8.5 or less. In particular, the solvent does not need to contain a basic organic solvent. A raw material solution having these characteristics has a solvent composition that allows an oxide superconductor to be obtained from a calcined film formed by applying the raw material solution to a substrate and calcining it under heat treatment conditions of low temperature and short time. Therefore, the raw material solution can efficiently provide an oxide superconductor.

[0059] Additionally, the raw material solution according to the second embodiment uses an oxide superconducting material as the solute, thereby enabling the production of an oxide superconducting material with a more uniform atomic ratio. To obtain a high-quality oxide superconducting material, the raw material solution according to the first embodiment requires that the rare-earth carboxylate salt, barium carboxylate salt, and copper carboxylate salt be dissolved in the solvent at appropriately controlled ratios so as to achieve a more uniform atomic ratio as the solute. To meet this requirement, the practitioner may be required to have some level of proficiency. The raw material solution according to the second embodiment uses an oxide superconducting material as the solute, thereby achieving a more uniform atomic ratio as the solute. Therefore, it is presumed that the practitioner does not require (or the level of proficiency is reduced). Therefore, the raw material solution according to the second embodiment can provide a high-quality oxide superconducting material particularly efficiently.

[0060] The raw material solution according to the second embodiment is the same as the raw material solution according to the first embodiment, except for the difference in the characteristics of the solute contained in the raw material solution. Therefore, the solute contained in the raw material solution according to the second embodiment will be described in detail below. The solvent contained in the raw material solution according to the second embodiment and the concentration of the solute in the raw material solution are the same as those in the first embodiment, so redundant description will not be repeated. The carboxylic acid having 1 to 4 carbon atoms contained in the solvent in the raw material solution according to the second embodiment can increase the solubility of the solute and improve the dissolution stability of the solute.

[0061] <Solute> The composite oxide contained in the solute dissolves in a solvent having the above-described composition, and can exist stably in the solvent without being precipitated or the like.

[0062] As described above, the composite oxide ｘ Ba ｙ Cu ｚ O １５－δ The compound is represented by the chemical formula: RE in the above chemical formula represents a rare earth element. In the above chemical formula, RE is at least one rare earth element selected from the group consisting of Y, Gd, La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu. RE represented by the above chemical formula may be both or either Y and Gd.

[0063] The above composite oxide is a so-called RE １ Ba ２ Cu ３ O ７ If RE ｘ Ba ｙ Cu ｚ O 15－δ In the chemical formula, x is 0.9 or more and 1.1 or less, y is 1.8 or more and 2.2 or less, and z is 2.7 or more and 3.3 or less. x may be 0.95 or more and 1.05 or less, y is 1.9 or more and 2.1 or less, and z is 2.85 or more and 3.15 or less. x may be 1, y may be 2, and z may be 3. δ may be more than 8 and 8.2 or less. δ may be more than 8 and 8.1 or less.

[0064] The above composite oxide is a so-called RE １ Ba ２ Cu ４ O ８ If RE ｘ Ba ｙ Cu ｚ O 15－δ In the chemical formula, x is 0.9 or more and 1.1 or less, y is 1.8 or more and 2.2 or less, and z is 3.7 or more and 4.3 or less. x may be 0.95 or more and 1.05 or less, y is 1.9 or more and 2.1 or less, and z is 3.85 or more and 4.15 or less. x may be 1, y may be 2, and z may be 4. δ may be more than 7 and 7.2 or less. δ may be more than 7 and 7.1 or less.

[0065] The above composite oxide is a so-called RE ２ Ba ４ Cu ７ O １５ If RE ｘ Ba ｙ Cu ｚ O 15－δ In the chemical formula, x is 1.9 or more and 2.1 or less, y is 3.8 or more and 4.2 or less, and z is 6.7 or more and 7.3 or less. The x may be 1.95 or more and 2.05 or less, the y may be 3.9 or more and 4.1 or less, and z may be 6.85 or more and 7.15 or less. The x may be 2, the y may be 4, and the z may be 7. The δ may be more than 0 and 0.2 or less. The δ may be more than 0 and 0.1 or less.

[0066] <Effects> When obtaining the raw material solution, the composite oxide may be added to the solvent in the form of powder or granules obtained by crushing a bulk mass and then dissolved therein. In this way, the raw material solution can be prepared as a raw material solution that can efficiently provide a high-quality oxide superconducting material.

[0067] [Third embodiment: method for producing an oxide superconducting material using a raw material solution containing a rare earth carboxylate, a barium carboxylate, and a copper carboxylate as solutes] As shown in FIG. 1 , the method for producing an oxide superconducting material according to the third embodiment is a method for producing an oxide superconducting material using the raw material solution according to the first embodiment.

