JP7553932B2 - Superconducting joint structure of oxide superconductor and superconducting device using the same - Google Patents

Description

The present invention relates to a superconducting connection structure for oxide superconductors, and in particular to a superconducting connection structure for oxide superconductors that utilizes a liquid alloy containing gallium, indium, and tin.

To connect devices that utilize superconductivity, such as superconducting wires, superconducting coils, superconducting cavities, and superconducting electronic elements, while maintaining the superconducting state, the connecting parts must also exhibit superconductivity. Connecting such superconductors while maintaining the superconducting state is called a superconducting connection (or superconducting junction), and can be realized mainly in the following two ways.

(A) A mode in which an alloy that has a low melting point like solder and exhibits superconductivity at low temperatures (such as an alloy containing lead and bismuth, tin, bismuth and indium, tin, lead and bismuth, tin and indium, or tin and bismuth) is sandwiched between two superconductors and the connection is made by raising the temperature above the melting point (see, for example, Patent Documents 1 and 2).
(i) A mode in which two superconductors are connected by growing crystals of the superconductor itself between them.

In the above (a), heat treatment is required to melt the alloy sandwiched between the two superconductors and bond the alloy and the superconductors.
In the above (i), heat treatment is required to grow the crystals of the superconductor itself on top of the superconductor and bond them to another superconductor.
An electric furnace is required for the heat treatment, and some devices using superconductivity may not be able to withstand the increased temperature, or a special electric furnace may need to be prepared. In particular, if the superconductor is an oxide superconductor, the oxygen content may change due to the heat treatment, and the oxide superconductor itself may be altered. Therefore, it would be ideal to achieve a superconducting connection without heat treatment, and it would be necessary to sandwich between two oxide superconductors a superconductor with a melting point lower than room temperature or a material that grows as a superconductor at a temperature lower than room temperature.

On the other hand, Patent Document 3 discloses that some compositions of alloys containing gallium, indium, and tin become liquid alloys. And Non-Patent Document 1 discloses that some compositions of alloys containing gallium, indium, and tin become superconductors.
However, to the best of the inventor's knowledge, there have been no reports of superconducting connections using liquid alloys containing gallium, indium, and tin. In particular, oxide superconductors are brittle, and therefore have the problem that processing of superconducting connections is more difficult than coil connections using metal-based superconductors such as alloys containing niobium and titanium.
Furthermore, when Galinstan disclosed in Patent Document 3 is used, according to Non-Patent Document 1, the following problems arise.
(1) Since the target is printed electronics, it is very laborious because it uses an alloy containing gallium, indium, and tin processed into nanometer-sized droplets (nanodroplets).
(2) The composition of galinstan, expressed in atomic percent _{, is Ga41.64In39.61Sn18.75 , and} its melting point, whether in droplet or bulk form, is about 63°C. Even when heated above room temperature to liquefy it, it must be heated to above 60°C. This makes it less versatile than liquid alloys containing gallium, indium, and tin.
(3) Superconductivity is believed to occur when gallium, indium, and tin (element metals) are precipitated at low temperatures. Element metals are type I superconductors, and compared to type II superconductors, their critical magnetic field is smaller, making them disadvantageous in practical use.

USP No. 3156539 JP 9-82445 A Patent No. 2574658

L. Ren et al., Adv. Functional. Mater. 26 (2016) 8111.

The conventional technologies disclosed in Patent Documents 1 and 2 require heat treatment to connect two oxide superconductors to create a superconducting connection through which current flows with zero electrical resistance, and require heat treatment equipment and heat treatment conditions to be set taking into account the physical properties of the oxide superconductors that are the subject of the superconducting connection, making them less versatile.
In addition, when connecting two oxide superconductors, whether using a low melting point alloy or connecting by crystal growth, the surface of the oxide superconductor needs to be flattened, but polishing the surface of the oxide superconductor to the required flatness takes time. In particular, when using crystal growth, it is necessary to create a clean surface so that the crystals can grow, and careful polishing is required.
Some of the elements that make up low-melting point alloys contain toxic lead, and sales of such products are restricted by the RoHS (Restriction of the use of certain Hazardous Substances in Electrical and Electronic Equipment) Directive, and sales of lead-containing products within the EU are prohibited.
The present invention has been made to solve the above-mentioned problems, and aims to provide a superconducting connection structure that does not require surface polishing or heat treatment when connecting oxide superconductors, and that does not contain lead, and a superconducting device using the same.

