JPH083968B2 - How to make a superconductor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a thin film ceramic-based superconducting (also called superconducting) material. The present invention is intended to produce an electronic device or device using superconductivity by selectively irradiating a material formed by thinning a substrate with laser light.

"Background of the Invention" Conventionally, superconducting materials metallic material Nb-Ge (e.g. Nb ₃ Ge) is used. Since this material is a metal, it has high ductility and malleability, and it was possible to perform coil winding for a superconducting magnet.

However, superconducting materials using these metallic materials are
(The superconducting critical temperature is hereinafter simply referred to as Tc) is as small as 23K or less. On the other hand, if industrial application is considered, it is more effective if this Tc is 77K, preferably room temperature or higher.

“Conventional Problems” For this reason, ceramic-based materials, particularly oxide ceramic-based materials, are attracting attention as materials with high Tc, rather than metals. However, despite the high Tc of the ceramic-based superconducting material, which has been attracting attention, it is poor in bendability, ductility, and malleability, and is slightly bent. Iwanya 0.1-30μ
It has been considered impossible to form a thin film having a thickness of m on a substrate and selectively remove a part or all of this thin film. In particular, this is used for multi-layer wiring using the same photolithography technology as semiconductor integrated circuits,
It was completely impossible to make a new electron device using this thin film superconductivity.

"Means for Solving the Problem" The present invention is such a thin film, and an electronic device is manufactured using the thin film.

According to the present invention, a substrate having a desired shape, for example, a cylindrical or plate-shaped substrate is preliminarily made into a thin film ceramic material, particularly an oxide ceramic material or a starting material which becomes a superconducting oxide ceramic after annealing in an oxidizing atmosphere. It is formed by a beam evaporation method, a sputtering method, a printing method such as a screen printing method, or another method.

When this thin film is formed, the thin film initially exhibits an amorphous structure or a polycrystalline structure having fine crystals having a large amount of lattice strain and lattice defects. This structure is generally conductive or insulating without semiconductor or superconductivity.

Therefore, the film in such a state is subjected to thermal oxidation or firing at 930 to 950 ° C., and then gradually cooled to be transformed into a superconducting material having an orthorhombic pervskite structure. The present invention, when the superconducting ceramics is heated to a high temperature of 1000 ° C. or higher by laser light or strong light similar thereto, and rapidly cooled, the irradiated region is transformed into a tetragonal perovskite structure or an amorphous structure, and becomes a non-superconducting material. I discovered it experimentally. Therefore, in the present invention, after firing such ceramics into a superconducting material, laser light is selectively irradiated, and scanning is further performed as necessary to form a certain region, for example, a band having a certain width. Transform the ceramic material into a non-superconducting material.

Then, this laser irradiation transforms into a polycrystalline or amorphous structure having a tetragonal crystal structure, and a superconducting material having a constant Tc only in a portion other than this region can be obtained. The film formed by this sputtering method adjusts the target, and uses a ceramic superconducting material such as (A _1-X Bx) yC.
uzOwXv However, x = 0.1-1, preferably 0.6-0.7, y = 2.0-4.
0 preferably 2.5 to 3.5, z = 1.0 to 4.0, preferably 1.5 to 3.5,
w = 4.0 to 10.0, preferably 6 to 8, v = 0 to 3.0, and A
Is one or more elements selected from Group IIIa of the periodic table of elements, especially yttrium (Y) or lanthanoids, B
Is one or more kinds of elements selected from the group IIa of the periodic table of elements, for example, barium (Ba). X is an element selected from Group VIIa or VIIb of the periodic table of elements, and the former representative example is manganese (Mn). A typical example of the latter is fluorine (F) or chlorine (Cl).

