JPH0531495B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a superconducting material in which a film made of a superconducting substance is formed on the surface of a base material. [Prior Art] Superconducting materials have already been put to practical use in the form of superconducting magnets in high-energy particle accelerators, MRI-CT for medical diagnosis, and physical property research equipment. Such superconducting materials have a wide range of applications, such as power generators, energy storage and conversion,
Linear motor cars, magnetic separation equipment for resource recovery,
Applications of superconducting materials to nuclear fusion reactors, power transmission cables, magnetic shielding materials, etc. are expected, and superconducting materials using the Josephson effect are also expected to be used in ultra-high-speed computers, infrared detectors, and low-noise amplifiers and mixers. Applications of the device are expected. The magnitude of the industrial and social impact when these are fully put into practical use is immeasurable. A typical superconducting material developed so far is Nb-Ti alloy, which is currently widely used as a wire for generating magnetic fields up to 9T.
The Tc (critical temperature at which a superconducting state exists) of the Nb-Ti alloy is 9K. Compound-based superconducting materials have been developed as superconducting materials with Tc much higher than this Nb-Ti alloy, and currently Nb ₃ Sn (Tc: 18K) and V ₃ Ga
(Tc: 15K) has been made into wire rod and is in practical use. Furthermore, according to Nb ₃ Ge, a Tc of 23K has been obtained. As described above, efforts have been made for many years to obtain superconducting materials with high Tc, but Tc23K is currently a major barrier to conventional alloy-based and compound-based superconducting materials. That is,
Cooling superconducting materials with Tc below 23K requires expensive liquid helium, which hinders their widespread application. Regarding superconducting materials that can significantly break down this Tc barrier, in 1986 Muller of the IBM Zurich Research Institute
Since they announced that signs of superconductivity were observed in Ba-La-Cu-O-based composite oxides, the race to develop composite oxide superconducting materials has accelerated.
In other words, in 1986, the Tc of superconducting materials was 40K, but at the beginning of the following year (1987), Y-
A complex oxide superconducting material containing Ba-Cu-O based Cu _x O _y groups has been developed, and its Tc has reached approximately 93K. Furthermore, the development of superconducting materials has continued vigorously since then, and recently, the development of superconducting materials that exhibit superconducting phenomena at room temperature has been reported, although there are problems with safety and the like. As mentioned above, with the development of a composite oxide superconducting material containing Cu _x O _y groups that can be used at liquid nitrogen temperature (77K), there are expectations for the practical application of superconducting materials in the above-mentioned application fields. The level has been raised further. In order to put superconducting materials into practical use, what is necessary is the development of processing techniques such as forming superconducting materials into wires and films. Among these processing techniques, methods of forming a composite oxide superconducting film on the surface of a base material using sputtering method and electron beam evaporation method have been attempted, and recently Formation of coatings by laser vapor deposition or plasma spraying has been investigated. [Problems to be Solved by the Invention] However, when a film of a composite oxide superconducting material containing Cu _x O _y groups is formed on the surface of a base material by laser vapor deposition or plasma spraying, laser If the film is deposited as-deposited or plasma-sprayed as-is, the amount of oxygen in the film components becomes insufficient, and a film having desired superconducting properties cannot be formed. Therefore, a film of a composite oxide superconducting material containing Cu _x O _y groups is formed on the surface of the base material by laser evaporation method or plasma spraying method, and the resulting laser evaporated as-deposited film or plasma The as-sprayed superconducting material is heated to a predetermined temperature in an oxygen-containing atmosphere, held at that temperature for a predetermined time, and then cooled at a predetermined rate. Attempts have been made to impart superconducting properties to these materials. However, the above-mentioned heating and
In order to perform heat treatment consisting of holding and cooling, large-scale equipment is required, and there are problems such as cracking and melting of the film and distortion of the substrate due to high-temperature heating. . Therefore, the object of the present invention is to
When producing a superconducting material in which a film of a composite oxide superconducting material containing Cu _x O _y groups is formed, the insufficient oxygen in the film components is efficiently replenished without causing cracks in the film, and thus An object of the present invention is to provide a method for manufacturing a superconducting material having a film having excellent superconducting properties. [Means for solving the problem] This invention forms a film of a composite oxide superconducting material containing Cu _x O _y groups on the surface of a base material, and then
The superconducting material thus obtained is housed in a container, the container is maintained in an oxygen-containing atmosphere with a pressure of 10 Torr or less, and an electrode is placed parallel to the superconducting material at a predetermined distance from the film of the superconducting material. and causing a high frequency discharge to occur between the electrode and the superconducting material, thereby exciting oxygen present in the high frequency discharge region and causing the oxygen to permeate into the film of the superconducting material, and By applying a bias voltage to the superconducting material and imparting positive polarity to the superconducting material, the penetration of the oxygen into the film is promoted, thereby replenishing oxygen into the film components and adding to the film. It is characterized by providing excellent superconducting properties. The superconducting material in this invention, for example,
It is prepared using a laser vapor deposition apparatus as shown in the figure or a plasma spray apparatus as shown in FIG. The laser evaporation apparatus shown in FIG.
