JPH01298007A - Production of oxide-based superconductor - Google Patents

Abstract

PURPOSE:To obtain the title oxide-based superconductor while remarkably increasing its forming rate in comparison to the conventional method by irradiating the oxide-based superconductor layer being formed on a substrate by plasma spraying with gaseous oxygen plasma to heat-treat the superconductor layer. CONSTITUTION:The molten superconductor powder is discharged from a spray gun 3, for example, and sprayed by the plasma spraying method on a substrate 1 consisting of an elementary metal, an alloy, ceramics, etc., to form a superconductor layer 2. Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O, etc., can be exemplified as the superconductor. The layer 2 being formed on the substrate 1 is irradiated by the oxygen plasma from a gaseous oxygen plasma source 4 under reduced pressure conditions simultaneously with the formation of the superconductor layer 2, and the layer 2 is heat-treated. As a result, the forming rate of the obtained oxide-based superconductor is remarkably increased in comparison to the conventional CVD and PVD, and the productivity is drastically improved.

Description

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

"Prior Art and its Problems" Recently, various oxide-based superconductors have been discovered that exhibit a critical temperature (Tc) higher than the liquid nitrogen temperature when transitioning from a normal conducting state to a superconducting state.

As a method for manufacturing a superconductor made of such an oxide-based superconducting material, for example, a method of forming a superconductor layer on a substrate by a CVD method (chemical vapor deposition method) or a PVD method (physical vapor deposition method) is used. It has been known. However, these CVD methods and PVD methods have a problem in that the layer formation speed is slow and it is not practical to apply them to, for example, the production of cable conductors.

In addition, as a method for producing a superconductor layer at a high speed, a method using plasma spraying may be considered.With this method, the superconductor layer produced does not have a dense structure, for example, Y-B
When manufacturing an a-Cu-0 based oxide superconductor, there is a problem in that an oxygen-deficient perovskite structure having excellent superconducting properties is not sufficiently produced.

"Means for Solving the Problem" Therefore, in the method for manufacturing an oxide-based superconductor described in claim 1 of the present invention, an oxide-based superconductor layer is formed on a substrate by a plasma spraying method, and At the same time, the above problem was solved by heat-treating the superconductor layer being formed on the substrate while irradiating the superconductor layer with oxygen plasma gas.

Further, in the method for manufacturing an oxide superconductor according to claim 2 of the present invention, an oxide superconductor layer is formed on a substrate by a plasma spraying method, and at the same time, an oxide superconductor layer is formed on the substrate. The above problem was solved by heat-treating the superconductor layer while irradiating the conductor layer with oxygen plasma gas through an electron-rich atmosphere.

Hereinafter, an example of the method for producing an oxide-based superconductor according to claim 1 of the present invention will be explained in detail with reference to the drawings.

First, as shown in FIG. 1, prepare the substrate l, and
The superconductor layer 2 is preheated to 400 to 550°C, and then a superconductor layer 2 is deposited on its surface by plasma spraying under reduced pressure.
form. Here, as the substrate 1, a single metal, an alloy,
Ceramic, glass, etc. are used. In addition, a superconductor has the general formula A -B -Cu-0 (where A is Y,
Sc, La, Yb, Er.

Group 111a elements of the periodic table such as Ho, Dy, 13i, S
Group Vb elements of the periodic table such as T1. B represents one or more of the elements of group mb of the periodic table, such as In, and B represents Sr.

Indicates one or more elements of group Ha of the periodic table, such as Ba and Ca. ) refers to an oxide-based superconductor expressed as Specific examples of such superconductors include Y-Ba-Cu-0 series, Bi-5r-Ca-
Cu-0 system, TIB a-Ca-9r-Cu-0 system,
Nd-5r) Ce-Cu-0 system, etc.

