JPH03102715A - Superconductive ceramics wire material and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve flexibility, superconductivity and mechanical strength by coating the periphery of an oxide layer, including titanium or magnesium, formed on the periphery of heat-resistant ceramic fiber, with oxide superconductive ceramics. CONSTITUTION:A heat-resistant ceramic fiber of flexibility used as core material has the surface provided with an oxide layer including mainly titanium or magnesium not to react on superconductive ceramics and coated with oxide superconductive ceramics. It is thus possible to obtain a superconductive ceramics wire material that the crystal of superconductive ceramics is sintered finely and densely, the critical temperature and critical current density are high and still the flexibility is excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a superconducting ceramic wire and a method for manufacturing the same, and particularly the present invention relates to a superconducting ceramic wire with excellent flexibility and a method for manufacturing the same.

(Prior Art) In recent years, superconducting ceramics that can be used even in the liquid nitrogen temperature range have been discovered, and this has had a great impact on industry. As a typical example, Y-Ba-Cu-0 based oxide superconducting ceramics are well known. Also,
Recently, Bi-Sr-Ca-Cu-0 system or TQ-Ba-C-Cu-0 system oxide superconducting ceramics have been reported as new types of superconducting ceramics that do not contain rare earth elements. Conductive ceramics are characterized by excellent stability against moisture and carbon dioxide in the atmosphere, as well as stable superconducting properties due to a constant oxygen content.

However, in order to put these superconducting ceramics into practical use, it is essential to convert them into wire rods, and an important technical issue is how to sinter these hard and brittle ceramics into wire rods. Ta.

The method for manufacturing wire rods made of superconducting ceramics is as follows:
For example, 1) Ceramics magazine VOL22 (1987) N
No. 6, page 526, describes a method for producing a wire rod, in which a silver pipe is filled with ceramic powder, the wire is drawn, wound into a coil shape, and then heat-treated in an oxygen atmosphere. 2) According to an announcement by Argonne National Laboratory, a method for manufacturing a wire made of superconducting ceramics involves mixing Y-Ba-Cu-0 powder with a polymer, forming it into a wire, and then burning it to make a flexible wire. is proposed. Furthermore, 3) Japanese Journal of App
Lied Physics, Vo1.26 (1987)
Y, Ba on page 1211 of Supplement 26-3
, a solution consisting of Cu nitrate and Y. 0. , BaCOg
A method for manufacturing a wire rod is described in which CuO powder is mixed, formed into a wire shape, and then fired.

However, in method 1), since the ceramic powder is heat-treated in a metal pipe, it is difficult to obtain an m-dense sintered body, and it is difficult to obtain sufficient superconducting contact between the particles. Another drawback is that it is difficult to precisely control oxygen, which has a large effect on properties.

With method 2), it is difficult to maintain the shape of the polymer from the time it burns until sintering begins, and if you try to sinter it densely, the crystal grains will grow and the mechanical properties will deteriorate. The problem is that the superconducting properties tend to deteriorate significantly due to decomposition or decomposition.

Furthermore, the wire rod obtained by method 3) has the problem that when it is attempted to be sintered densely, crystal grains grow, resulting in poor mechanical properties and a tendency to deteriorate flexibility.

(Problem to be solved by the invention) As mentioned above, in the methods known so far, the crystals of superconducting ceramics are finely and densely sintered, and the critical temperature
It has been difficult to obtain a superconducting ceramic wire that has a high critical current density and excellent flexibility.

As a result of various studies, the inventors of the present invention used a flexible heat-resistant ceramic fiber as a core material, and formed an oxide layer containing mainly titanium or magnesium on the surface of the core material, which does not react with superconducting ceramics. , then by coating with oxide superconducting ceramics,
The inventors have discovered that the above-mentioned problems can be solved, and have completed the present invention.

By the way, Journal of Crystal
Growth 91 (+988) 346-351,
A technique has been described in which a 2-ethylhexanate solution of Y, Ba, and Cu is coated on a single crystal substrate of strontium titanate, zirconia, and magnesia, and then heat-treated to form a superconducting ceramic thin film. this is,
A technique for forming superconducting ceramics on a single crystal substrate, as intended by the present invention, in which oxides such as strontium titanate and magnesia are used to prevent reactions between the core material and the superconducting ceramics. It wasn't meant to be used.