, a vapor deposition source 5 provided in a vacuum container 4, and a laser generator (not shown) for emitting a laser a toward the vapor deposition source 5. 6 is a heater for heating the base material 2; Cu _x as vapor deposition source 5
A composite oxide sintered body containing an O _y group is used, and a base material 2 is placed above a vapor deposition source 5 . Next, the pressure inside the vacuum container 4 is reduced to a predetermined degree of vacuum, and the laser a
is irradiated onto the vapor deposition source 5 to cause particles evaporated from the vapor deposition source 5 to adhere to the surface of the base material 2 heated by the heater 6. Thus, Cu _x on the surface of the base material 2
A superconducting material 1 on which a film 3 of a composite oxide superconducting material containing an O _y group is formed is prepared. The plasma spraying apparatus shown in FIG.
and a thermal spray nozzle 7 provided in the vacuum vessel 4,
Tungsten electrode 8 provided on thermal spray nozzle 7
and a power source 9 connected between the thermal spray nozzle 7 and the tungsten electrode 8. Vacuum container 4
The base material 2 is disposed inside facing the thermal spray nozzle 7.
Next, the pressure inside the vacuum container 4 is reduced to a predetermined degree of vacuum,
A working gas such as argon or helium and powder of a composite oxide superconducting material containing Cu _x O _y groups are supplied into the thermal spray nozzle 7 , and the power source 9 is activated to cause the thermal spray nozzle 7 to reach the tungsten electrode 8 . Generates a plasma jet towards the enemy. In this way, a superconducting material 1 is prepared in which a film 3 of a composite oxide superconducting material containing Cu _x O _y groups is formed on the surface of the base material 2 . Next, the superconducting material 1 prepared as described above is placed in a container 10 shown in FIG. Then, as shown in FIG. 1, the coating 3 of the superconducting material 1
An electrode 11 is arranged parallel to the superconducting material 1 at a predetermined interval from the superconducting material 1. A conducting wire 12 is connected between the superconducting material 1 and the electrode 11, and a high frequency power source 13 is provided in the middle of the conducting wire 12. A conductive wire 14 whose one end is attached to the positive electrode side of a power source 15 for applying a bias voltage is connected to the superconducting material 1 . Bias voltage application power supply 15
The negative electrode side of is grounded by a conducting wire 14'. The inside of the container 10 is maintained in an oxygen-containing atmosphere with a pressure of 10 Torr or less, and the high frequency power source 13 is operated in this state. As a result, high frequency discharge occurs between the electrode 11 and the superconducting material 1. Inside the container,
Since the pressure is in a vacuum or near-vacuum state of 10 Torr or less, low-temperature plasma is generated between the electrode 11 and the superconducting material 1. Therefore, oxygen in the atmosphere existing in the high frequency discharge region becomes excited and radical, and the film 3 of the superconducting material 1
penetrate inside. Furthermore, by the bias voltage application power supply 15,
A bias voltage is applied to the superconducting material 1, and positive polarity is given to the superconducting material 1, so that oxygen ions with negative polarity existing within the high frequency discharge region are
Oxygen is electrically adsorbed to the film 3 of the superconducting material 1, and the permeation of oxygen into the film 3 is promoted. In this way, the insufficient oxygen in the components of the film 3 is replenished, and a layer with excellent superconducting properties is formed on the surface of the base material 2.