The above-mentioned plasma spraying method is a method in which a molten superconductor powder is ejected and sprayed using a spray can 3, for example. This method involves introducing superconductor powder into high-frequency plasma gas using a carrier gas, melting the powder, and spraying it onto the substrate i. Here, oxygen is preferably used as the carrier gas, but other inert gases such as argon and nitrogen can also be used. In addition, as a method for producing the above-mentioned superconductor powder, for example, when producing a Y-Ba-Cu-0 based superconductor, Y,03 powder, Ba-CO3 powder, and CuO powder are mixed into Y:Ba:Cu powder. =l:2:
Y+BapCUs-Ox
(However, x = 7 - δ, 0≦δ≦5) How to obtain superconducting powder expressed by the composition ratio, and A in the above general formula.
, B, and C elements are used as a gas phase source, and the organic compounds in the gas phase source are instantaneously decomposed by high heat in a desired ratio to burn out the organic substances in the gas phase source, and the A, B, and B elements in the material are , excite C element in high heat and gasify it,
Further, methods such as sublimation, heating and pulverization to produce superconducting powder are adopted.

Furthermore, the pressure reduction condition during the above treatment was 100T.
orr or less is preferable, and an oxygen atmosphere is preferable as the reduced pressure atmosphere.

Further, at the same time as forming such a superconductor layer 2, the substrate 1 is
The superconductor layer 2 being formed thereon is irradiated with oxygen plasma gas from the oxygen plasma gas supply source 4 under reduced pressure, and the superconductor layer 2 is subjected to heat 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 Fig. 2, a vacuum is maintained between the cathode 5 and the anode 6, and a DC voltage is applied between them to cause arc discharge. Oxygen is vented through the oxygen tube 7, and the oxygen is heat-exchanged with the arc to form plasma, which is then heated under reduced pressure to the substrate 1 described above. This is a method of irradiating the superconductor layer 2.

As shown in FIG. 3, the method using high-frequency plasma involves keeping the inside of the quartz tube 8 under reduced pressure and aerating oxygen into the quartz tube 8, and then installing a high-frequency coil 9 (not shown) wound around the quartz tube 8 in parentheses. In this method, a high-frequency power source is connected, oxygen in the quartz tube 8 is turned into plasma by high-frequency electromagnetic induction, and the plasma is irradiated onto the superconductor layer 2 of the substrate 1 described above under reduced pressure.

Furthermore, the heating temperature for the heat treatment of the superconductor layer 2, which is carried out simultaneously with such oxygen plasma gas irradiation treatment, is 20
The cropping rate is 0 to 150°C, and the treatment time for oxygen plasma gas irradiation and heating 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 this method of manufacturing an oxide-based superconductor, the superconductor layer 2 is formed by plasma spraying, so the production speed is much faster than that of conventional CVD or PVD methods, and production is much faster. Improves sex.

Furthermore, since the superconductor layer 2 is irradiated with plasma-excited oxygen by irradiating the oxygen plasma gas at the same time as the formation of the superconductor layer 2, oxygen is sufficiently supplied into the superconductor layer 2, thereby increasing the superconductivity. When the body layer 2 is heat-treated, it becomes a superconductor with an oxygen-deficient perovskite structure, and since enough oxygen is taken into the crystal, oxygen is extracted from the crystal and the crystal structure changes. ,
Inconveniences such as deterioration of superconducting properties are prevented.

Furthermore, since the heat treatment is performed while irradiating oxygen plasma gas at the same time as the formation of the superconductor layer 2, the formation of the superconductor layer 2 and its annealing treatment are performed at the same time, which improves productivity and improves the conditions for the annealing treatment. is lower and takes a shorter time than before.

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

Next, the difference between the manufacturing method described in claim 2, which is characterized by the manufacturing method of an oxide-based superconductor according to claim 2 of the present invention, from the manufacturing method described in claim 1 is that When a certain superconductor layer 2 is irradiated with oxygen plasma gas, the oxygen plasma gas is passed through an electron-rich atmosphere and irradiated with the oxygen plasma gas.

Simultaneously with the formation of the superconductor layer 2 by the plasma spraying method, the superconductor layer 2 being formed on the substrate I'2 is irradiated with oxygen plasma gas from the oxygen plasma gas supply source 4 under reduced pressure and subjected to heat treatment. At this time, the oxygen plasma gas is passed through an electron-rich atmosphere E shown by the dashed line in FIG. Here, to create an electron-rich atmosphere E,
For example, as shown in FIG.
By causing the electrons to travel toward the anode 12, an electron shower 13 with an electric atmosphere is formed. Then, the above oxygen plasma gas is passed through the electron shower 13 and is irradiated onto the temporary superconductor layer 2 while avoiding the passage of the oxygen plasma gas. The molecules are ionized and collide with the superconductor layer 2. In the example shown in FIG. 4, the method of generating the electron shower 13 is to emit thermoelectrons, but other methods such as emitting photoelectrons may be adopted.

