JPH0531496B2 - - 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,
Superconducting materials are expected to be applied to nuclear fusion reactors, power transmission cables, magnetic shielding materials, etc., and superconducting materials using the Syosefson 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 complex oxides, the race to develop complex 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 Ba-Cu-O composite oxide superconducting material 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 stability and the like. As mentioned above, the discovery of a superconducting material that can be used at liquid nitrogen temperatures (77K) has further raised expectations for the practical application of superconducting materials in the aforementioned application fields. 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. As one such processing technique, research has been conducted to form a composite oxide superconducting film containing Cu _x O _y groups on the surface of a base material using a laser vapor deposition method. FIG. 2 is a schematic vertical sectional view showing an example of an apparatus for forming a superconducting film by a laser vapor deposition method. As shown in FIG. 2, inside the decompression chamber 1,
A composite oxide sintered body 2 as a vapor deposition source is placed below the vapor deposition source, and a base material 3 as a vapor deposition target is placed above the vapor deposition source 2. Above the base material 3 is a heater 4 for heating the base material 3 to a predetermined temperature.
is provided. One side wall 1a of the decompression chamber 1 is provided with a laser transmission window 5 for irradiating a laser beam toward the vapor deposition source 2 in the decompression chamber 1, and a laser beam condensing window 5 is provided outside the laser transmission window 5. A condensing lens 6 is provided for this purpose. 7 is a gas exhaust port for discharging the gas in the reduced pressure chamber 1, and 8 is a gas supply port for supplying gas into the reduced pressure chamber 1. For example, a Y--Ba--Cu--O based composite oxide sintered body is used as the vapor deposition source. The interior of the decompression chamber 1 is maintained at a predetermined degree of vacuum, and a laser beam is irradiated from a laser beam generator (not shown) toward the sintered body 2 in the decompression chamber 1 through the laser transmission window 5 . The surface of the sintered body 2 irradiated with the laser beam is
It melts and evaporates, and the evaporated material is deposited on the surface of the substrate 3. Thus, on the surface of the substrate 3,
A superconducting material 10 on which a film 9 of a composite oxide superconducting material containing a Cu _x O _y group is formed is manufactured. [Problems to be Solved by the Invention] However, the above method has the following problems. (1) When using, for example, a Y--Ba--Cu--O based composite oxide sintered body as a vapor deposition source, this sintered body is manufactured as follows. That is, powdered yttrium oxide (Y ₂ O ₃ ), barium carbonate (BaCO ₃ ), and copper oxide (CuO) are blended and mixed in a predetermined ratio. The obtained mixture is molded into a predetermined shape, and then the molded body is fired in an oxygen atmosphere. Thus, Y-Ba-Cu-
An O-based composite oxide sintered body is obtained. In manufacturing the sintered body as described above,
If the thickness of the sintered body is thick, for example, exceeding 10 mm, oxygen will not penetrate sufficiently into the center of the compact during firing, resulting in a lack of oxygen in the center of the sintered body. As a result, as the laser beam irradiation progresses the melting of the surface of the sintered body, which serves as a deposition source, and the thickness of the sintered body becomes thinner, the oxygen content in the evaporated material from the sintered body decreases. As a result, the amount of oxygen in the film 9 formed on the surface of the base material 3 becomes insufficient. (2) As mentioned above, the surface of the Y-Ba-Cu-O based composite oxide sintered body as a vapor deposition source is melted and evaporated by laser beam irradiation, but
During this evaporation, the oxide in the composition of the sintered body is decomposed, and some oxygen is separated from the evaporated substance. Since this separated oxygen does not adhere to the surface of the base material 3, the amount of oxygen in the film 9 becomes insufficient. As stated in (1) and (2) above, when the amount of oxygen in the film 9 formed on the surface of the base material 3 is insufficient,
A film 9 having desired superconducting properties cannot be formed on the surface of the base material 3. Therefore, a low-pressure oxygen atmosphere of 10 ^-1 to 10 ^-4 Torr is created in the decompression chamber 1, and a laser beam is irradiated toward the evaporation source 2 in such a low-pressure oxygen atmosphere to reduce the evaporation from the evaporation source 2. Attempts have been made to compensate for the lack of oxygen in the film 9 by combining the substance with oxygen in the atmosphere. However, since the evaporated substances from the sintered body 2 and the oxygen in the decompression chamber 1 do not react in a short time, even the above-mentioned method cannot solve the shortage of oxygen in the film 9. Therefore, an object of the present invention is to form a composite oxide superconducting film containing Cu _x O _y groups on the surface of a substrate by a laser vapor deposition method without causing a shortage of oxygen in the film. An object of the present invention is to provide a method for producing a superconducting material that can form a film having superconducting properties. [Means for Solving the Problems] This invention provides Cu _x as a vapor deposition source in a reduced pressure chamber.