Furthermore, Japanese Patent Application Laid-open No. 64-21824 discloses that yttrium oxide stabilized zirconia or the like is used as a core material for ceramic fibers, etc., to suppress the reaction with oxide superconducting ceramics, if necessary. A technology has been described in which a superconducting ceramic wire is manufactured by coating the surface of a metal compound with an oxide superconducting composition and then thermally decomposing it. This invention uses zirconia ceramics, which is different from the present invention which uses oxides containing titanium or magnesium, and furthermore, the oxides containing titanium or magnesium are more concentrated than the stabilized zirconia ceramics. It has low reactivity with oxide superconducting ceramics under high temperature conditions and is more suitable as a buffer layer.

Therefore, the novelty and inventive step of the present invention are not impaired in any way by the above technique.

(Means for Solving the Problems) The present invention provides a heat-resistant ceramic fiber, an oxide layer formed on the surface of the ceramic fiber and mainly containing titanium or magnesium, and an oxide coating around the oxide layer. An oxide layer containing mainly titanium or magnesium is formed on the surface of a superconducting ceramic wire made of superconducting ceramics and a heat-resistant ceramic fiber, and on top of the oxide layer, an organic metal compound having an oxide superconducting composition is formed. A method for producing superconducting ceramics, which is characterized by coating the ceramics with a solution and then firing them.

(for production) This will be explained in detail below.

The superconducting ceramic wire of the present invention consists of a heat-resistant ceramic fiber, an oxide layer formed around it and mainly containing titanium or magnesium, and an oxide superconducting ceramic layer formed around the oxide layer. It is characterized by

The reason for this structure is that by forming an oxide superconducting ceramic layer around the heat-resistant ceramic fiber, the mechanical brittleness peculiar to ceramics can be improved, and furthermore, the oxide superconducting ceramic layer mainly containing titanium or magnesium can be improved. By using the layer as a buffer layer, it is possible to suppress the interaction between the heat-resistant ceramic fiber and the oxide superconducting ceramic during firing, and prevent the core material from deteriorating and the superconducting properties from deteriorating. Furthermore, ceramic fibers having superior strength and heat resistance can be used as the core material compared to fibers made of oxides mainly containing titanium or magnesium.

Among oxides, oxides containing titanium or magnesium are particularly difficult to react with oxide superconducting ceramics.
Shows a suitable effect for preventing mutual reactions.

The oxide layer mainly containing titanium or magnesium is preferably made of at least one selected from titanium oxide, strontium titanate, and magnesium oxide.

The oxide layer preferably has a thickness of 2 μm or less. The reason for this is that if the thickness of the oxide layer exceeds 2 μm, the flexibility of the superconducting ceramic fiber will decrease.

The present invention will be explained in detail below.

The heat-resistant ceramic fiber used in the present invention is preferably a long fiber with a diameter of 40 μm or less, particularly preferably 20 μm or less. The reason is that heat-resistant ceramic fibers with a diameter larger than 40 μm lack flexibility, making it difficult to obtain a superconducting ceramic wire with excellent flexibility, which is the objective of the present invention. .

The heat resistant ceramic fiber has a heat resistance temperature of 750°C.
It is preferable that it is above.

The heat-resistant temperature is the temperature at which the heat-resistant ceramic fiber starts to melt. The reason why the heat-resistant ceramic fiber preferably has a heat resistance temperature of 750° C. or higher is that the firing temperature of the oxide superconducting ceramic is usually 750° C. or higher, and unless it can withstand this firing temperature, the initial fiber shape will be maintained. This is because it is difficult to obtain the superconducting ceramic wire that is the object of the present invention.

The heat-resistant ceramic fibers include alumina, silicon carbide, quartz, mullite, zirconia, boron, Si-
It is preferable to use any one type selected from Ti-C-0 type fibers.

The oxide superconducting ceramics used in the present invention are Y
The material is preferably at least one selected from the group consisting of Bi-based, Bi-based, and Tl-based.

The Y-based oxide superconducting ceramic is composed of at least a rare earth element, an alkaline earth element, copper, and oxygen, and includes, for example, YBa, Cu, Os, s+8, and T.
mBa, Cu*. Og. 6+X, (Lal-x Bax
) scuOt-y can be mentioned as a specific chemical formula, and in particular, oxide superconducting ceramics represented by the general formula RA, Cu, Og, s+x (R: rare earth element, A: alkaline earth gold Ji4) is suitable because it exhibits a high superconducting critical temperature of 90K class.

