JPH02257528A - Manufacture of oxide superconductor - Google Patents

Abstract

PURPOSE:To enhance the critical current density of an oxide superconductor by attaching and solidifying an oxide superconducting material on the outside of a metal core wire covered with silver, and irradiating it with laser beam. CONSTITUTION:A Y-Ba-Cu-O type oxide is contained in a melting pot 2 and is melted by a heater 7. A silver-plated copper wire 1 cooled is provided which passes through the oxide from die 9, and a molten body is blown out to the outer periphery of the wire and is cooled by gas and irradiated with laser beam 6. A solidified layer is thus immediately melted and solidified by the laser beam in a narrow band. The silver plating layer reflecting the laser beam serves as a buffer layer for preventing reaction of the metal core wire with the oxide, and the metal core wire absorbs energy of the laser beam, and thereby crystal is grown in the cross direction of the wire so that orientation of the wire in axial direction is prevented from deteriorating.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for producing an oxide superconductor, and in particular to a method for producing an oxide superconductor, in particular a linear oxide superconductor that has excellent crystal orientation, that is, superconducting properties, and electrical and mechanical stability. The present invention relates to a method for producing an oxide superconductor.

[Prior Art] In recent years, the development of oxide superconducting materials has progressed at a remarkable speed, and the use of superconducting materials such as La-based, Y-based, old yarn, and TI-based materials is considered to be promising.

However, these materials have anisotropy in their superconducting properties, that is, there are significant differences in properties depending on the crystal orientation, and simply molding and sintering the raw material powder obtained by normal synthesis methods only yields materials with random crystal orientation. Therefore, there is a problem in that electrical and magnetic properties that reach a practical level cannot be obtained.

As a method to solve the above problem, an attempt has been made to increase crystal orientation by melting an oxide superconducting material and moving this melt relatively in an electric furnace with a temperature gradient to grow crystals. ing.

Furthermore, attempts have been made to improve crystal orientation by forming a floating zone in a superconductor, such as a linear superconductor, and melting and solidifying the superconductor.

[Problem to be solved by the invention] However, in the former melting temperature gradient crystallization method, there is a limit to the setting of the temperature gradient, and it is impossible to form a large gradient in the furnace by heat conduction, so it is difficult to change the crystal orientation. A disadvantage is that it is difficult to control.

On the other hand, the latter method using a floating zone has the disadvantage that only a phase that stably crystallizes from the liquid phase can be obtained, and that the growth rate thereof is extremely slow, ranging from several marks to several mm/hr. In particular, in this method, Y-Da-Cu
In the case of -0-based oxide, a fatal drawback is that the insulating material Y2BaCu0x phase is produced by melting and recrystallization, but the superconducting material YBa2 Cu30X phase is not produced.

Further, in any of the above methods, there is also a problem that it is necessary to integrate 11i with a stabilizing material or a mechanical reinforcing member when forming the wire into a wire. In this case, it is possible to use metal wire as a reinforcing material and a stabilizing material, but a diffusion reaction with the metal wire occurs during heat treatment during crystallization of the oxide.
It has the disadvantage that superconducting properties deteriorate.

The present invention has been made to solve the above-mentioned difficulties.
The object of the present invention is to provide a method for producing a linear oxide superconductor having excellent crystal orientation, that is, superconducting properties, electrical stability, and mechanical strength using a laser beam.

[Means for Solving the Problems] In order to achieve the above object, the method for producing an oxide superconductor of the present invention provides a method for producing an oxide superconductor in which a molten oxide superconducting material or an oxide After a raw material containing elements constituting a superconducting material is adhered and solidified to form a solidified layer, the solidified layer is irradiated with a laser beam, and the molten zone formed by this irradiation is rapidly moved. It is.

The oxide superconducting material in the present invention is not particularly limited, and includes, for example, La-Ba-Cu-0, La-8r-C
a-Cu-0 series, Y-Ba-Cu-0 series, old-3r-C
Examples include a-Cu-0 type oxides, Tl-Ba-Ca-Cu-0 type oxides, and the like.

In addition, as the raw material containing the elements constituting the oxide superconducting material, oxides, carbonates, nitrates, metal soaps, etc. containing these elements are used; for example, Y-Ba-
In the case of Cu-0, Y2O6, BaC03, and CuO are used.