A composite oxide sintered body containing an O _y group and a base material as a deposition target are arranged, and the composite oxide sintered body is irradiated with a laser beam, and the composite oxide sintered body is irradiated with the laser beam. In a method for producing a superconducting material, in which a composite oxide superconducting film containing a Cu _x O _y group is formed on the surface of the base material by depositing an evaporated substance evaporated from a sintered body onto the surface of the base material. , maintaining an oxygen atmosphere in the reduced pressure chamber, and providing discharge electrodes on both sides of the evaporation flow in which the evaporated substance evaporated from the composite oxide sintered body reaches the base material, and between the electrodes. By applying a voltage and causing a discharge, oxygen present in the discharge region is excited to promote the combination of the oxygen and the evaporation substance, and the evaporation substance combined with oxygen is deposited on the surface of the base material, Thus, it is characterized in that the superconducting properties of the film are improved. Next, the present invention will be explained with reference to the drawings. FIG. 1 is a schematic vertical sectional view showing one embodiment of the method of the invention. As shown in Figure 1,
In the reduced pressure chamber 1, a composite oxide sintered body 2 as a vapor deposition source and a base material 3 as a deposition target are arranged,
A heater 4 for heating the base material 3 to a predetermined temperature is provided above the base material 3, and a laser transmission window 5 having a condensing lens 6 is provided on the side wall of the decompression chamber 1;
The provision of a gas outlet 7 and a gas inlet 8 is similar to the conventional method apparatus shown in FIG. In this invention, a laser beam irradiated from a laser beam generator (not shown) toward the composite oxide sintered body 2 in the reduced pressure chamber 1 through the laser transmission window 5 causes evaporated substances evaporated from the sintered body 2 to be transferred to the base material. Discharging electrodes 12 and 12' are provided on both sides of the evaporation flow 11 leading to the discharge point 3. Electrode 1
In the middle of the conductor 13 that interconnects 2 and 12',
A power source 14 is provided. By continuously blowing oxygen into the decompression chamber 1 through the gas supply port 8 and continuously discharging the gas in the decompression chamber 1 through the gas discharge port 7,
The inside of the decompression chamber 1 is maintained at a low pressure oxygen atmosphere of 10 ^-1 to ^{10 -4} Torr. A disk-shaped Y-Ba-Cu-O composite oxide sintered body 2 is arranged as a vapor deposition source, and a laser beam generator (not shown) passes through a laser transmission window 5 to the sintered body 2 in the decompression chamber 1. Irradiate the laser beam towards the target. The surface of the sintered body 2 irradiated with the laser beam melts and evaporates. The evaporated substance evaporated from the sintered body 2 in this manner becomes an evaporation flow 11 directed toward the base material 3 and adheres to the surface of the base material 3. At this time, a voltage is applied by the power supply 14 between the electrodes 12 and 12' provided on both sides of the evaporative flow 11, causing a discharge between the electrodes 12 and 12'.