[0068] The manufacturing method includes a step S110 of preparing a raw material solution, a step S120 of forming a coating film by applying the raw material solution onto a substrate, a step S130 of heating the coating film and thermally decomposing a solute-derived compound in the coating film to form a calcined film, and a step S140 of heating the calcined film to form an oxide superconducting material.

[0069] The solute-derived compound is a solute contained in the raw material solution, which contains a rare earth carboxylate salt, a barium carboxylate salt, and a copper carboxylate salt as solutes.

[0070] The method for producing an oxide superconducting material according to the third embodiment can obtain an oxide superconducting material under heat treatment conditions of low temperature and short time in the step of forming the oxide superconducting material. Therefore, the method for producing an oxide superconducting material can efficiently obtain an oxide superconducting material.

[0071] In particular, the method for producing an oxide superconducting material may further include a step S111 of filtering the raw material solution after the step S110 of preparing the raw material solution and before the step S120 of forming the coating film. In this case, by removing insoluble impurities in the raw material solution, an oxide superconducting material of higher quality can be obtained.

[0072] The raw material solution prepared in the method for producing an oxide superconducting material according to the third embodiment corresponds to the raw material solution according to the first embodiment. Therefore, the solute and solvent contained in the raw material solution used in the above production method, as well as the concentration of the solute in the raw material solution, are the same as those according to the first embodiment, and therefore redundant explanations will not be repeated. Below, each step included in this embodiment will be described in detail.

[0073] <Step S110 of Preparing a Raw Material Solution> The purpose of step S110 of preparing a raw material solution is to prepare a raw material solution that can efficiently produce an oxide superconducting material. Specifically, the raw material solution is prepared by dissolving solutes containing the above-mentioned rare earth carboxylate salt, barium carboxylate salt, and copper carboxylate salt in a solvent containing water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms at room temperature using a known dissolution method. The molar ratio of the salts of each carboxylic acid in the solute used to prepare the raw material solution and the volume ratio of each component in the solvent are adjusted to be as described in the first embodiment.

[0074] From the viewpoint of producing a high-quality oxide superconducting material, Cl (chlorine) may be added to the raw material solution as described in the first embodiment. In this case, the quality of the oxide superconducting material can be improved by increasing the superconducting properties such as the critical current density Jc and the critical current Ic. The raw material solution to which Cl is added is prepared, for example, by adding a Cl source such as ammonium chloride to the alcohol and then dissolving the dried material described below in the alcohol.

[0075] <Step S111 of filtering raw solution> The purpose of step S111 of filtering raw solution is to remove insoluble impurities from the raw solution and improve the quality of the oxide superconductor obtained from the raw solution. Specifically, step S111 of filtering raw solution may be a step in which the raw solution is filtered through a filter. The filter can be used without any particular limitation as long as it has chemical and mechanical durability during the filtration of the raw solution. The filter can be, for example, a polytetrafluoroethylene (PTFE) filter with a pore size of 0.2 μm.

[0076] <Step S120 of forming a coating film> The purpose of step S120 of forming a coating film is to form a coating film by applying the raw material solution prepared as described above, or the raw material solution prepared and filtered as described above, onto a substrate.

[0077] The substrate onto which the raw material solution is applied can be any substrate having heat resistance to the heat treatments (calcination, firing, annealing, etc.) described below and mechanical strength, without any particular limitations. The substrate may be a textured substrate comprising a metal substrate and an orientation layer provided on the metal substrate. Specific examples of the textured substrate include an IBAD (Ion Beam Assisted Deposition) substrate comprising an IBAD layer such as magnesium oxide on a metal substrate, and a clad substrate comprising a copper layer, a nickel layer, etc. laminated on a metal substrate. The metal constituting the metal substrate is, for example, stainless steel or Hastelloy (registered trademark).

[0078] The coating method for applying the raw material solution to the substrate is not particularly limited as long as the raw material solution can be uniformly applied. Examples of the coating method include die coating, spin coating, spray coating, and inkjet coating. The thickness of the coating film formed on the substrate may be 1 μm to 20 μm per coating, from the viewpoint of obtaining an oxide superconductor material with an appropriate thickness. Furthermore, the coating film may be formed by applying the raw material solution to the substrate and then drying the applied solution. The drying method for forming the coating film on the substrate is not particularly limited as long as the raw material solution can be uniformly dried. Examples of the drying method include heat drying, hot air drying, and infrared drying. The drying temperature may be 100°C to 250°C, or 150°C to 230°C. Note that if the next step, step S130 of forming a calcined film, is performed immediately after this step, a drying process may not be provided in this step if the coating film naturally dries due to the heating in step S130 of forming a calcined film.

[0079] <Step S130 of forming a calcined film> The purpose of step S130 of forming a calcined film is to form a calcined film from the coating film by heating and calcining the coating film formed on the substrate as described above.