A superconducting material in which a film 3 of a composite oxide superconducting material containing Cu _x O _y groups is formed is manufactured. When the superconducting material 1 has a width greater than a certain extent, the electrode 11 is moved in the width direction of the superconducting material 1 while discharging. By doing so,
Oxygen is uniformly supplied over the entire surface of the coating 3 of the superconducting material 1. Note that electrodes (not shown) are arranged on the surface of the film 3 of the superconducting material 1 along its length,
High frequency discharge may be caused between this electrode and the aforementioned electrode 11 arranged at a predetermined distance from the superconducting material 1. Next, the present invention will be explained using examples. [Example] As a composite oxide sintered body as a vapor deposition source, Y _1.2
Diameter 20mm, thickness with a composition of Ba _0.6 CuO _x
A 10 mm disc-shaped composite oxide sintered body was used, and a rectangular shape made of yttrium-stabilized zirconia (YSZ) with a side length of 15 mm and a thickness of 1 mm was used as the base material for the evaporation target. Using a plate, a film of superconducting material was formed on the surface of the substrate under the following conditions using the laser vapor deposition apparatus shown in FIG. (a) Vacuum degree of vacuum container: 10 ^-2 Torr (oxygen atmosphere) (b) Heating temperature of base material: 700℃ (c) Type of laser beam: Carbon dioxide laser (d) Laser beam output: 300W (e) Laser beam irradiation time: 5 minutes In this way, a superconducting material was prepared in which a 2 μm thick film having a composition of Y _0.3 Ba _0.6 Cu ₁ O _x was formed on the surface of the base material. Next, high-frequency discharge and bias voltage were applied to this superconducting material using the apparatus shown in FIG. 1 under the following conditions to replenish oxygen into the film components, thereby producing a superconducting material of the present invention. (a) Atmosphere inside the container: O ₂ : 100% (b) Pressure inside the container: 1Torr (c) Frequency of high frequency power supply: 13.56MHz (d) Output of high frequency power supply: 500W (e) Bias voltage: 80V (f ) High frequency discharge time: 100 hours For comparison, comparative superconducting material No. 1 made of as-deposited superconducting material, and comparative superconducting material No. 1 made of as-deposited superconducting material, and comparative superconducting material treated by the same method as above except that no bias voltage was applied. Material No. 2 was manufactured. Regarding the superconducting materials of the present invention and comparative superconducting materials No. 1 and No. 2 manufactured as described above, each
Tc (superconducting critical temperature) and Jc (critical current density) at 77K were investigated by four-terminal resistance measurement method. The results are shown in Table 1.

〔Effect of the invention〕

As described above, according to the present invention, when producing a superconducting material in which a film of a composite oxide superconducting material containing Cu _x O _y groups is formed on the surface of a base material, there is Oxygen is efficiently replenished in a low-temperature state without cracking or melting the film, thus producing an industrially useful effect that allows the production of a superconducting material having a film with excellent superconducting properties.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of supplying oxygen to the film components of a superconducting material by the method of the present invention, and FIG. FIG. 3 is a schematic sectional view showing a laser vapor deposition apparatus, and FIG. 3 is a schematic sectional view showing a plasma spraying apparatus for producing a superconducting material. In the drawings, 1... superconducting material, 2... base material, 3... film, 4... vacuum vessel, 5... vapor deposition source, 6... heater, 7... thermal spray nozzle, 8... tungsten electrode, 9 ...Power supply, 10...Container, 1
DESCRIPTION OF SYMBOLS 1... Electrode, 12... Conducting wire, 13... High frequency power supply, 14... Conducting wire, 15... Power supply for bias voltage application.

Claims (1)

[Claims] 1. A film of a composite oxide superconducting material containing a Cu _x O _y group is formed on the surface of a base material, and then the superconducting material thus obtained is placed in a container, and the inside of the container is heated to 10 Torr or less. By maintaining an oxygen-containing atmosphere at a pressure of By exciting oxygen present in the discharge region to allow the oxygen to penetrate into the film of the superconducting material, and applying a bias voltage to the superconducting material to impart positive polarity to the superconducting material. A method for producing a superconducting material, characterized in that the permeation of the oxygen into the film is promoted, thereby replenishing oxygen into the film components and imparting excellent superconducting properties to the film.