JP2907313B2 - Bismuth-based high-temperature superconductor joining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining bismuth-based high-temperature superconductors.

[0002]

2. Description of the Related Art Conventionally, high-temperature superconductors mainly composed of fine ceramics are very difficult to join by welding or the like, unlike metals. In other words, bismuth-based high-temperature superconductors, which are a type of fine ceramics, are vulnerable to thermal shock, and cracks will occur if joining is attempted simply by heating, making joining impossible in practice. A high-temperature superconductor having the following shape must be manufactured in an integrated structure from the beginning. Therefore, in order to manufacture a large-sized high-temperature superconductor, the equipment such as a sintering furnace must be increased in size, which increases the cost, and in particular, a large and complicated-shaped high-temperature superconductor maintains uniform quality. difficult. For such a reason, upsizing of the high-temperature superconductor has conventionally been limited.

[0003]

SUMMARY OF THE INVENTION Therefore, according to the present invention, a high-temperature superconductor having a large shape can be manufactured without using large-scale equipment by enabling joining of a bismuth-based high-temperature superconductor. It is a technical problem to be solved to ensure uniform quality even for a high-temperature superconductor having a large and complicated shape.

[0004]

The technical means for solving the above-mentioned problems are as follows: Bi, Sr, Ca and Cu
The mixed raw material of the compound is heated and melted, then cooled and solidified to the required shape.
And then heat-treated a plurality of Bi ₂ Sr ₂ CaCu ₂ O
Bonding of superconducting crystallized glass including x superconducting crystal
The process of heating the surface of the part to a molten state,
Directly butting each melted joint
The process and its directly butted joints are heated at the required temperature.
Bi ₂ Sr ₂ CaCu ₂ Ox superconductivity by heating
The step of melting and joining the crystals,
The superconducting crystallized glass in the closed state is heated at 700 ° C. to 880 ° C.
At the temperature of the required time in the air or oxygen-containing atmosphere
Heat, hold at the same temperature for the required time, and allow to cool naturally
Joining the superconducting crystallized glass by
It is.

[0005]

[Action] Including Bi ₂ Sr ₂ CaCu ₂ Ox superconducting crystal
Heat the surface of the joint of each superconducting crystallized glass
Melted, and then directly join the melted joints
After heating at the required temperature, Bi ₂ Sr
₂ CaCu ₂ Ox superconducting crystal is melted and joined, joining
The superconducting crystallized glass in a state of 700 ° C. to 880 ° C.
At the temperature of the required time in the air or oxygen-containing atmosphere
Heat, hold for the required time at that temperature, and let it cool naturally
And the joints are joined without cracks, and
The superconducting properties of the joint of
It was confirmed that the characteristics were the same as those of.

[0006]

Next, an embodiment of the present invention will be described. Commercially available special grade reagents (eg, Bi ₂ O _3, SrCO _3, CaCO _3, CuO such as oxides, carbonates, nitrates, and hydroxides)
Etc.) and the oxide ratio, Bi ₂ O ₃ : SrO:
It was weighed so that the molar ratio of CaO: CuO = 1: 2: 1: 2. After mixing these, the mixture was put into a crucible made of platinum, and heated and melted in an electric furnace maintained at 1000 ° C. to 1400 ° C. One end of a previously prepared quartz tube having an inner diameter of 3 mm was inserted into the melt, the melt was suctioned into the tube under reduced pressure from the opposite end, and then allowed to cool to room temperature. Next, by mechanically removing the external quartz tube, a rod-shaped molten solid containing a large amount of a glass phase was obtained.

Next, the rod-like solidified melt is heated to 700 ° C.
The mixture was heated at 880 ° C. in air or an atmosphere containing oxygen, kept at that temperature for 5 to 100 hours, and allowed to cool naturally to obtain a superconducting crystallized glass. This superconducting crystallized glass has been generated _{Bi 2 Sr} 2 CaCu 2 O _x superconducting crystal, glass phase was observed almost no residual. When the superconducting properties of the superconducting crystallized glass were measured, the critical temperature at which the electric resistance was zero was about 80 K (Kelvin), and the critical current density at 77 K at zero external magnetic field was about 80 A /
cm ² .