[1] The present invention relates to a superconducting connection structure for oxide superconductors, in which a liquid alloy containing gallium, indium, and tin is sandwiched between two oxide superconductors.

[2] In the superconducting connection structure of the oxide superconductor of the present invention, preferably, the composition of the low melting point alloy containing gallium, indium and tin, which has a melting point temperature of 60° C. or less in a thermal equilibrium state, is Ga _x In _y Sn _z , where x, y and z are expressed in atomic percent, the composition satisfies the range surrounding the following points (x, y, z) on a ternary phase diagram of gallium, indium and tin.
(90, 5, 5), (70, 5, 25), (60, 10, 30), (50, 17, 33), (45, 23, 32), (40, 30, 30), (39, 35, 26), (43, 36, 21), (50, 35, 15), (54, 36, 10), (54, 41, 5) and (90, 5, 5).
[3] In the superconducting connection structure of the oxide superconductor of the present invention, the composition of the liquid alloy containing gallium, indium and tin is preferably Ga _x In _y Sn _z , where x, y and z are expressed in atomic percent, and satisfy the following ranges:
55≦x≦90, 5≦y≦25, 5≦z≦20 and x+y+z=100.
[4] In the superconducting connection structure of the oxide superconductor of the present invention, the composition of the liquid alloy containing gallium, indium and tin is preferably Ga _x In _y Sn _z , where x, y and z are expressed in atomic percent, and satisfy the following ranges:
55≦x≦88, 5≦y≦25, 7≦z≦20 and x+y+z=100.
[5] In _the superconducting connection structure of the oxide superconductor of the present invention, the oxide superconductor is preferably one selected from the group consisting of yttrium-based copper oxide superconductors { _{YBa2Cu3O6 +δ} (δ indicates the amount of oxygen deficiency, the same applies below)), bismuth-based copper oxide superconductors { _{Bi2Sr2Ca n - 1CunO2n +4+δ} (n = 1, 2 or 3)}, and rare earth element-based _copper oxide superconductors { _{REBa2Cu3O6 +δ} (RE is a rare earth element)}.
[6] In the superconducting joint structure of the oxide superconductor of the present invention, the oxide superconductor may be preferably changed to one selected from the group consisting of iron-based superconductors {REFeAsO _1-X F _X (RE is a rare earth element), AFe ₂ As ₂ (A is an alkali metal or an alkaline earth metal), and AFeAs}.

[7] A superconducting device of the present invention has the above-mentioned superconducting joint structure of the oxide superconductor.
[8] In the superconducting device of the present invention, the superconducting device preferably includes at least one of a superconducting wire, a superconducting coil, a superconducting cavity, and a superconducting electronic element.
[9] In the superconducting device of the present invention, preferably, the superconducting device is any one of a nuclear magnetic resonance imaging device, a nuclear magnetic resonance spectrometer, a superconducting magnet, a superconducting power transmission line, a superconducting filter for high frequency communication, a SQUID, a magnetic field detector, a superconducting linear motor, or a superconducting electromagnetic propulsion device for a ship.