Further, the Bi-based oxide superconducting ceramic is composed of at least an element selected from the group consisting of bismuth, bismuth and aluminum, bismuth and lead, bismuth and potassium, bismuth and yttrium, an alkaline earth metal, copper, and oxygen. Its specific chemical composition is, for example, BiSrCaCu, Ox, B
i, Sr, Cat-x Y, Cu, Oy%BisxPb
xSr,Ca,Cu,O,,Bt + -xA Q,S
rCaCu, o,, BISr*73Ca27s Kz
Examples include is cu, of, Bi, SrCu, 07+y.

Furthermore, the Tl-based oxide superconducting ceramic is composed of at least thallium, an element selected from the group consisting of thallium and lead, an alkaline earth metal, copper, and oxygen, and its specific chemical composition is as follows: is TQ,
Ba, Ca, Cu, O,, T Q o. , pb. ，
5Sr, Ca, Cu. 0. etc. can be mentioned.

The superconducting ceramic wire of the present invention has a diameter of 80 μm.
The thickness is preferably equal to or less than 40 μm, particularly preferably equal to or less than 40 μm. The reason for this is that superconducting ceramic wires with a diameter exceeding 80 μm have significantly insufficient flexibility.

In addition, the superconducting ceramic wire obtained by the present invention has the following properties in order to stabilize its superconducting properties and improve its mechanical properties:
For example, various methods can be applied, such as placing it in a metal pipe made of silver or the like, coating the surface with metal by vacuum evaporation, sputtering, ion plating, etc., or coating it with non-porous plastic.

Next, a method for manufacturing a superconducting ceramic wire according to the present invention will be explained.

The superconducting ceramic wire of the present invention is produced by forming an oxide layer mainly composed of titanium or magnesium on the surface of a heat-resistant ceramic fiber, and then coating it with a solution composed of an organometallic compound having a superconducting oxide composition. Manufactured by firing.

The heat-resistant ceramic fiber used in the present invention has excellent mechanical strength and flexibility even at or above the firing temperature of oxide superconducting ceramics. The shape, mechanical properties, and flexibility of the heat-resistant ceramic fiber on which the oxide layer, which is the core material, is formed can be introduced into the superconducting ceramic wire, and the firing of the oxide superconducting ceramic can be applied to the superconducting ceramic wire. Since it can be carried out in the form of a film, the compatibility between the heat-resistant ceramic fiber on which the oxide layer, which is the core material, is formed and the oxide superconducting ceramic is good, and the mechanical strength is also high. Furthermore, since the organometallic compound solution having a superconducting oxide composition is fired, the fine crystals are densely and strongly sintered, and the critical temperature (Tc) and critical current density (Jc
) can produce homogeneous superconducting ceramic wires with excellent superconducting properties.

Furthermore, in order to prevent a reaction between the oxide superconducting ceramic and the core material during firing, an oxide layer mainly made of titanium or magnesium is provided on the surface of the core material.
Deterioration of superconducting properties and deterioration of the core material can be prevented.

In the present invention, the oxide layer is preferably formed by applying a solution containing a compound of elements constituting the oxide and then firing the solution.

Suitable examples of the compound include alkoxides, hydrolysates of alkoxides, carboxylates, acetylacetonate salts, chlorides, sulfates, and nitrates of elements constituting the oxide.

In order to increase the viscosity of the solution containing the compound of the elements constituting the oxide, a thickener such as polyethylene glycol may be added.

As a method for applying a solution containing a compound of the elements constituting the oxide, it is desirable to use a dip coating method, a spraying method, etc., and the application process may be repeated multiple times to adjust the thickness of the oxide layer. good.

According to the present invention, the step of coating the surface of the heat-resistant ceramic fiber on which the oxide layer is formed with the organometallic compound solution having the superconducting oxide composition and then firing the fiber can be repeated multiple times. Alternatively, after coating the surface of the heat-resistant ceramic fiber on which the oxide layer is formed with the organometallic compound solution having the superconducting oxide composition, drying or preliminary firing at a low temperature may be performed, and then firing may be performed. good. In addition, after coating and drying,
Alternatively, the step of pre-baking may be performed multiple times and then baking may be performed, and furthermore, the coating, drying, pre-baking, and baking may be repeated multiple times.

Preferably, the preliminary firing is performed at a temperature of about 200 to 600°C.

