JPH01298006A - Production of oxide-based superconductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION 1-Field of Industrial Application The present invention relates to a method for manufacturing a superconductor used as a superconducting circuit material such as a Noyosefson element or a superconducting material for various superconducting devices.

"Conventional technology" Critical 7EF that has recently transitioned from a normal conducting state to a superconducting state
Oxide-based superconductors whose n degrees (Tc) is higher than the temperature of liquid nitrogen have been discovered.

As a method for manufacturing a superconductor made of such an oxide-based superconducting material, for example, a superconductor is deposited on a substrate by a CVD method (chemical vapor deposition method) or a VD method (physical vapor deposition method). Methods of forming layers or superconducting precursor layers are known.

By the way, in such a method, after forming a superconductor layer or a superconducting precursor layer on a substrate, the entire substrate is heated at about 500 to 900°C for about 5 to 24 hours to form the superconductor layer or superconducting precursor. It is common to anneal the layers to form a superconductor with good superconducting properties.

"Problem to be solved by the invention" However, in the above method, the annealing time is 5 degrees.
Since the temperature is as high as 00 to 900°C, there are disadvantages such as the inability to use materials with a low melting point as the substrate material, and the annealing time also takes about 5 to 24 hours, resulting in a problem that production efficiency is impaired.

Furthermore, when manufacturing an oxide-based superconductor such as Y-B a-Cu-0, it is desirable to fabricate an oxygen-deficient perovskite structure with excellent superconducting properties; When manufacturing a physical superconductor, heat treatment is performed in an oxygen atmosphere with as high a concentration as possible so that oxygen atoms are fully incorporated into the crystal, and at a temperature that prevents oxygen atoms from escaping to the outside of the crystal. It is considered important to do so. However, in order to perform the heat treatment under such temperature conditions that prevent oxygen atoms from escaping to the outside of the crystal, it is necessary to heat the material at a higher temperature and for a longer period of time, which aggravates the above-mentioned disadvantages.

The present invention was made in view of the above circumstances, and its purpose is to provide a method for manufacturing a superconductor that allows a wide selection of substrate materials, simplifies the annealing process, and has excellent superconducting properties. It's about doing.

"Means for Solving the Problems" In the method for producing an oxide-based superconductor of the present invention, when heat treating a superconductor or superconducting precursor, the superconductor or superconducting precursor is heat-treated while being irradiated with oxygen plasma gas. was used as a means of solving the above problem.

Hereinafter, an example of the method for manufacturing an oxide-based superconductor of the present invention will be explained in detail with reference to the drawings.

First, a substrate is prepared on the surface of which a layer made of a superconductor or a superconducting precursor is formed. Here, as the substrate, single metals, alloys, ceramics, etc. are used, but low melting point metals and alloys with a melting point of about 450°C or higher can also be used, and furthermore, they have heat resistance that does not cause degeneration etc. up to about 450°C. Materials such as synthetic resins with excellent properties can be used. In addition, a superconductor has the general formula A-B-Cu-0 (where A is Y).

Periodic table f for Sc, La, Yb, Er, Ho, Dy, etc.
F1A group elements, elements of Group VB of the periodic table such as Bi and Sb, and elements of Group MB of the periodic table such as Tljn, and B represents one or more elements of Group 1 Ta of the periodic table such as Sr, Ba, Ca, etc. Indicates one or more elements. ), and a superconducting precursor is an intermediate between the oxide superconductor and a superconductor material.

In addition, specific examples of such superconductors include Y-Ba-Cu-0 system, B i-9r-Ca
-Cu-0 series, TiBa-Ca-9r-Cu-0 series, Nd-9r-Ce-Cu-0 series, etc.

In addition, in order to produce such a superconductor, for example, organic compounds containing A, B, and Cu elements in the above general formula are used as gas phase sources, and these are instantaneously pyrolyzed with high heat to decompose the organic compounds in the gas phase source. A, B, C in the material by burning off organic matter
CVD, in which the u element is excited in high heat, gasified, and then sublimated and deposited on the substrate in the form of ultrafine powder, thereby forming a thin film superconducting layer or superconducting precursor layer.
method (chemical vapor deposition method) or the bulk of an oxide-based superconductor with the same or similar composition to the thin film layer to be formed, and irradiates this target with a laser beam to evaporate a portion of it. A PVD method (physical vapor deposition method), which forms a superconductor layer or a superconductor precursor layer by vapor deposition on a substrate, is preferably employed.