The present invention has the following advantages.
(i) The precipitation of superconductors from a liquid alloy containing gallium, indium, and tin at or below room temperature is utilized, eliminating the need for heat treatment to create superconducting connections and avoiding deterioration of oxide superconductors due to heat treatment.
(ii) Since a superconducting joint can be made by simply applying a liquid alloy containing gallium, indium and tin, a superconducting joint can be easily made even over a large area, regardless of the shape of the oxide superconductor.
(iii) Liquid and solid alloys containing gallium, indium and tin can be synthesized by simply mixing gallium, indium and tin (each of which is an elemental metal) at room temperature through a eutectic reaction or by heat treatment at 60° C. or less. This does not require any special equipment for synthesis.
(iv) Even when using an alloy containing solid gallium, indium, and tin, no special equipment is required since the alloy can be prepared at a temperature of 60° C. or less. Therefore, if there is an apparatus for applying a liquid alloy containing gallium, indium, and tin or an apparatus for heating a solid alloy containing gallium, indium, and tin at a temperature of 60° C. or less, it is possible to prepare a superconducting connection on the spot regardless of location.
(v) By using a liquid alloy containing gallium, indium and tin to connect two oxide superconductors, it is not necessary to polish the surface of the oxide superconductors. In addition, the liquid alloy containing gallium, indium and tin does not contain toxic lead, so it has a low environmental impact.
(vi) In the superconducting connection structure of the oxide superconductor of the present invention, an alloy containing indium and tin, which is a type II superconductor, is precipitated, and therefore the critical magnetic field is larger than that of the simple metal, which is a type I superconductor, disclosed in Non-Patent Document 1, and this is advantageous in practical use.

The melting point isotherm of a ternary alloy of gallium, indium and tin is shown. 1 is a diagram showing the melting point isotherms of ternary alloys of gallium, indium and tin, with an expanded range being shown for the liquid and low melting alloys preferred for use in the present invention. The structure formed by cooling a liquid alloy containing gallium, indium and tin is shown, along with a gallium phase and an alloy containing indium and tin. 1 is a phase diagram of a binary alloy of indium and tin. FIG. 1 is a cross-sectional view of a superconducting joint of an oxide superconductor using a liquid alloy containing gallium, indium, and tin according to an embodiment of the present invention, in which the oxide superconductor is YBa ₂ Cu ₃ O ₇ and is of a butt joint type. FIG. 6 is a diagram showing the temperature change in electrical resistance of a superconducting joint of the oxide superconductor shown in FIG. 5 . FIG. 6 is a diagram showing current-voltage characteristics of a superconducting connection of the oxide superconductor shown in FIG. 5 . FIG. 2 shows a cross-sectional structure of a superconducting joint of an oxide superconductor using a liquid alloy containing gallium, indium, and tin according to a second embodiment of the present invention, in which the oxide superconductor is Bi ₂ Sr ₂ CaCu ₂ O _8+δ and shows a stack type. FIG. 9 is a diagram showing the temperature change in electrical resistance of a superconducting joint of the oxide superconductor shown in FIG. 8 . FIG. 9 is a diagram showing current-voltage characteristics of a superconducting connection of the oxide superconductor shown in FIG. 8 . FIG. 13 is a diagram showing a superconducting connection structure of an oxide superconductor according to another embodiment of the present invention.

Ternary alloys containing gallium, indium, and tin, with a composition in which the melting point temperature in a thermal equilibrium state is preferably 60°C or less, more preferably 40°C or less, and particularly preferably 23°C or less, have a lower melting point than alloys used in conventional superconducting connections, so that even if the alloy containing gallium, indium, and tin is in a composition range in which it does not become liquid at room temperature, it is possible to create a superconducting connection at a temperature low enough that the oxide superconductor does not change. In particular, ternary alloys containing gallium, indium, and tin within a specific composition range have a melting point (freezing point) below room temperature due to a eutectic reaction, so they become liquid at room temperature. Furthermore, ternary alloys containing gallium, indium, and tin may contain 0.8 atomic percent or less of bismuth and 1.4 atomic percent or less of antimony.