For the drying, a suitable method selected from heat drying, vacuum drying, freeze drying, etc. can be used.

Further, it is preferable that the organometallic compound solution having the superconducting oxide composition is blended so as to become an oxide superconducting ceramic upon firing.

The organometallic compound solution having a superconducting oxide composition contains at least rare earth elements, thallium, thallium and lead, bismuth,
The solution is preferably an organic compound of an element selected from the group consisting of bismuth and aluminum, bismuth and lead, bismuth and potassium, bismuth and yttrium, an alkaline earth metal, and copper. Furthermore, oxide powder may be mixed into the organic compound solution. In this case, the oxide powder preferably has an oxide superconducting structure, and is advantageously obtained by thermally decomposing a solution consisting of the organic compound.

Furthermore, the organic compound includes at least rare earth elements, thallium, elements selected from the group consisting of thallium and lead, bismuth, bismuth and aluminum, bismuth and lead, bismuth and potassium, bismuth and yttrium, alkaline earth metals, and copper. alkoxide, alkoxide hydrolyzate,
At least one selected from oleate, naphthenate, acetate, formate, gluconate, stearate, octanoate, probionate, and butyrate can be used.

Furthermore, the organometallic compound solution having a superconducting oxide composition used in the present invention includes a first component consisting of a solution in which at least one alkaline earth metal is dissolved in an organic solvent and a carboxylic acid, and a rare earth element, thallium. , thallium and lead, bismuth,
a second component consisting of at least one selected from organic solvent solutions of alkoxides of elements selected from the group consisting of bismuth and aluminum, bismuth and lead, bismuth and potassium, bismuth and yttrium, or carboxylates of these elements; and a third component consisting of an amine solution of copper carboxylate can be used.

The first component carboxylic acid is preferably at least one selected from formic acid, acetic acid, propionic acid, butyric acid, etc., and propionic acid is preferred.

As the organic solvent of the first component, at least one selected from various alcohols, toluene, benzene, hexane, xylene, etc. can be used, and toluene is particularly preferred.

The organic solvent of the second component can be at least one selected from various alcohols, toluene, benzene, hexane, xylene, etc., with toluene being preferred; , acetate are preferred.

The copper carboxylate of the third component is preferably copper acetate, and the amine of the third component can be ethylamine, isoprobylamine, aniline, etc.
Isoprobylamine is preferably used.

According to the present invention, the concentration of the solution made of the organometallic compound having an oxide superconducting composition is preferably 2 to 35% by weight in terms of the oxide superconducting ceramic. If the concentration of the solution is lower than 2% by weight, a sufficient film thickness of the oxide superconducting ceramic will not be obtained and the superconducting properties will deteriorate. It is necessary to increase the number of coatings with a solution made of a metal compound, making the process complicated. Further, the concentration of the solution is 3
If it is higher than 5% by weight, the viscosity becomes high and coating is difficult, and the film of the solution made of the organometallic compound having the oxide superconducting composition becomes non-uniform, resulting in a decrease in superconducting properties.

The method of coating the heat-resistant ceramic fibers with a solution of an organometallic compound having an oxide superconducting composition used in the present invention is preferably a dipping method or a spraying method.

The immersion method is a method in which the heat-resistant ceramic fiber is immersed in a solution consisting of a metal compound having the oxide superconducting composition and then pulled up, and the spray method is a method in which the heat-resistant ceramic fiber is pulled up after the heat-resistant ceramic fiber is immersed in a solution consisting of a metal compound having the oxide superconducting composition. The coating is applied by spraying a solution consisting of an organometallic compound having the above-mentioned oxide superconducting composition onto the organic ceramic fiber.

Alternatively, a solution made of an organometallic compound having the oxide superconducting composition may be applied using a roll coater or the like.

The temperature for firing carried out in the present invention is 750°C
It is preferable that it is above. This is because at a temperature lower than this, it is difficult to sinter the oxide superconducting ceramic densely, and it is difficult to obtain a superconducting ceramic wire with excellent superconducting properties.

Example Next, examples of the present invention will be described.

Example 1 1) 75 parts by weight of propionic acid were added to 155 parts by weight of toluene and mixed, and then 11 parts by weight of metallic barium was added and mixed to form a uniform solution.

2) Add yttrium butyrate 13 to the solution obtained in l).
Parts by weight were added and mixed to form a homogeneous solution.