As shown in FIG. 1, two rod-shaped superconducting crystallized glasses 1, 1 are prepared, and these are joined in series. As shown in FIG. 2, when a commonly used Bunsen burner 2 heats the junction of superconducting crystallized glass 1 and 1, and only the surface is melted as shown in FIG. As shown in FIG. 4, the junctions of the superconducting crystallized glasses 1 and 1 are brought into contact. Thereafter, as shown in FIG. 5, the bonding portion in a contact state is heated by the Bunsen burner 2 to be sufficiently bonded.

In a state where the above-mentioned joints are sufficiently joined,
No cracks were found near the joint, and the joint was in a complete joined state. This joint is once heated to a high temperature and melted, and the Bi ₂ Sr ₂
The CaCu ₂ O _x superconducting crystal was melted and the glass phase was increased.

As described above, Bi ₂ Sr ₂ CaCu ₂ O _x
The superconducting crystallized glass 1, 1 having a junction where the superconducting crystal has melted and the glass phase has increased as shown in FIG. 6 is placed in an electric furnace (not shown) and heated at 700 ° C. to 880 ° C. in air or oxygen. Heating in an atmosphere containing
After holding for １００100 hours, the mixture was naturally cooled. The junction of the superconducting crystallized glass 1,1 thus heat-treated is Bi
₂ Sr ₂ CaCu ₂ O _x superconducting crystal is generated,
When the electric resistance was measured by the DC four-terminal method, the junctions were connected by a superconducting crystal, the critical temperature at which the electric resistance was zero was about 80 K (Kelvin), and the critical current density at 77 K at zero external magnetic field was about 80 A / It becomes cm ^2, and
Superconducting properties almost equal to those of superconducting crystallized glass 1, 1 before joining were obtained.

The solidified melt is treated at 700 ° C. to 880
The following problem arises when the above-mentioned step of heating at a temperature of 0 ° C. in the air or an atmosphere containing oxygen, maintaining the temperature at that temperature for 5 to 100 hours, and naturally cooling is omitted.
That is, after the quartz tube is mechanically removed, the ends of the two solidified melts are heated and melted by a Bunsen burner, joined, and then the joint is sufficiently joined by heating the joint. During the cooling in, cracks occurred near the joints, and complete joining could not be obtained. However, if the whole can be cooled slowly in a special electric furnace, the above-mentioned cracks are prevented from occurring, and perfect joining becomes possible.

The superconducting crystallized glasses 1 and 1 shown in FIG. 1 are not limited to the shape, but superconducting crystallized glasses 3 and 4 having different shapes can be joined as shown in FIG. 7, for example. Alternatively, it is possible to join not only two but also more superconducting crystallized glasses. Furthermore,
Not only a round shape but also a superconducting crystallized glass such as a square shape can be joined.

Next, a method of joining a high-temperature superconductor manufactured by a sintering method will be described. Commercially available high-grade reagents (eg, Bi ₂ O such as oxides, carbonates, nitrates, and hydroxides)
_3, SrCO ₃ . CaCO _3, an oxide ratio using the powder of CuO or the _{like), Bi 2 O 3: SrO} : CaO: CuO =
It was weighed so as to have a molar ratio of 1: 2: 1: 2. After mixing these, it is calcined by heating at 800 ° C for 24 hours,
Cooled to room temperature. This was pulverized, pressed into a prismatic shape (4 × 5 × 40 mm) at 200 MPa, placed in an electric furnace, and heated at 800 to 880 ° C. in air or an atmosphere containing oxygen. After holding for １００100 hours, the mixture was naturally cooled. By this manufacturing process, Bi ₂ Sr ₂ C
A prismatic ceramic made of aCu ₂ O _x superconducting crystal was obtained.

When the superconducting properties of the prismatic ceramics were measured, the critical temperature at which the electrical resistance was zero was about 80K.
(Kelvin), the critical current density at 77 K with no external magnetic field was about 80 A / cm ² , which was almost the same as that of the superconducting crystallized glass 1 described above.

Hereinafter, a joining method for preparing two prismatic ceramics and joining them will be described. still,
This joining process is performed substantially in the above-described superconducting crystallized glass 1,1.
The illustration is omitted because it is the same as the joining process. A generally used Bunsen burner heats the joint of each of the prismatic ceramics, and when only the joint surface is melted, the joints of each of the prismatic ceramics are brought into contact. After that, the contact portion in the contact state is heated by the Bunsen burner to be sufficiently joined.

When the joints were sufficiently joined, no cracks were observed near the joints, and the joints were completely joined. This joint portion was once heated to a high temperature and melted, and the Bi ₂ Sr ₂ CaCu ₂ O _x superconducting crystal generated in the prismatic ceramics was melted and the glass phase was increased.