The laser light source of the present invention is, for example, a YAG laser (wavelength 1.06 μm).
m), an excimer laser (KrF, KrCl, etc.), a carbon dioxide laser or a nitrogen laser was used. The YAG laser can repeatedly irradiate a circular laser beam at a frequency of 0.5 to 100 KHz, and only the irradiated part can raise the temperature of the ceramics and rapidly cool it. Since this ceramic has a relatively small thermal conductivity coefficient and becomes a polycrystal having an amorphous or tetragonal perovskite structure by rapid cooling, it is possible to selectively make only the portion irradiated with laser light a non-superconducting material. it can.

When using an excimer laser, a rectangular surface such as 20
It is possible to perform pulse irradiation on × 30 mm ² .
In the present invention, a circle (diameter 10 to
A laser beam in a band shape (width 5 to 100 μm, length 10 to 40 cm) can be produced, and the substrate or the laser light beam is moved while irradiating the ceramic film with the laser beam. At this time, the ceramics in the desired irradiation region can be made a non-superconducting material.

The present invention thus selectively irradiates the ceramic material formed on the surface of the substrate with laser light and, if necessary, scans the portion to transform the oxide superconducting material into a non-superconducting material. It is characterized by that. Then, the region of the peripheral portion which is not irradiated with the laser light can substantially remain as the superconducting ceramics.

In the present invention, alumina, YSZ (yttria stabilized zircon), silicon nitride, aluminum nitride, zirconia, yttria, and strontium titanate were used as the substrate material. A metal such as copper or a copper alloy may be used. However, Tc in the region where YSZ and strontium titanate, which have the most similar thermal expansion coefficient, are not irradiated with laser.
Could get high.

[Operation] When a conventional metal superconducting material is used, a wire is first used as the process. This was applied to a predetermined substrate to form a coil.

However, with regard to the ceramic superconductor of the present invention, a base body of the final shape is provided, and after the crystallization heat treatment on this base body,
A material having an orthorhombic perovskite structure and having superconducting properties is formed into a film (which does not exhibit superconductivity as it is). Then, after heat-treating this film to form a superconducting ceramics on the entire surface, the film is selectively irradiated with laser and rapidly cooled (quenched) to form a tetragonal or amorphous structure only in the irradiated part. By arbitrarily scanning this laser beam, it is possible to derive an area having a non-superconducting property of an arbitrary line, band, or surface only in the surface area. Then, only the ceramics other than this irradiation region are made to have ceramics having superconducting properties, and at a temperature of Tco (temperature at which electric resistance becomes zero) or lower, the resistance can be "0" or a state close thereto.

 The present invention will be described below with reference to examples.

Example 1 FIG. 1 shows an example of the present invention.

In FIG. 1, the substrate (1) is a ceramic material such as YS.
Z was used. A metal may be used. In these cases, it is preferable that the difference in coefficient of thermal expansion is similar to that of the ceramic film (within ± 50%). If this difference is too large, the superconducting ceramic thin film (2) made in advance has stress strain, the temperature at which superconductivity is exhibited is small, and the superconductivity is not observed due to cracks in the film. In this embodiment, 0.1 to 50 μm is formed on a substrate having a plate-like shape by an electron beam evaporation method, a sputtering method or a printing method such as a screen printing method.
For example, the ceramic (2) was formed to a thickness of 20 μm.

The material is (A _1-X Bx) yCuzOwXv, x = 0.67,
y = 3, z = 3, w = 6-8, v = 0-3, and A as Y, B
As Ba and X as Mn.

It was heat-treated in an oxidizing atmosphere. 500-1000
It was carried out at 15 ° C. for 15 hours. Thus, a superconducting ceramic film was formed. Furthermore, here the YAG laser (wavelength
1.06 μm) (4) was irradiated for laser treatment.
The substrate was kept at room temperature with this laser light and scanned from the left end to the right end in FIG. 1 to form a region (3). The peak output of YAG laser light (4) was 10 ⁶ to 10 ⁷ W / sec. Therefore, this region (3) was once melted and then rapidly cooled to become a polycrystalline body having a partially amorphous and partially tetragonal perovskite structure, and a non-superconducting region could be formed. If this is made too strong, the substrate (1) will also be damaged, so care must be taken.