[0080] The heating atmosphere for the coating film in step S130 for forming the calcined film may contain oxygen from the viewpoint of forming a uniform calcined film, and may further contain water vapor with a dew point of 10°C or higher, as necessary. When oxygen is contained, the oxygen pressure in the heating atmosphere is, for example, 10 kPa (approximately 0.1 atmospheres) or higher. The heating temperature for forming the calcined film may be 450°C or higher and 600°C or lower, or 480°C or higher and 550°C or lower.

[0081] The calcined film may have a single layer structure or a multilayer structure, i.e., the steps from step S120 of forming a coating film to step S130 of forming a calcined film may be repeated multiple times as necessary until the calcined film reaches a desired thickness, so that the calcined film may have a multilayer structure.

[0082] <Step S140 of Forming an Oxide Superconducting Material> The purpose of step S140 of forming an oxide superconducting material is to heat and fire the calcined film formed as described above to form an oxide superconducting material from the calcined film. This step produces a film-like oxide superconducting material (hereinafter also referred to as an "oxide superconducting film"). The thickness of the oxide superconducting film may be 0.1 μm or more and 4.0 μm or less. The heating atmosphere in which the calcined film is heated and fired is an oxygen-containing atmosphere. The oxygen partial pressure may be, for example, 1 Pa or more and 500 Pa or less. The heating temperature when the calcined film is heated and fired may be 700° C. or more and 780° C. or less, 740° C. or more and 780° C. or less, or 740° C. or more and 760° C. or less, for example, when the rare earth element contained in the oxide superconducting material to be obtained by firing is Y.

[0083] The heating time when the calcined film is heated and fired may be from 1 minute to 90 minutes, or from 1 minute to 60 minutes. Here, the relationship between the heating temperature and the heating time when the calcined film is heated and fired may satisfy the following relationship: When the heating temperature is from 740°C to 760°C, the heating time may be from 1 minute to 90 minutes, and when the heating temperature is from 760°C to 780°C, the heating time may be from 1 minute to 60 minutes.

[0084] In conventional methods for producing oxide superconductors using the MOD method, the heating temperature when the calcined film is heated and fired generally exceeds 760°C. The heating time when the calcined film is heated and fired is, for example, 1 minute to 120 minutes when the temperature is around 760°C, and 1 minute to 90 minutes when the temperature is 770°C to 800°C. Therefore, the relationship between the heating temperature and heating time when the calcined film is heated and fired in step S140 to form the oxide superconductor can be evaluated as being lower and shorter than those in conventional methods for producing oxide superconductors using the MOD method. Therefore, the above production method makes it possible to efficiently obtain oxide superconductors.

[0085] The heating temperature and heating time required in this step vary depending on the type of rare earth element contained in the oxide superconducting material, and therefore the relationship between the heating temperature and heating time can be adjusted appropriately depending on the type of rare earth element contained in the oxide superconducting material.

[0086] In order to form a high-quality oxide superconducting film, the step S140 of forming the oxide superconducting material may include an annealing step of heat-treating the oxide superconducting film obtained by heating and firing the calcined film. The annealing step makes it possible to control the concentration of oxygen contained in the oxide superconducting film. The heating atmosphere in the annealing step is an atmosphere containing oxygen. The oxygen partial pressure is, for example, 1×10 4 The heating temperature in the annealing step may be 150°C or higher and 600°C or lower, or 200°C or higher and 550°C or lower.

[0087] [Fourth embodiment: Method for producing an oxide superconducting material using a raw material solution containing a complex oxide as a solute] As shown in FIG. 2 , the method for producing an oxide superconducting material according to the fourth embodiment is a method for producing an oxide superconducting material using the raw material solution according to the second embodiment.

[0088] The manufacturing method includes a step S210 of preparing a raw material solution, a step S220 of forming a coating film by applying the raw material solution onto a substrate, a step S230 of heating the coating film and thermally decomposing a solute-derived compound in the coating film to form a calcined film, and a step S240 of heating the calcined film to form an oxide superconducting material.

[0089] The solute-derived compound is a solute contained in the raw material solution, which contains a complex oxide as a solute.

[0090] The step S210 of preparing a raw material solution includes the steps of obtaining a precursor solution by dissolving the solute in the carboxylic acid, obtaining a dried product by drying the precursor solution, and obtaining the raw material solution by dissolving the dried product in a liquid containing the alcohol.

[0091] The method for producing an oxide superconductor according to the fourth embodiment can produce an oxide superconductor under heat treatment conditions of low temperature and short time in the step of forming the oxide superconductor. In addition, the method for producing an oxide superconductor can produce an oxide superconductor with a more uniform atomic ratio because the solute of the raw material solution is an oxide superconductor. Therefore, the method for producing an oxide superconductor can efficiently produce a high-quality oxide superconductor.