As a result, oxygen in the atmosphere within the discharge region becomes excited. Therefore, since the evaporated stream 11 passes through such an excited oxygen atmosphere toward the base material 3, the evaporated substances in the evaporated stream 11 easily combine with oxygen, and the reaction between the two is promoted. In this manner, the evaporated substance combined with oxygen in the atmosphere adheres to the surface of the base material 3, so that a superconducting material 10 having a film 9 with excellent superconducting properties can be manufactured. [Example] Next, the present invention will be explained with reference to an 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 as the base material for the deposition object, with a side length of 20 mm.
A rectangular plate made of yttrium stabilized zirconia (YSZ) with a thickness of 0.5 mm was used. Using the above-mentioned vapor deposition source, a film of a superconducting material was formed on the surface of the above-mentioned base material according to the method of the present invention under the following conditions. (a) Vacuum degree of decompression chamber: 10 ^-2 Torr (oxygen atmosphere) (b) Heating temperature of base material: 800℃ (c) Type of laser beam: Carbon dioxide laser (d) Laser beam output: 300W (e) Laser beam irradiation time: 5 minutes (f) Type of discharge: High frequency discharge (g) Cap between electrodes: 70 mm (h) Power of high frequency discharge: 50 W As a result, a 7 μm thick film is formed on the surface of the base material. was able to form. Next, the base material on which such a film has been formed is
Heated to a temperature of 930℃ in an oxygen atmosphere,
After maintaining this temperature for 30 minutes, it was slowly cooled to room temperature. Thus, Y _0.3 Ba _0.65 on the surface of the substrate
A superconducting material of the present invention was produced in which a composite oxide superconducting film having a component composition of Cu ₁ O _x was formed. The Tc (critical temperature) and Jc (critical current density) of the superconducting material produced as described above were investigated using a four-terminal resistance measurement method. For comparison, a comparative superconducting material was manufactured by the same method as above except that no discharge was performed, and its Tc and Jc were examined by the above measurement method. This concentration is shown in Table 1.

〔Effect of the invention〕

As described above, according to the present invention, when producing a superconducting material in which a composite oxide superconducting film containing Cu _x O _y groups is formed on the surface of a base material by a laser vapor deposition method, it is possible to There is no shortage of oxygen, and therefore a film having excellent superconducting properties can be formed, which is an industrially useful effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view showing an embodiment of the method of the present invention, and FIG. 2 is a schematic vertical sectional view showing an example of the conventional method. In the drawings, 1... decompression chamber, 2... sintered body,
3...Base material, 4...Heater, 5...Laser transmission window, 6...Condensing lens, 7...Gas exhaust port, 8...
... Gas supply port, 9 ... Film, 10 ... Superconducting material,
11... Evaporation flow, 12, 12'... Electrode, 13...
...Conductor, 14...Power supply.

Claims (1)

[Claims] 1. A composite oxide sintered body containing a Cu _x O _y group as an evaporation source and a base material as an evaporation target are placed in a reduced pressure chamber, and the composite oxide sintered body is placed in a reduced pressure chamber. A laser beam is irradiated onto the base material, and the evaporated material evaporated from the composite oxide sintered body by the laser beam irradiation is deposited on the surface of the base material, thereby depositing Cu _x O on the surface of the base material. In the method for manufacturing a superconducting material forming a composite oxide superconducting film containing _{a y} group, an oxygen atmosphere is maintained in the vacuum chamber, and the evaporated substance evaporated from the composite oxide sintered body evaporates to the base material. Discharging electrodes are provided on both sides of the flow, and by applying a voltage between the electrodes and causing a discharge, oxygen present in the discharge area is excited and the bond between the oxygen and the evaporated substance is promoted. . A method for producing a superconducting material, which comprises depositing an evaporated substance bonded with oxygen on the surface of the base material, thereby forming a film with excellent superconducting properties on the surface of the base material.