It is also possible to perform this laser light using an excimer laser. In this case, excimer laser light (wavelength 0.25μ
m) and continuously scan while irradiating. Since this is a pulsed light, 80-98% of the next rectangular beam overlaps one rectangular spot so that the pulse scans over the band. That is, the scanning speed of the laser light was 2 cm / min, the frequency was 10 KHz, and the beam diameter was 50 μm × 10 cm.

Embodiment 2 FIG. 2 shows another embodiment of the present invention.

In the drawing, the base (1) has a cylindrical shape. The film-shaped ceramic material (2) is formed here as in the first embodiment.

This production is performed by using a printing device to move the cylindrical substrate (1) to the arrow (1
Coating may be performed while rotating as shown in 2).

Next, after drying these films, they were heat-treated in oxygen at 950 ° C. for 15 hours. And all of this thin film was transformed into a superconducting material. When this superconducting material was examined with an X-ray analyzer, it was found to have polycrystals with an orthorhombic pervskite structure.

Next, while irradiating this film with a YAG laser (4) beam (diameter 50 μm) at room temperature, this laser light is gradually moved in the direction (11). At the same time, the cylinder (1) is rotated in the direction of the arrow (12). Then, one continuous strip-shaped irradiation region (3) can be formed on this cylindrical substrate. When this was examined by an X-ray analyzer, microcrystals having a perovskite structure having a tetragonal crystal form and amorphous structures were mixed. And it was electrically semi-insulating with non-superconducting properties. The ceramics (5-1) and (5-2) having respective superconducting properties can be electrically separated by this region to form a superconducting region. Here, the superconducting region had a coil shape, and could substantially constitute a superconducting magnet coil.

In the present invention, in order to rapidly cool the area irradiated with laser light, the atmosphere during this irradiation is kept at 100 ° C. or lower, preferably room temperature, and the pulsed light is scanned at a laser speed of 20% or less so that they overlap each other. Was used faster.

 Thus we were able to make a superconducting magnet.

By connecting the start point and the end point of this coil with a superconducting wire, an energy storage device can be obtained.

 Others are the same as the first embodiment.

"Effect" The present invention makes it possible to selectively leave a ceramic superconductor, which has heretofore been impossible at all, in a substantially coil shape or another shape on a substrate.

In the present invention, laser light is used as the energy source. However, this portion may be irradiated with electron beam light. However, in such a case, since the surface to be irradiated is held in vacuum, there is a drawback that it is difficult to cool rapidly.

Thus, a ceramic superconducting material that would be easily broken when bent could be formed into a film or a wire as an isolation for forming a conductor, an electrode or a superconducting element.

In the present invention, it is important to consider the industrial stress of forming a superconducting film and then performing a predetermined patterning using a known photolithography technique to obtain a superconducting element or a superconducting wiring.

The superconducting material of the present invention may be any ceramic material.

[Brief description of drawings]

1 and 2 show examples of the superconducting ceramics of the present invention. 1 ... Substrate 2 ... Superconducting ceramic material 3 ... Region not exhibiting superconductivity 4 ... Laser light 5 ... Region exhibiting superconductivity

Claims (3)

[Claims] 1. A step of forming a superconducting material exhibiting a superconducting state on a substrate, and a predetermined region of the material is selectively irradiated with a laser beam or intense light equivalent thereto to quench the material to rapidly cool the non-superconducting material. A method for producing a superconductor, characterized by: 2. A method for producing a superconductor according to claim 1, wherein the superconducting material has an orthorhombic pervskite structure and a predetermined region has a tetragonal pervskite structure or an amorphous structure. Method. 3. A method for producing a superconductor according to claim 1, wherein a substrate having a coefficient of thermal expansion substantially within ± 50% of a coefficient of thermal expansion of the ceramic material is used.