[0092] In particular, the method for producing an oxide superconducting material may further include a step S211 of filtering the raw material solution after the step S210 of preparing the raw material solution and before the step S220 of forming the coating film. In this case, by removing insoluble impurities in the raw material solution, an oxide superconducting material of higher quality can be obtained.

[0093] The method for producing an oxide superconducting material according to the fourth embodiment is the same as the method for producing an oxide superconducting material according to the third embodiment, except for the characteristics of the solute contained in the raw material solution prepared in the fourth embodiment and the details of step S210 for preparing the raw material solution. Furthermore, the raw material solution prepared in the method for producing an oxide superconducting material according to the fourth embodiment is the raw material solution according to the second embodiment. Therefore, the steps other than step S210 for preparing the raw material solution included in the above-mentioned production method, the solute and solvent contained in the raw material solution used in the above-mentioned production method, and the concentration of the solute in the raw material solution are the same as those in the third or second embodiment, and therefore redundant description will not be repeated. Below, each step included in step S210 for preparing the raw material solution will be described.

[0094] <Step S210 of Preparing a Raw Material Solution> Regarding step S210 of preparing a raw material solution, first, the step of obtaining a precursor solution by dissolving the solute in the carboxylic acid is a step of dissolving a solute containing the complex oxide described above in a carboxylic acid having 1 to 4 carbon atoms, which is one of the solvents contained in the raw material solution. This step obtains a precursor solution in which at least one selected from the group consisting of rare earth carboxylate salts, barium carboxylate salts, copper carboxylate salts, and complex metal carboxylate salts containing two or more metals is dissolved in the carboxylic acid. Examples of complex metal carboxylate salts containing two or more metals include rare earth barium carboxylate salts, rare earth copper carboxylate salts, barium copper carboxylate salts, and rare earth barium copper carboxylate salts. In this step, the precursor solution may be prepared, for example, by mixing the solute in a solvent heated to room temperature or higher and 80°C or lower using a known mixing method.

[0095] The specific aspects of the carboxylic acid are the same as those described in the section (Carboxylic acid having 1 to 4 carbon atoms) in the first embodiment, and therefore redundant explanations will not be repeated. In particular, the carboxylic acid used to prepare the precursor solution may be propionic acid.

[0096] Next, the step of obtaining a dried body by drying the precursor solution involves heating the precursor solution by an appropriate means to remove the carboxylic acid and dry the solution to obtain a dried body. This step provides a dried body from which the carboxylic acid has been removed to a concentration of 20% by volume or less, 10% by volume or less, 5% by volume or less, or 1% by volume or less in the solvent of the raw material solution. A known heating device can be used as the heating means for heating the precursor solution. For example, a commercially available hot plate can be used as the heating means. The dried body can be obtained by heating the precursor solution on the hot plate for about four hours while changing the temperature, for example, from 90°C to 180°C and then 90°C. Note that the above temperatures are the set temperatures of the hot plate. The actual temperature of the precursor solution corresponds to approximately 130°C when the hot plate is set to 180°C, and to approximately 70°C when the hot plate is set to 90°C. The heating time required for drying varies depending on the amount of solution. Therefore, the heating time is not limited to approximately four hours and can be changed as appropriate depending on the amount of solution. Depending on the amount of solution, a dried product can be obtained even if the solution is heated for, for example, one hour or more.

[0097] Furthermore, the step of obtaining the raw material solution by dissolving the dried material in a liquid containing the alcohol is a step of dissolving the dried material in an alcohol having a carbon number of 1 to 4, which is one of the solvents contained in the raw material solution. This step obtains a raw material solution in which the dried material is dissolved in the alcohol. In this step, the raw material solution is prepared by dissolving the dried material in the alcohol at room temperature using a known dissolution method. The specific aspects of the alcohol are the same as those described in the section (alcohol having a carbon number of 1 to 4) in the first embodiment, so redundant explanations will not be repeated. As described above, the raw material solution is prepared in step S210 of preparing a raw material solution.

[0098] From the viewpoint of producing a high-quality oxide superconducting material, Cl (chlorine) may be added to the raw material solution as described in the first embodiment. In this case, the quality can be improved by increasing the superconducting properties of the oxide superconducting material, such as the critical current density Jc and the critical current Ic. A method for preparing the raw material solution to which Cl is added is, for example, a method in which a Cl source such as ammonium chloride is added to the alcohol and the dried body is then dissolved in the alcohol.