Next, the superconductor layer or superconductor precursor layer of the prepared substrate is heat-treated while irradiating oxygen plasma gas to perform an annealing treatment. In this case, as a method for producing oxygen plasma gas, a method using direct current arc discharge, a method using high frequency plasma, etc. are adopted.

In the method using DC arc discharge, as shown in Figure 1, a vacuum is maintained between cathode 1 and anode 2, and a DC voltage is applied between them to cause arc discharge, and oxygen is supplied to the discharge point A. This is a method in which oxygen is vented through the tube 3, the oxygen is heat-exchanged with the arc, turned into plasma, and the superconductor layer 5 or superconductor precursor layer (5) of the substrate 4 described above is irradiated with this under reduced pressure. .

In the method using high-frequency plasma, as shown in FIG. 2, the inside of the quartz tube 6 is kept under reduced pressure, and the quartz tube 6. A high frequency coil 7 is wound around the quartz tube 6 and has oxygen vented therein.
A method of connecting a high-frequency power supply as shown in the diagram to a high-frequency electromagnetic induction to turn the oxygen in the quartz tube 6 into a plasma state, and irradiating this onto the superconductor layer 5 or superconductor precursor layer (5) of the substrate 4 described above under reduced pressure. It is.

In addition, the heating temperature in the heat treatment of the superconductor layer 5 or the superconducting metamorphic layer (5), which is performed simultaneously with the oxygen plasma gas irradiation treatment, is approximately 200 to 450°C, and the oxygen plasma gas irradiation and The heating treatment time is about 2 to 5 hours. Further, as a heating method, in addition to heat treatment in a heating furnace, heat radiation heating method from the outside using a heater or the like can be adopted.

According to such annealing treatment, oxygen excited in a plasma state forms the superconductor layer 5 or the superconductor precursor layer (5).
Since the superconductor layer 5 or the superconducting precursor layer (5) is irradiated with oxygen, sufficient oxygen is supplied to the superconductor layer 5 or the superconductor precursor layer (5).
Alternatively, the superconducting precursor layer (5) becomes a superconductor having an oxygen-deficient perovskite+ structure by being heat-treated, and since sufficient oxygen is incorporated into the crystal, oxygen is extracted from the crystal. Disadvantages such as changes in crystal structure and deterioration of superconducting properties are prevented, and for example, compared to the critical temperature of about 85 to 94 degrees in the conventional method, the critical temperature in the method of the present invention is about 93 degrees to 96 degrees. It becomes an oxide-based superconductor with good superconducting properties.

Furthermore, since excited oxygen is supplied sufficiently by irradiating the oxygen plasma, the heat treatment conditions are lower and shorter than those of the conventional method.

Furthermore, by generating and irradiating oxygen plasma gas under reduced pressure, the production rate of oxygen plasma and oxygen ions is accelerated, and their flight speed is increased, so there is a higher probability that they will be incorporated into the superconductor crystal. Therefore, a sufficient amount of oxygen can be supplied in a short time.

In the above example, these thin film layers formed on a substrate as superconductors or superconducting precursors were used and heat treated while irradiating oxygen plasma gas. It may be formed into a desired shape such as a shape, or it may be formed as a thin film layer on the surface of a tape-like base.
Furthermore, the metal coating layer may be removed from a superconducting wire having a metal coating layer, and a core wire made of an exposed superconductor or superconducting precursor may be used.

"Effects of the Invention" As explained above, the method for producing an oxide-based superconductor of the present invention performs heat treatment by heating the superconductor or superconducting precursor while irradiating it with oxygen plasma gas. Oxygen can be sufficiently supplied into the superconductor or superconducting precursor, and the superconductor or superconducting precursor can be made into an oxide-based superconductor having a structure with sufficient oxygen in its crystals. The resulting oxide-based superconductor has excellent superconducting properties such as a high critical temperature.

In addition, by irradiating oxygen plasma gas, excited oxygen can be sufficiently supplied into the crystal, so the heat treatment conditions can be lowered and shortened compared to conventional methods.
Therefore, productivity can be improved.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams related to the present invention, with Figure 1 being a schematic configuration diagram for explaining the method using DC arc discharge, and Figure 2 being a schematic configuration diagram for explaining the method using high-frequency plasma. It is a schematic configuration diagram. 1... cathode, 2... anode, 4...
. . . Substrate, 5 . . . Superconductor layer or superconducting precursor layer, 7 . . . High frequency coil.

Claims (1)

[Claims] When heat treating superconductors or superconducting precursors,
A method for producing an oxide-based superconductor, which comprises heat-treating a superconductor or a superconducting precursor while irradiating the superconductor or a superconducting precursor with oxygen plasma gas.