As described above, Bi ₂ Sr ₂ CaCu ₂ O _x
The prismatic ceramic having the junction where the superconducting crystal is melted and the glass phase is increased is placed in an electric furnace, and the temperature is set to 700 ° C.
Heating at 80 ° C in air or oxygen-containing atmosphere,
After maintaining at that temperature for 5 to 100 hours, it was allowed to cool naturally.
The junction of the heat-treated prismatic ceramic _{Thus, Bi 2 Sr 2 CaCu 2 O} x superconductor crystals are produced, where the electrical resistance was measured by a dc four-terminal method, the junction is connected by superconducting crystals The critical temperature at which the electric resistance is zero is about 80 K (Kelvin), and the critical current density at 77 K at zero external magnetic field is about 80 A / cm ^2.
As a result, superconducting properties at substantially the same level as those of the prismatic ceramics before joining were obtained.

In the above description, the Bunsen burner is used as the local heating means. However, the present invention is not limited to the Bunsen burner, and a local heating means such as an oxygen burner, laser heating, or infrared condensing heating can be used.

[0019]

As described above, according to the present invention, Bi ₂ S
Superconducting crystallized glass containing r ₂ CaCu ₂ O _x superconducting crystal
The surface of each joint was heated to a molten state
After that, the joints in the molten state
By heating at a temperature, Bi ₂ Sr ₂ CaCu ₂ O _x
The superconducting crystal is melted and joined, and the superconducting
Time required for conducting crystallized glass at 700 ° C to 880 ° C
Heat in air or an atmosphere containing oxygen,
And let it cool naturally after holding the required time at
Joined without cracks and superconducting at the joint
The characteristics are equivalent to those of the superconducting crystallized glass before joining.
Therefore, a bismuth-based high-temperature superconductor having an arbitrary shape can be joined. Therefore, (1) It is possible to increase the size by joining and combining small high-temperature superconductors. (2) A high-temperature superconductor having a complicated shape can be formed. (3) Since equipment such as a sintering furnace can be downsized,
Significant cost reduction becomes possible. (4) Uniform quality of the high-temperature superconducting product can be maintained. This has the effect.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state before joining of two joined high-temperature superconductors.

FIG. 2 is a perspective view showing a state in which a joint between two high-temperature superconductors to be joined is heated.

FIG. 3 is a perspective view showing a state where a joint portion between two joined high-temperature superconductors is melted.

FIG. 4 is a perspective view showing a state in which a joining portion between two joined high-temperature superconductors is joined.

FIG. 5 is a perspective view showing a state in which the two high-temperature superconductors to be joined are heated after being joined.

FIG. 6 is a perspective view of the joined high-temperature superconductor.

FIG. 7 is a perspective view showing a state before joining of two deformed high-temperature superconductors to be joined.

[Explanation of symbols]

1 superconducting crystallized glass (bonded bismuth-based high-temperature superconductor) 2 Bunsen burner

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Abe 6-1705, Higashiyama, Nisshin-cho, Aichi-gun, Aichi Prefecture (72) Inventor Koichi Nakamura Kanie-cho, Kaifu-gun, Aichi Prefecture 72) Inventor Eikichi Eikichi 5-1-1, Naruko-cho, Midori-ku, Nagoya-shi, Aichi (56) References JP-A-3-877 (JP, A) JP-A-3-242384 (JP, A) 4-321569 (JP, A) JP-A-2-302379 (JP, A)

Claims (1)

(57) [Claims] 1. The method of claim 1 wherein each of Bi, Sr, Ca, and Cu
Heat and melt the mixed oxide material, and cool and solidify it to the required shape
And then heat-treated a plurality of Bi ₂ Sr ₂ CaCu ₂
Connection of superconducting crystallized glass including Ox superconducting crystal
The process of heating the surface of the joint to a molten state
Butted joints that have become molten
At the required temperature
Bi ₂ Sr ₂ CaCu ₂ Ox superconductivity by heating
The step of melting and joining the crystals;
The superconducting crystallized glass in the separated state is heated to 700 ° C. to 880 ° C.
At the temperature of ℃ for the required time in air or atmosphere containing oxygen
After heating at the same temperature and holding for the required time, let it cool naturally
Joining method bismuth-based high temperature superconductor by a process characterized by the this <br/> joining said superconducting crystallized glass.