[0099] [Fifth Embodiment: Use of Raw Material Solution] The oxide superconducting material produced using the raw material solution according to at least one of the first and second embodiments described above may be used to produce a superconducting wire. The superconducting wire may be a superconducting coil, a superconducting cable conductor, a superconducting junction, a nuclear magnetic resonance apparatus, a nuclear magnetic resonance imaging apparatus, or a superconducting wire included in a nuclear fusion reactor. In this case, a superconducting wire applicable to each application can be efficiently produced.

[0100] [Sixth embodiment: Superconducting wire] A superconducting wire according to a sixth embodiment includes the oxide superconducting material produced using the raw material solution. The oxide superconducting material may be produced from the raw material solution using the method for producing the oxide superconducting material. This allows the oxide superconducting material to be produced efficiently from the raw material solution. The oxide superconducting material is a material containing an RE ｘ Ba ｙ Cu ｚ O １５－δ Specifically, the oxide superconducting material is represented by the chemical formula: RE １ Ba ２ Cu ３ O ７、 RE １ Ba ２ Cu ４ O ８、 or RE ２ Ba ４ Cu ７ O １５The superconducting wire may have a superconducting layer formed by stacking oxide superconducting films manufactured using the method for manufacturing an oxide superconducting material. Such a superconducting wire may be applied, for example, as a superconducting wire contained in a superconducting coil, a superconducting wire contained in a superconducting cable conductor, a superconducting wire contained in a superconducting junction, a superconducting wire contained in a nuclear magnetic resonance apparatus, a superconducting wire contained in a nuclear magnetic resonance imaging apparatus, and a superconducting wire contained in a nuclear fusion reactor. FIG. 3 shows an example of a superconducting wire 1 according to one aspect of the present disclosure.

[0101] [Seventh Embodiment: Apparatus] The apparatus according to the seventh embodiment includes the superconducting wire described above. The apparatus may include the superconducting wire according to the sixth embodiment, which is manufactured from the raw material solution using the method for manufacturing an oxide superconducting material described above. The superconducting wire according to the sixth embodiment includes the oxide superconducting material that can be efficiently manufactured from the raw material solution. By using such a superconducting wire, the apparatus can be efficiently manufactured. The apparatus is, for example, an apparatus including a superconducting coil, an apparatus including a superconducting cable, an apparatus including a superconducting junction, a nuclear magnetic resonance apparatus, a nuclear magnetic resonance imaging apparatus, or a nuclear fusion reactor. FIG. 4 shows a nuclear magnetic resonance apparatus 10 as an example of an apparatus according to one aspect of the present disclosure.

[0102] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited thereto. In the first, second, and third examples, superconducting wires (oxide superconducting materials) each having an IBAD substrate and an oxide superconducting film were manufactured from each sample.

[0103] [First Example] [Preparation of Raw Material Solution and Production of Oxide Superconducting Material] <Step of Preparing Raw Material Solution> (Solute) To prepare the raw material solutions of Samples 11 to 12 and Samples 101 to 103, Gd １ Ba ２ Cu ３ O ７ or Y １ Ba ２ Cu ３ O ７This was prepared by purchasing a composite oxide represented by the following chemical formula from the market. This was used as the solute contained in the raw material solutions of Samples 11 to 12 and Samples 101 to 103.

[0104] (Solvents) To prepare the raw solution of Samples 11 to 12 and Samples 101 to 103, water, methanol, 1-butanol, propionic acid, acetic acid, and pyridine were purchased from the market. These were then mixed together in the volume ratios shown in Table 1 to form the solvents contained in the raw solution of Samples 11 to 12 and Samples 101 to 103. The volume ratios (%) of the solvents shown in Table 1 and Tables 2 to 7 described below are the percentages that each solvent component accounts for when the total volume of the solvent is 100% by volume.

[0105] (Preparation of Raw Material Solutions) Raw material solutions for Samples 11 to 12 were prepared according to the process for preparing the raw material solutions described above. Specifically, a precursor solution containing a solute dissolved in propionic acid was heated on a hot plate at 90°C, 180°C, and 90°C in that order for approximately four hours to obtain a dried product. The dried product was then dissolved in a solvent containing water, methanol, 1-butanol, and acetic acid to prepare a raw material solution. Raw material solutions for Samples 101 to 103 were prepared in the same manner as Samples 11 to 12, except that the dried product was dissolved in a solution containing water, methanol, 1-butanol, propionic acid, and pyridine. The solute concentrations in the raw material solutions for Samples 11 to 12 and Samples 101 to 103 were each 1.0 mol / L.

[0106] <Step of filtering raw material solution> Filtration was carried out on the raw material solutions of Samples 11 to 12 and Samples 101 to 103. A PTFE (polytetrafluoroethylene) filter with a pore size of 0.2 μm (50JP020AN manufactured by Advantec Co., Ltd. or an equivalent product) was used as the filtration filter.