3) 24 parts by weight of copper acetate monohydrate and 3 parts by weight of isoprobylamine
5 parts by weight to form a homogeneous solution, and this solution and the solution obtained in 2) were added and mixed to form a homogeneous solution. 4) 100 parts by weight of the solution obtained in 3) was concentrated to 71 parts by weight using a rotary evaporator at a temperature of 70°C to obtain a homogeneous solution.

5) After immersing alumina fiber (fiber diameter 15 μm) in 100% titanium tetraisobutoxide,
C. for 10 minutes.

6) After repeating the step 5) 25 times, heat treatment was performed at 900° C. for 1 hour to form a titanium oxide layer with a thickness of 0.25 μm.

7) The fiber obtained in 6) was immersed in the solution obtained in 4) to coat the surface of the alumina fiber with the solution, and then heated at 70°C for 10 minutes and then at 120°C.
The sample was dried for 10 minutes, and then baked in air at a temperature of 500° C. for 10 minutes.

8) After repeating step 7) 15 times, heat to 000℃ in air.
Heat treatment was performed at a temperature of 1 hour.

9) The process of 7) and 8) was further repeated 5 times on the wire obtained in 8), and then heat treated at a temperature of 900° C. for 24 hours to produce a superconducting ceramic wire of the present invention having a diameter of 32 μm.

The thus obtained superconducting ceramic wire of the present invention was cut into a certain length, and the change in electrical resistance in zero magnetic field was measured while controlling the temperature of the test piece for measuring superconducting properties. In addition, current density was measured in liquid nitrogen. These results are shown in Table I.

Example 2 l) 50 parts by weight of ethyl alcohol and 50 parts by weight of toluene were added to 4.7 parts by weight of yttrium butyrate, 7.0 parts by weight of barium ethylate, and 9.2 parts by weight of copper acetate to create a homogeneous solution. .

2) Strontium metal 0. 0.07 mol of titanium tetraisopropoxide and 0.07 mol of titanium tetraisopropoxide were dissolved in 300 g of 2-ethoxyethanol to form a homogeneous solution, and this solution was concentrated using an evaporator until it reached 100 g.

3) After immersing alumina fiber (fiber diameter 15 μm) in the solution obtained in 2) above and pulling it up,
Heat treatment was performed at ℃ for 10 minutes.

4) After repeating the step 3) above 40 times, heat to 1000°C.
A strontium titanate layer having a thickness of 0.2 μm was formed by heat treatment for 1 hour.

5) Using the solution obtained in step 1) above and the fiber obtained in 4) above, the same treatments as in 7) to 9) of Example 1 were performed to create a superconducting ceramic wire with a diameter of 26 μm. The critical temperature and critical current density in zero magnetic field were measured in the same manner as in Example 1, and are shown in Table 1.

Example 3 I) 100 parts by weight of probionic acid was added to 100 parts by weight of toluene and mixed, and then 35 parts by weight of metallic strontium was added, heated and mixed to form a uniform solution.

2) After adding 10'O parts by weight of probionic acid to 100 parts by weight of toluene and mixing, 17 parts by weight of metallic calcium was added, heated and mixed to form a uniform solution.

3) After adding and mixing 50 parts by weight of probionic acid to 50 parts by weight of toluene, 16 parts by weight of lead oxide was added, heated, and mixed to form a uniform solution.

4) 167 parts by weight of bismuth butyrate was added to the solution obtained in 3), heated and mixed to form a homogeneous solution.

5) The solutions obtained in 1) and 2) were heated and mixed to form a homogeneous solution, and then added to the solution obtained in 4) and mixed to form a homogeneous solution.

6) 130 parts by weight of copper acetate monohydrate was dissolved in 300 parts by weight of isopropylamine to form a homogeneous solution.

7) The solution obtained in 6) was added to the solution obtained in 5) and mixed to form a homogeneous solution.

8) 100 parts by weight of the solution obtained in 7) was concentrated to 80 parts by weight using a rotary evaporator to obtain a homogeneous solution.

9) 4wt% in 20wt% magnesium chloride aqueous solution
Silicon carbide fibers (fiber diameter 14 μm) were immersed in a solution containing polyethylene glycol, and then heat-treated at 500° C. for 10 minutes.

10) After repeating the step 9) 20 times, the temperature at 900°C
Heat treatment was performed for 1 hour to form a layer of magnesium oxide with a thickness of 0.25 μm.