Figure 1 shows the melting point isotherms of a ternary alloy of gallium, indium and tin. Figure 2 shows the phase diagram of a ternary alloy of gallium, indium and tin, with an expanded range of the alloy being preferred for use in the present invention. The melting point distribution curves in Figures 1 and 2 are taken from the "ASM Alloy Phase Diagram Database" and the original source is as follows:
Kononenko VI, and Yatsenko SP, Equilibrium diagrams characterization of binary and ternary gallium systems with I-VI elements on deviation of liquid alloys structural-susceptible properties, Diagrammy Sostoyaniya Met. Sist., Mater. Vses. Soveshch., 4th, Vol. , 1971, p 254-257

The melting point distribution curves in Figures 1 and 2 are measured for a mixture of the raw materials gallium, indium, and tin (all solids). In contrast, Galinstan and the inventor's experiments measured the raw materials gallium, indium, and tin that were mixed and melted to form a liquid metal. Therefore, the liquid metal becomes supercooled below the melting point (freezing point).
In the present invention, the region of the composition range in which the melting point temperature in a thermal equilibrium state is 60° C. or less is preferably the range surrounding the following points (x, y, z) on the ternary phase diagram of gallium, indium and tin, where Ga _x In _y Sn _z is used, and x, y and z are expressed in atomic percent (the range surrounded by the thick line in FIG. 1): (90, 5, 5), (70, 5, 25), (60, 10, 30), (50, 17, 33), (45, 23, 32), (40, 30, 30), (39, 35, 26), (43, 36, 21), (50, 35, 15), (54, 36, 10), (54, 41, 5) and (90, 5, 5).

Next, the elements used in the liquid alloy of the present invention will be described.
Gallium: 39 atomic percent≦x≦90 atomic percent (when melting point temperature is 60° C. or less)
At room temperature and pressure, orthorhombic alpha gallium (specific gravity 5.9) is stable and is a bluish metallic luster metal. Its melting point is low at 29.8°C. It has three valence electrons (4s, 4p), but the 3d orbital is also relatively shallow.
Liquid metals have a strong tendency to become supercooled below their melting (freezing) point, and when Ga is made into nanoparticles, it can remain liquid even at 90 Kelvin. When crystals are seeded, it begins to freeze. By sealing gallium in a glass tube, it can be used as a high-temperature thermometer, similar to a mercury thermometer. Liquid gallium metal wets glass and skin. Below the critical temperature of 1.10 Kelvin, gallium becomes a superconductor.
Since gallium is expensive, the composition ratio is preferably in a range close to the lower limit of 39 atomic percent, for example, in the range of 56 atomic percent to 78 atomic percent, and more preferably in the range of 60 atomic percent to 70 atomic percent.
Based on a ternary phase diagram of gallium, indium and tin, gallium may be, for example, in the range of 55 atomic percent to 90 atomic percent, more preferably in the range of 55 atomic percent to 88 atomic percent.

Indium: 5 atomic percent≦y≦41 atomic percent (when melting point temperature is 60° C. or less)
It has a tetragonal crystal structure (specific gravity 7.3) and is a soft silver-white metal. Its melting point is low at 156.4°C and it is stable in air. At a critical temperature of 3.37K or less, indium becomes a superconductor. Indium has excellent malleability and ductility.
Since indium is expensive, the composition ratio is preferably close to the lower limit of 5 atomic percent, for example, 6 atomic percent to 18 atomic percent, more preferably 6 atomic percent to 10 atomic percent. On the other hand, if the composition ratio of indium is increased, the ratio of _In3Sn , which has a high critical temperature, increases in the two types of eutectic structures of _In3Sn and _InSn4 , which is preferable in terms of superconducting connection performance.
When based on a ternary phase diagram of gallium, indium and tin, indium may range from 5 atomic percent to 25 atomic percent.