[0107] <Step of forming a coated film and step of forming a calcined film> The raw material solutions of Samples 11 to 12 and Samples 101 to 103 were die-coated to a thickness of 5 μm on an IBAD substrate measuring 5000 mm in length, 30 mm in width, and 120 μm in thickness, and then heat-treated (calcined) at 500°C in an oxygen-containing atmosphere with a dew point of 19°C. The oxygen pressure in the atmosphere was 100 kPa (1 atmosphere). This coating and heat-treatment operation was performed multiple times.

[0108] <Step of forming oxide superconducting material> The calcined films obtained from the raw material solutions of Samples 11 to 12 and Samples 101 to 103 were subjected to a heat treatment (firing) in an argon / oxygen mixed gas atmosphere at the heating temperature and for the heating time shown in Table 1. The oxygen concentration in the atmosphere was 100 ppm, CO ２ The concentration was 1 ppm or less. The oxygen pressure in the atmosphere was 10 Pa. Then, oxygen annealing was performed at 500°C in an atmosphere with an oxygen concentration of 100%, and the amount of oxygen in the fired film was controlled to obtain oxide superconductors (oxide superconducting films) of Samples 11 to 12 and Samples 101 to 103. Table 1 shows the thicknesses (film thickness, unit μm) of the oxide superconductors of Samples 11 to 12 and Samples 101 to 103.

[0109] [Evaluation] <Critical current density Jc of oxide superconducting material> The critical current Ic (A) per 1 cm width of the oxide superconducting materials of Samples 11 to 12 and Samples 101 to 103 was measured by passing current through them by the four-terminal method at 77.3 K (Kelvin), and the critical current density Jc (MA / cm) was calculated by dividing the critical current Ic (A) per 1 cm width of the oxide superconducting materials by the width and the film thickness of the oxide superconducting material (oxide superconducting film). ２ The results are shown in Table 1.

[0110]

[0111] [Discussion] Table 1 shows that the oxide superconducting materials obtained from the raw solution of Samples 11 and 12 can be obtained under heat treatment conditions at a lower temperature and for a shorter time to achieve the same level of performance as the oxide superconducting material obtained from the raw solution of Sample 101. The above suggests that the raw solution of Samples 11 and 12 can be used to efficiently produce oxide superconducting materials. Sample 101 contained a large amount of pyridine, a basic organic solvent, and required a high heating temperature and a long heating time. It is believed that the solvent mixing ratio was inappropriate for Sample 102, which resulted in a low Jc. It is believed that Sample 103 contained a large amount of propionic acid and lacked a basic organic solvent to neutralize it, which resulted in a low Jc.

[0112] Second Example Preparation of Raw Material Solutions and Production of Oxide Superconducting Materials Raw material solutions for Samples 21 to 29, Sample 2A, and Samples 201 to 203 were prepared, and oxide superconducting materials for Samples 21 to 29, Sample 2A, and Samples 201 to 203 were produced in the same manner as in the first example, except that the solute and solvent contained in the raw material solutions were prepared as follows. Furthermore, the critical current densities Jc of the oxide superconducting materials for Samples 21 to 29, Sample 2A, and Samples 201 to 203 were measured in the same manner as in the first example. The results are shown in Tables 2 and 3. Tables 2 and 3 also show the thicknesses (film thickness, unit: μm) of the oxide superconducting materials for Samples 21 to 29, Sample 2A, and Samples 201 to 203.

[0113] (Solute) That is, Gd propionate, Ba propionate, and Cu propionate were purchased from the market and prepared for the preparation of raw material solutions of Samples 21 to 29, Sample 2A, and Samples 201 to 203. Next, Gd propionate, Ba propionate, and Cu propionate were mixed in a molar ratio of 1:2:3 as shown in Tables 2 and 3, respectively, to form the solutes contained in the raw material solutions of Samples 21 to 29, Sample 2A, and Samples 201 to 203.

[0114] (Solvent) Water, methanol, 1-butanol, propionic acid, acetic acid, and pyridine were purchased commercially and prepared for preparing the raw material solutions of Samples 21 to 29, Sample 2A, and Samples 201 to 203. These were then mixed in the volume ratios shown in Tables 2 and 3, respectively, to form the solvents contained in the raw material solutions of Samples 21 to 29, Sample 2A, and Samples 201 to 203.

[0115]

[0116]

[0117] [Discussion] Tables 2 and 3 show that the oxide superconducting materials obtained from the raw solution of Samples 21 to 29 and Sample 2A can be obtained under heat treatment conditions at a lower temperature and for a shorter time to achieve the same level of performance as the oxide superconducting material obtained from the raw solution of Sample 201. The above suggests that the raw solutions of Samples 21 to 29 and Sample 2A can be used to efficiently produce oxide superconducting materials. Sample 201 contained a large amount of the basic organic solvent pyridine, which required a high heating temperature and a long heating time. It is believed that the solvent mixing ratio was inappropriate for Sample 202, resulting in a low Jc. It is believed that the Jc of Sample 203 was low because it contained a large amount of propionic acid and lacked a basic organic solvent to neutralize it.