According to such a manufacturing method, Electron Noah 1
3, the oxygen ions are ionized and excited and collide with the superconductor layer 2, so that the individual atoms in the irradiated oxygen plasma gas participate in the reaction with the superconductor layer 2, forming crystals. Therefore, the superconductor layer 2 becomes a superconductor having an oxygen-deficient perovskite structure by being heat-treated.

In addition, by passing through the electron shower 13 and irradiating oxygen plasma, the reaction and bonding between the superconductor layer 2 and the excited oxygen ions is greatly promoted, so the heat treatment conditions are lower and lower than in the past. It will be a short time.

In the above example, these thin film layers formed on a substrate were used as superconductors, and heat treatment was performed while irradiating oxygen plasma gas. Alternatively, a thin film layer formed on the surface of a tape-shaped Jλ body may be used.Furthermore, the metal coating layer may be removed from a superconducting wire having a metal coating layer, and a core wire made of the exposed superconductor may be used. It's good.

"Effects of the Invention" As explained above, the method for producing an oxide-based superconductor according to claim I of the present invention forms an oxide-based superconductor layer on a substrate by a plasma spraying method, and At the same time, since the superconductor layer being formed on the substrate is heat-treated while irradiating the superconductor layer with oxygen plasma gas, the superconductor layer is formed by a plasma spraying method, which is different from conventional CVD. The production speed is much faster than that of the PVD method or the PVD method, and productivity is significantly improved.

In addition, oxygen can be sufficiently supplied into the superconductor layer,
Therefore, the superconductor layer can be an oxide-based superconductor having a structure with sufficient oxygen in its crystals, and the obtained oxide-based superconductor has excellent superconducting properties such as a high critical temperature. becomes.

Furthermore, 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, thereby improving productivity. be able to.

Further, the method for producing an oxide superconductor according to claim 2 of the present invention includes forming an oxide superconductor layer on a substrate by a plasma spraying method, and at the same time forming an oxide superconductor layer on the substrate. Since the superconductor layer is heat-treated while being irradiated with oxygen plasma gas through an electron-rich atmosphere, the oxygen ions that are ionized and excited by passing through the electron-rich atmosphere are The oxygen ions collide with the superconductor layer and are incorporated into the crystals of the superconductor layer, thus making the superconductor layer or an oxide-based superconductor having a structure with sufficient oxygen in its crystals, and thus the obtained oxide. The system superconductor has strong superconducting properties such as a high critical temperature.

In addition, by passing through an electron-rich atmosphere and irradiating oxygen plasma, the reaction and bonding between the superconductor layer and excited oxygen ions is greatly promoted, so the heat treatment conditions are lower and shorter than conventional ones. Therefore, it is possible to improve productivity.

[Brief explanation of the drawing]

1 to 4 are diagrams related to the present invention, in which FIG. 1 is a schematic configuration diagram for explaining an example of the manufacturing method of the present invention, and FIG. 2 is a diagram showing an oxygen plasma gas using DC arc discharge. FIG. 3 is a schematic configuration diagram for explaining a processing method for generating oxygen plasma gas using high frequency plasma, and FIG. 4 is a schematic configuration diagram for explaining a processing method for generating oxygen plasma gas using high frequency plasma. FIG. 2 is a schematic configuration diagram for explaining a manufacturing method. 1...Substrate, 2...Superconductor layer, 3.
...Thermal spray gun, 4...Oxygen plasma gas supply source, 13...
...Electron Shower E...Electron-rich atmosphere.

Claims (2)

[Claims] (1) An oxide-based superconductor layer is formed on a substrate by plasma spraying, and at the same time, the superconductor layer being formed on the substrate is irradiated with oxygen plasma gas. A method for producing an oxide-based superconductor, the method comprising heat treatment. (2) An oxide-based superconductor layer is formed on the substrate by plasma spraying, and at the same time, oxygen plasma gas is irradiated to the superconductor layer being formed on the substrate through an electron-rich atmosphere. A method for producing an oxide-based superconductor, comprising heat-treating the superconductor layer while