Tin: 5 atomic percent≦z≦33 atomic percent (when melting point temperature is 60° C. or less)
At room temperature and pressure, tetragonal beta tin (specific gravity 7.4) is stable and is a ductile silvery-white metal. On the other hand, alpha tin, which is stable below 13.2°C, is a brittle, gray nonmetallic substance with a diamond-type crystal structure. Since alpha tin is formed by covalent bonds, it does not have free electrons and does not have metallic properties. Thermodynamically, beta tin transforms to alpha tin at 13.2°C, but the reaction actually begins to progress in the low temperature range of -10°C, and the reaction rate reaches its maximum at -45°C.
Tin becomes a superconductor at a critical temperature of 3.73 K or less. Compared to gallium and indium, the current trading price is about 1/10 of theirs.
The proportion of tin is preferably in a range close to the upper limit of 33 atomic percent, for example, in the range of 15 atomic percent to 18 atomic percent, inclusive, so that the proportions of expensive gallium and indium may be lowered.
When based on a ternary phase diagram of gallium, indium and tin, tin may be in the range of 5 atomic percent to 20 atomic percent, more preferably 7 atomic percent to 20 atomic percent.

Bismuth: up to 0.8 atomic percent Bismuth has a beneficial effect on the fluidity of the alloy. A content of bismuth above 0.8 atomic percent causes a significant and undesirable increase in the melting point.
Antimony: up to 1.4 atomic percent Antimony improves oxidation resistance. Contents above 1.4 atomic percent of antimony cause a significant and undesirable increase in the melting point.
Antimony, like tin, is a readily available and inexpensive component, while gallium and indium are expensive.
The eutectic according to the invention may possibly have only a small content of impurities, such as lead or zinc, of less than 0.001 weight percent, preferably less than 0.0001 weight percent.

FIG. 3 shows the structure formed by cooling a liquid alloy containing gallium, indium and tin to form a gallium phase and an alloy containing indium and tin.
When a liquid ternary alloy containing gallium, indium and tin is applied to an oxide superconductor to bond two oxide superconductors and cooled to below room temperature, the liquid alloy containing gallium, indium and tin separates into two phases, a gallium phase and an alloy phase containing indium and tin, and the alloy phase containing indium and tin precipitates at intervals of, for example, 5 to 20 micrometers. This alloy containing indium and tin has an alloy structure containing at least one of the alloys In ₃ Sn and InSn ₄ depending on the composition ratio of indium and tin, and becomes a superconductor at or below the liquid helium temperature. Thus, a current can be passed between the two oxide superconductors through the alloy containing indium and tin while maintaining zero electrical resistance.

FIG. 4 is a phase diagram of a binary alloy of indium and tin.
In an alloy of tin and indium, two types of intermetallic compounds, In ₃ Sn and InSn _4, are produced. The critical temperature of _{In 3} Sn is 5.5 to 6.5 Kelvin, and that of InSn ₄ is 4.5 to 5.0 Kelvin. Since the critical temperatures of _{In 3} Sn and InSn ₄ are higher than the liquid temperature of helium, 4.2 Kelvin, they are responsible for the electrical pathway that realizes the superconducting connection between oxide superconductors.

Example 1
FIG. 5 is a diagram showing a cross-sectional structure of a superconducting joint of an oxide superconductor using a liquid alloy containing gallium, indium, and tin according to an embodiment of the present invention, in which the oxide superconductor is YBa ₂ Cu ₃ O _6+δ and is a butt joint type. Here, δ indicates the amount of oxygen vacancy, and is in the range of 0≦δ≦2, for example. In oxide superconductors, there is a correlation between an increase in the amount of oxygen and an increase in the hole concentration. Ideally, 6+δ is 7, but it may be a little larger than 7. From a crystallographic point of view, if oxygen is filled in all the missing oxygen positions, 6+δ becomes 8, so 0≦δ≦2 is used. Incidentally, YBa ₂ Cu ₃ O _6+δ may also be expressed as YBa ₂ Cu ₃ O _7-δ (where -1≦δ≦1).
In the figure, two oxide superconductors 10 and 12 are sintered bodies of _{YBa2Cu3O6 +δ} oxide superconductor. The liquid alloy 20 _{is Ga78In15Sn7} , and the dimensions of the liquid alloy 20 are 0.5 mm in width, 4 mm in depth, and 1 mm in height. The two oxide superconductors 10 and ₁₂ are butt-jointed by _the liquid alloy 20. That is, the two oxide superconductors 10 and 12 are electrically connected by the liquid alloy 20 at the opposing ends in the longitudinal direction.