[0118] [Example 3] [Preparation of raw material solution and production of oxide superconducting material] Raw material solutions for Samples 31 to 39 were prepared and oxide superconducting materials for Samples 31 to 39 were produced in the same manner as in Example 1, except that the solute and solvent contained in the raw material solution were prepared as follows. Furthermore, the critical current density Jc of the oxide superconducting materials for Samples 31 to 39 was measured in the same manner as in Example 1. The results are shown in Tables 4 and 5. Tables 4 and 5 also show the thicknesses (film thickness, unit: μm) of the oxide superconducting materials for Samples 31 to 39.

[0119] (Solutes) That is, to prepare the raw material solutions of Samples 31 to 39, Y propionic acid, Y acetate, Gd acetate, Ba propionate, Ba acetate, Cu propionate, and Cu acetate were purchased from the market and prepared. These were then blended in the molar ratios shown in Tables 4 and 5, respectively, to form the solutes contained in the raw material solutions of Samples 31 to 39.

[0120] (Solvent) Water, methanol, 1-butanol, propionic acid, and acetic acid were purchased from the market and prepared to prepare the raw solution of Samples 31 to 39. Then, as shown in Tables 4 and 5, these were blended to form a solvent contained in the raw solution of Samples 31 to 39, with 10% by volume of water, 44% by volume of methanol, 44% by volume of 1-butanol, 1% by volume of propionic acid, and 1% by volume of acetic acid.

[0121]

[0122]

[0123] [Discussion] Tables 4 and 5 show that the oxide superconducting materials obtained from the raw material solutions of Samples 31 to 39 can be obtained under heat treatment conditions of lower temperature and shorter time to achieve the same level of performance as the oxide superconducting material obtained from the raw material solution of Sample 201 in Example 2. This suggests that the raw material solutions of Samples 31 to 39 can be used to efficiently produce oxide superconducting materials.

[0124] [Example 4] [Preparation of Raw Material Solutions and Production of Oxide Superconducting Materials] Raw material solutions for Samples 41 to 49, Sample 4A, and Sample 401 were prepared, and oxide superconducting materials for Samples 41 to 49, Sample 4A, and Sample 401 were produced in the same manner as in Example 1, except that the solute and solvent contained in the raw material solutions were prepared as follows. Furthermore, the critical current densities Jc of the oxide superconducting materials for Samples 41 to 49, Sample 4A, and Sample 401 were measured in the same manner as in Example 1. The results are shown in Tables 6 and 7. Tables 6 and 7 also show the thicknesses (film thickness, unit: μm) of the oxide superconducting materials for Samples 41 to 49, Sample 4A, and Sample 401.

[0125] (Solute) For the preparation of the raw material solutions of Samples 41 to 49, Sample 4A, and Sample 401, Gd １ Ba ２ Cu ３ O ７ This was used as the solute contained in the raw material solutions of Samples 41 to 49, Sample 4A, and Sample 401.

[0126] Water, methanol, 1-butanol, propionic acid, acetic acid, and pyridine were purchased from the market and prepared to prepare the raw material solutions of Samples 41 to 49, Sample 4A, and Sample 401. These were then mixed in the volume ratios shown in Tables 6 and 7, respectively, to form the solvents contained in the raw material solutions of Samples 41 to 49, Sample 4A, and Sample 401.

[0127]

[0128]

[0129] [Discussion] Tables 6 and 7 show that the oxide superconducting materials obtained from the raw material solutions of Samples 41 to 49 and Sample 4A can be obtained under heat treatment conditions of lower temperature and shorter time to achieve the same level of performance as the oxide superconducting material obtained from the raw material solution of Sample 401. This suggests that the raw material solutions of Samples 41 to 49 and Sample 4A can be used to efficiently produce oxide superconducting materials.

[0130] Although the embodiments and examples according to the present disclosure have been described above, it is also intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined.

[0131] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0132] 1 Superconducting wire, 10 Apparatus (nuclear magnetic resonance apparatus), S110, S210 Step of preparing raw material solution, S111, S211 Step of filtering raw material solution, S120, S220 Step of forming coating film, S130, S230 Step of forming calcined film, S140, S240 Step of forming oxide superconducting material.

Claims

1. A raw material solution used in the production of oxide superconducting material using a coating pyrolysis method, comprising, as solutes, a rare earth carboxylate salt, a barium carboxylate salt, and a copper carboxylate salt; and, as solvents, water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms, wherein the solvent contains 0.01 to 35% by volume of water, 45 to 99.99% by volume of alcohol, and 20% by volume or less of carboxylic acid.