The metal core wire in the present invention may be made of copper, stainless steel, titanium, etc., as long as it does not dissolve during the formation of the solidified layer, and the silver coating may be applied by plating, steaming blue, or the like.

Further, the laser beam in the present invention is Ar1YAG5
A CW (continuous) laser such as CO2 is used to irradiate multiple lasers so that a symmetrical temperature distribution is formed in a cross section perpendicular to the axial direction of the wire, especially in which a solidified layer is formed on the outside of the silver coating layer. It is also preferable to irradiate the beams so that the beam diameters overlap each other.

For this reason, a wire having a circular cross section is irradiated with multiple laser beams at equal angles toward the center of the wire so as to form a concentric solid temperature distribution. For example, a laser beam with a beam diameter of about 20 μmφ is used to form a melting zone with a length of about 50 μm, and the wire (or beam) is
Move at a speed of about e.

The power of the laser beam is adjusted to a level that completely melts the solidified layer.

[Operation] In the present invention, since the solidified layer is rapidly melted and solidified in a very narrow band by a laser beam, it is possible to achieve a very large temperature gradient, which allows crystals with very high orientation to be formed. can be obtained, and a wire with excellent superconducting properties can be obtained. Furthermore, since the silver coating layer reflects the laser beam, it acts as a buffer layer to prevent the reaction between the metal core wire and the oxide, and the metal core wire absorbs the energy of the laser beam, causing crystals to grow in the cross-sectional direction. This prevents deterioration of axial orientation. Furthermore, since the metal core wire serves as a stabilizing material and a reinforcing material, it is possible to manufacture a long wire material with excellent electrical and mechanical stability.

Note that silver is known to have no adverse effect on the superconducting properties of oxide superconducting materials.

[Example] FIG. 1 is a schematic diagram showing an example of an apparatus used in the method of the present invention. In the figure, 1 is a silver-plated copper wire with an outer diameter of 20 μmφ, 2 is a melting crucible, 3 is a molten oxide, 4 is an upper cooler, 5 is a lower cooler, and 6 is a laser beam.

Y-Ba-Cu-0 based oxide (
Y:Ba:Cu -1:2:3), and the heater 7
The inside of the crucible was heated to 1200° C. or higher to melt the oxide 3. The liquid surface 3' of this melt is pressurized by gas 8, and a silver-plated copper wire 1 cooled by an upper cooler 4 is passed through a die 9 at the bottom of the crucible, and about 10
After ejecting at a rate of cfll/see and immediately cooling with gas in the lower cooler 5, a laser beam 6 was irradiated from the outer periphery. The laser beam has an output of 50 hW and a beam diameter of 20 μl.
Using 30 wires with diameters of φ, irradiation was performed at equal angles from the outer periphery of a wire 10 with an outer diameter of 100 μιφ.

FIG. 2 shows the superconducting wire 11 obtained in this way, in which a silver plating layer 13 is applied to the outer periphery of the copper wire 12. An oxide layer 14 crystallized on the outside of the silver-plated copper wire 1 It has a structure in which

The axial crystal orientation, critical current density (external magnetic field OT, 77K), etc. of the superconducting wire thus obtained are shown in the table below.

As a comparative example, a copper wire with the same diameter as in the example was used, and the other parts were manufactured in the same manner as in the example.Superconducting wire*: No orientation in the layer adjacent to the surface of the copper wire [Effects of the invention] As stated above. In addition, according to the method for producing an oxide superconductor of the present invention, a superconductor having a high crystal orientation and a high critical current density can be easily obtained, and it is also easy to control the superconductor. It is possible to produce superconductors with excellent physical and mechanical stability at high speed, and its value as a practical method is extremely high.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the apparatus used in the method of the present invention, and FIG. 2 is a sectional view of a superconducting wire manufactured by the apparatus of FIG. 1. 1・・・・・・・・・Silver plated copper wire 2・・・・・・
...Melting crucible 3...Melted oxide 4.5...Cooler 6...Laser beam

Claims (2)

[Claims] (1) After forming a solidified layer by adhering and solidifying a melted oxide superconducting material or a raw material containing an element constituting the oxide superconducting material on the outside of a metal core wire whose outer periphery is coated with silver, the solidified layer is A method for producing an oxide superconductor, which comprises irradiating a laser beam onto the oxide superconductor and rapidly moving a molten zone formed by the irradiation. (2) The method for manufacturing an oxide superconductor according to claim 1, wherein a plurality of laser beams are irradiated.