Fig. 6 is a diagram showing the temperature change in electrical resistance of the superconducting joint shown in Fig. _5. The electrical resistance decreases near 90 K, which is the superconducting transition temperature of the _{YBa2Cu3O6 +δ} oxide superconductor, and becomes zero near the liquid helium temperature, and below this temperature the superconducting joint shows superconductivity.

Figure 7 shows the current-voltage characteristics at 3.4 Kelvin of the superconducting connection shown in Figure 5. At currents below 0.3 milliamperes, current flows with the voltage remaining at zero, indicating that a superconducting connection is realized below this current.

Example 2
8 is a diagram showing the cross-sectional structure of a superconducting joint of an oxide superconductor using a liquid alloy containing gallium, indium and tin according to a second embodiment of the present invention, in which the oxide _{superconductor is Bi2Sr2CaCu2O8 + δ} , and shows a stack type. Here, δ indicates the amount of oxygen vacancy, and is in the range of 0≦δ _≦ 2, for example. Since the crystal structure of bismuth-based materials is complicated (because they have a modulated structure), the amount of oxygen vacancy itself is not well understood. From a crystallographic point of view, if oxygen were to be filled in all the missing oxygen positions, 8+δ would be 10, so 0≦δ≦2 is set.
In the figure, two oxide superconductors 30, 32 are sintered bodies of _{Bi2Sr2CaCu2O8 +δ} oxide superconductor. The liquid alloy 40 _{is Ga78In15Sn7} , and the dimensions of the liquid alloy 40 are 2 mm in width, ₂ mm in depth, and 0.1 _mm in height _. The two oxide superconductors 30, 32 are joined by the liquid alloy 40 in an overlapping state. That is, the two oxide superconductors 30, 32 are electrically connected by the liquid alloy 40 so that the opposing ends in the longitudinal direction are partially overlapped.

Fig. 9 is a diagram showing the temperature change in electrical resistance of the superconducting joint shown in Fig. _8. The electrical resistance decreases near 80 K, which is the superconducting transition temperature of the _{Bi2Sr2CaCu2O8 +δ oxide} superconductor, and becomes zero near the liquid helium temperature. Below this temperature, the superconducting joint shows superconductivity.

Figure 10 shows the current-voltage characteristics at 3.4 Kelvin of the superconducting connection shown in Figure 8. At currents of 0.025 amperes or less, current flows with the voltage remaining at zero, indicating that a superconducting connection is realized below this current.

11 is a diagram showing a superconducting joint structure of oxide superconductors according to another embodiment of the present invention. The superconducting joint structure of oxide superconductors can be of (A) butt type, (B) lap type, and (C) indirect joint.
(A) and (B) are direct bonds, in which the bonding part is made of the same material as the superconductor. (C) Indirect bonds are bonds in which the bonding part is made of a material different from the superconductor.

In the above examples, YBa ₂ Cu ₃ O _6+δ oxide superconductor and Bi ₂ Sr ₂ CaCu ₂ O _8+δ oxide superconductor are shown as oxide superconductors, but the oxide superconductor of the present invention is not limited to these and may be a Bi ₂ Sr ₂ Ca _n-1 Cu _n O _2n+4+δ (n=1 or 3) oxide superconductor, a rare earth element barium copper oxide superconductor {REBa ₂ Cu ₃ O _6+δ or REBa ₂ Cu ₃ O _7-δ (RE is a rare earth element)}, an iron-based superconductor {REFeAsO _1-X F _X , AFe ₂ As ₂ (A is an alkali metal or an alkaline earth metal), AFeAs}.