2. The raw material solution according to claim 1, wherein at least one of the rare earth carboxylate salt, the barium carboxylate salt, and the copper carboxylate salt is a salt of a monocarboxylic acid having 1 to 4 carbon atoms.

3. A raw material solution used in the production of oxide superconducting material using a coating pyrolysis method, comprising a composite oxide as a solute, and water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms as a solvent, wherein the water is contained in an amount of 0.01% by volume to 35% by volume, the alcohol is contained in an amount of 45% by volume to 99.99% by volume, and the carboxylic acid is contained in an amount of 20% by volume or less, and the composite oxide is a compound having a structure selected from the group consisting of RE, ｘ Ba ｙ Cu ｚ O １５－δ wherein x is 0.7 or more and 2.1 or less, y is 1.8 or more and 4.2 or less, z is 2.7 or more and 7.3 or less, and δ is 0 or more and 8.5 or less.

4. The raw material solution according to any one of claims 1 to 3, wherein the solvent does not contain a basic organic solvent.

5. A raw material solution according to any one of claims 1 to 4, wherein the solvent contains a monocarboxylic acid having 2 to 3 carbon atoms as the carboxylic acid.

6. The raw material solution according to any one of claims 1 to 5, wherein the solvent contains propionic acid and acetic acid as the carboxylic acid.

7. The raw material solution according to any one of claims 1 to 6, wherein the alcohol is two or more types.

8. The source solution of claim 7, wherein each of the alcohols has an equal volume.

9. A raw material solution according to any one of claims 1 to 8, wherein the alcohol includes an alcohol having 1 to 2 carbon atoms and an alcohol having 3 to 4 carbon atoms.

10. The raw material solution according to claim 9, wherein the volume ratio of the alcohol having 1 to 2 carbon atoms to the alcohol having 3 to 4 carbon atoms is within the range of 5:1 to 1:

5.

11. A method for producing an oxide superconducting material, comprising: preparing a raw material solution; applying the raw material solution onto a substrate to form a coating film; heating the coating film to thermally decompose a solute-derived compound in the coating film to form a calcined film; and heating the calcined film to form an oxide superconducting material, wherein the solute-derived compound is a solute contained in the raw material solution, and the raw material solution contains, as the solutes, a rare earth carboxylate salt, a barium carboxylate salt, and a copper carboxylate salt, and contains, as a solvent, water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms, and wherein, in the solvent, the water is contained in an amount of 0.01% by volume to 35% by volume, the alcohol is contained in an amount of 45% by volume to 99.99% by volume, and the carboxylic acid is contained in an amount of 20% by volume or less.

12. A method for producing a superconducting oxide material, comprising: preparing a raw material solution; applying the raw material solution onto a substrate to form a coating; heating the coating to thermally decompose a solute-derived compound in the coating to form a calcined film; and heating the calcined film to form an oxide superconducting material, wherein the solute-derived compound is a solute contained in the raw material solution, and the raw material solution contains a complex oxide as the solute, and a solvent comprising water, an alcohol having 1 to 4 carbon atoms, and a carboxylic acid having 1 to 4 carbon atoms, wherein the solvent contains 0.01% by volume or more and 35% by volume or less, 45% by volume or more and 99.99% by volume or less of the alcohol, and 20% by volume or less of the carboxylic acid, and the complex oxide is a compound selected from the group consisting of RE ｘ Ba ｙ Cu ｚ O １５－δ wherein x is equal to or greater than 0.7 and equal to or less than 2.1, y is equal to or greater than 1.8 and equal to or less than 4.2, z is equal to or greater than 2.7 and equal to or less than 7.3, and δ is equal to or greater than 0 and equal to or less than 8.5, and the step of preparing the raw material solution includes the steps of: dissolving the solute in the carboxylic acid to obtain a precursor solution; drying the precursor solution to obtain a dried product; and dissolving the dried product in a liquid containing the alcohol to obtain the raw material solution.

13. A method for producing an oxide superconducting material according to claim 11 or 12, further comprising the step of filtering the raw material solution after the step of preparing the raw material solution and before the step of forming the coating film.

14. The raw material solution according to any one of claims 1 to 10, wherein the oxide superconducting material is used for producing a superconducting wire, and the superconducting wire is a superconducting coil, a superconducting cable conductor, a superconducting junction, a nuclear magnetic resonance apparatus, a nuclear magnetic resonance imaging apparatus, or a superconducting wire contained in a nuclear fusion reactor.

15. A superconducting wire comprising the oxide superconducting material produced using the raw material solution according to any one of claims 1 to 10.

16. A device comprising the superconducting wire of claim 15.

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