If) A superconducting ceramic wire of the present invention having a diameter of 23 μm was prepared in the same manner as in 7) to 9) of Example 1 below, and the critical current density in zero magnetic field was measured in the same manner as in Example 1. It is shown in Table 1.

Example 4 l) 200 parts by weight of propionic acid were added to 200 parts by weight of toluene and mixed, and then 110 parts by weight of metallic barium was added to form a homogeneous solution.

2) After adding and mixing 200 parts by weight of probionic acid to 200 parts by weight of toluene, 32 parts by weight of metallic calcium was added and mixed to form a homogeneous solution.

3) After mixing the solutions obtained in 1) and 2), 1000 parts by weight of propionic acid was added to 1000 parts by weight of toluene and mixed to form a homogeneous solution.

4) 211 parts by weight of thallium acetate was added to the solution obtained in 3) and mixed to form a homogeneous solution.

5) Dissolve 240 parts by weight of copper acetate monohydrate in 500 parts by weight of isoprobylamine to make a homogeneous solution, and add 4 parts by weight to this solution.
) was added and mixed to make a homogeneous solution.

6) 100 parts by weight of the solution obtained in 5) was concentrated to 75 parts by weight using a rotary evaporator to make a homogeneous solution67
) 3 wt% in an aqueous solution of 20 wt% magnesium sulfate
Zirconia fibers (fiber diameter 15 μm) were immersed in a solution containing polyethylene glycol, and then heated to 500°C.
It was heat-treated for 10 minutes.

8) After repeating the step 7) 20 times, heat treatment was performed at 900° C. for 1 hour to form a layer of magnesium oxide with a thickness of 0.2 μm.

9) A superconducting ceramic wire of the present invention having a diameter of 30 μm was created by the same method as in 7) to 9) of Example 1 below,
The critical temperature and critical current density in zero magnetic field were measured in the same manner as in Example 1, and are shown in Table 1.

Table 1 Examples l 2 3 4 Critical temperature (K)
91 90 104 103 (Effects of the Invention) As described above, according to the present invention, a superconducting ceramic wire with excellent flexibility, superconducting properties, and mechanical strength can be easily manufactured, and the obtained Superconducting ceramic wires are highly practical materials in various fields such as electronics, energy, and medical fields, and are industrially useful.

Claims (1)

[Claims] 1. A heat-resistant ceramic fiber, an oxide layer formed around the heat-resistant ceramic fiber and mainly containing titanium or magnesium, and an oxide superconducting ceramic covering the oxide layer. A superconducting ceramic wire consisting of. 2. The superconducting ceramic wire according to claim 1, wherein the oxide layer is at least one selected from titanium oxide, strontium titanate, and magnesium oxide. 3. Claim 1, wherein the oxide layer has a thickness of 2 μm or less.
Alternatively, the superconducting ceramic wire according to 2. 4. The heat-resistant ceramic fiber has a diameter of 40μ
The superconducting ceramic wire according to claim 1, which is a long fiber having a length of less than m. 5. The superconducting ceramic wire according to any one of claims 1 to 4, wherein the heat-resistant ceramic fiber has a heat resistance temperature of 750°C or higher. 6. The oxide superconducting ceramic is Y-based, Bi-based,
Claim 1: At least one species selected from Tl series.
5. The superconducting ceramic wire according to item 5. 7. The superconducting ceramic wire according to any one of claims 1 to 6, wherein the superconducting ceramic wire has a diameter of 80 μm or less. 8. After forming an oxide layer containing mainly titanium or magnesium on the surface of the heat-resistant ceramic fiber,
1. A method for producing a superconducting ceramic wire, comprising coating with a solution consisting of an organometallic compound having an oxide superconducting composition, and then firing. 9. The method for manufacturing a superconducting ceramic wire according to claim 8, wherein the oxide layer is formed by heat treating a solution containing mainly titanium or magnesium. 10. The method for producing a superconducting ceramic wire according to claim 8 or 9, characterized in that the step of coating with a solution made of an organometallic compound having the oxide superconducting composition and then firing the wire is repeated multiple times. 11. The concentration of the solution consisting of the organometallic compound having the oxide superconducting composition is 2 when converted to the oxide superconducting ceramic.
The method for producing a superconducting ceramic wire according to claim 8 or 9, wherein the content is 35% by weight. 12. The method for manufacturing a superconducting ceramic wire according to claims 8 to 11, wherein the firing temperature is 750°C or higher.