The superconducting connection structure of the oxide superconductor of the present invention provides a superconducting connection structure that does not require heat treatment, and is therefore suitable for use in nuclear magnetic resonance imaging devices, nuclear magnetic resonance spectroscopy devices, superconducting magnets, power transmission lines, superconducting filters for high-frequency communication, SQUIDs, magnetic field detectors, superconducting linear motors, or motors for ship propulsion.

10, 12 Oxide superconductor {YBa ₂ Cu ₃ O _6+δ }
20 Liquid metal layer (Ga ₇₈ In ₁₅ Sn ₇ )
30, 32 Oxide superconductor {Bi ₂ Sr ₂ CaCu ₂ O _8+δ }
40 Liquid metal layer (Ga ₇₈ In ₁₅ Sn ₇ )

Claims (7)

In a superconducting connection structure of oxide superconductors, a liquid alloy made of gallium, indium, and tin or a low-melting-point alloy having a composition range in which the melting point temperature in a thermal equilibrium state is 60° C. or less is sandwiched between two oxide superconductors,
The liquid alloy consisting of gallium, indium and tin or the low melting point alloy having a composition range in which the melting point temperature in a thermal equilibrium state is 60° C. or less is a composition of Ga _x In _y Sn _z , where x, y and z are expressed in atomic percent, the composition satisfies the following range.
60≦x≦70, 5≦y≦25, 5≦z≦20 and x+y+z=100. In a superconducting connection structure of oxide superconductors, a liquid alloy consisting of essential elements of gallium, indium, and tin, and optional elements of bismuth of 0.8 atomic percent or less and antimony of 1.4 atomic percent or less, or a low-melting-point alloy having a composition range in which the melting point temperature in a thermal equilibrium state is 60° C. or less is sandwiched between two oxide superconductors,
A superconducting connection structure, characterized in that the liquid alloy or the low melting point alloy has a composition of Ga _x In _y Sn _z , where x, y and z are expressed in atomic percent and satisfy the following ranges:
60≦x≦70, 5≦y≦25, 5≦z≦20, and x+y+z={100−[bismuth composition ratio]−[antimony composition ratio]}. The superconducting connection structure described in claim ₁ or _{2 ,} characterized in that the oxide superconductor is one selected from the _group consisting of yttrium-based copper oxide high-temperature superconductors ( _{YBa2Cu3O6 +δ} , δ indicates the amount of oxygen deficiency), bismuth-based copper oxide superconductors {Bi2Sr2Ca _{n- 1CunO2n+4+δ} (n = 1, 2 or 3)}, and rare earth element-based copper oxide superconductors { _{REBa2CuO6 +δ} (RE is a rare earth element)}. The superconducting joint structure according to claim 1 or 2, characterized in that the oxide superconductor is one selected from the group consisting of iron-based superconductors {REFeAsO _1-x F _x (RE is a rare earth element), AFe ₂ As ₂ (A is an alkali metal or an alkaline earth metal), and AFeAs}. A superconducting device having a superconducting connection structure of an oxide superconductor according to any one of claims 1 to 4. The superconducting device according to claim 5, characterized in that the superconducting device includes at least one of a superconducting wire, a superconducting coil, a superconducting cavity, and a superconducting electronic element. The superconducting device according to claim 5 or 6, characterized in that the superconducting device is any one of a nuclear magnetic resonance imaging device, a nuclear magnetic resonance spectrometer, a superconducting magnet, a superconducting power transmission line, a superconducting filter for high-frequency communication, a SQUID, a magnetic field detector, a superconducting linear motor, and a superconducting electromagnetic propulsion device for ships.