JPH05163005A - Production of oxide superconductor current-limiting device - Google Patents

Abstract

PURPOSE:To provide a method for producing an oxide superconductor current- limiting device having a large film thickness, a uniform and high critical current over a large area and, therefore, capable of improving the current-limiting effect. CONSTITUTION:By a method for producing an oxide superconductor current- limiting device according to the first invention in this patent, a metal alkoxide or a metal acetylacetonate mainly composed of a cation which is a constituting component of the oxide superconductor is hydrolyzed in a solution containing the above-mentioned substance to generate a sol- or gel-state compound containing the above-mentioned cation. The resultant sol-or gel-state compound is used for preparing an electrolytic solution and, in the electrolytic solution, a cathode composed of a metallic substrate 5 or a substrate coated with a metal coating 7 and an anode are set. A voltage is applied between both the electrodes to form a film-shaped oxide superconductor 6 on the substrate 5 followed by heat treatment. This invention is thus characterized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a conductor which conducts a current by using an oxide superconductor or a current limiting conductor capable of limiting an excessive current such as a short-circuit current, and an oxide superconducting limit. The present invention relates to a method for manufacturing a superconducting film for a flow conductor.

[0002]

2. Description of the Related Art In a superconductor, when any one of the critical temperature, the critical current, and the critical magnetic field exceeds the value, the superconducting state is destroyed, and the superconducting state is established and the electric resistance is increased. Research and development on superconducting fault current limiters (elements) that limit excessive currents by utilizing this phenomenon have become active in recent years. The technology of this field in general is described in, for example, the Institute of Electrical Engineers of Japan, Volume B, 110, No. 9, p. 705 (1990). Among these, a fault current limiter element using a superconducting limit fluid using an oxide superconductor has recently been drawing attention.
The structure of the element used for this is a simple structure in which a pair of electrodes are formed by depositing a metal such as silver, gold or indium on a part of the superconductor using vapor deposition or paste on a rod-shaped or plate-shaped superconductor. It is something. As a typical example, Advances in Superconductivity, pp. 691 (198)
There is one shown in 8). This uses a sintered body of Y-Ba-Cu-based oxide superconducting powder to form a zigzag (meaner structure) sheet by the doctor blade method,
The current is limited by increasing the resistance in the normal conducting state when a current exceeding the critical current flows. However, in such a sintered body (linear, rod-shaped, or plate-shaped), the critical current cannot be generally increased, so that the short-circuit current can be limited only by a small proportion. ..

Therefore, current limiting conductors (elements) to which a film-shaped superconductor formed on a base material is applied have been considered. Due to the progress of film forming technology, it has recently become possible to obtain an oxide superconducting thin film capable of passing a very large critical current. In addition, since the film-shaped one has better cooling characteristics than the above-described one such as a linear one, there is a possibility that a stabilizer may not be necessary, and further, there is an advantage that the resistance is easily increased. As a typical example using such a superconducting thin film,
Proceedings of 7th Joint Lecture on Applied Physics 28P-W-
12 (page 87). However,
In the case of using an oxide superconducting thin film, a composition deviation tends to occur when the film thickness is increased, and it is easy to peel off because the adhesion strength of the film to the substrate is low, and the composition becomes heterogeneous when formed in a large area. For this reason, it is inevitable that a large defect can be obtained only in the case of a small area of several mm square or less. Therefore, even in the current limiting device to which such a superconducting thin film is applied, the rate at which the fault current can be limited must be reduced. Further, the drawback that the metal of the terminal portion is easily peeled off is still unavoidable.

[0004]

As described above,
Conventional current limiting conductors (elements) have drawbacks in both linear, rod-shaped and plate-shaped sintered bodies and thin film-shaped ones.
It has been impossible to obtain a current limiting conductor in which the short-circuit (accident) current can be limited to a large extent and the electrode metal serving as a terminal portion is firmly formed.

That is, an object of the present invention is to manufacture a current-limiting conductor using an oxide superconductor, which has a large film thickness and is homogeneous and has a large critical current over a large area, so that the current-limiting effect can be enhanced. Method, method for producing a current limiting conductor having a large current limiting effect, in which a metal forming a terminal portion is strongly formed, and an oxide superconducting current limiting conductor superconducting film capable of producing a conductor having a large current limiting effect It is to provide a manufacturing method.

[0006]

According to a first aspect of the present invention, there is provided a method for producing an oxide superconducting current limiting conductor, comprising a metal alkoxide or metal acetylacetate containing a cation which is a constituent of the oxide superconductor as a main component. In a liquid containing nato,
A sol or gel-like compound containing the above cations is produced by hydrolysis, the obtained sol or gel-like compound is used as an electrolytic solution, and a metal base material or a base material having a metal coating in the electrolytic solution is used as a cathode, separately. A feature is that an anode is provided, a voltage is applied between both electrodes to form a film-shaped oxide superconductor on the substrate, and then heat treatment is performed.

In the method for producing an oxide superconducting current limiting conductor according to the second aspect of the present invention, a base material made of metal or a base material having a metal coating is used as a cathode in a liquid containing and dispersed oxide superconductor powder. Then, another anode is provided, a voltage is applied between both electrodes to form a film-shaped oxide superconductor on the substrate, and then a predetermined metal salt soluble in the liquid is added to the electroless method. Alternatively, a heat treatment is performed after a metal coating to be an electrode terminal is formed on a part of the oxide superconducting film by an electrolytic method.

In the method for producing an oxide superconducting current limiting conductor according to the third aspect of the present invention, an oxide is formed on the surface of a base material by oxidizing a base material composed of a metal constituting the oxide superconductor and an alloy containing silver. It is characterized in that a superconducting film is formed and a metal coating to be an electrode terminal is formed on a part of the oxide superconducting film.

In the method for producing a superconducting film for an oxide superconducting current limiting conductor according to the fourth aspect of the present invention, after a silver coating layer is formed on a substrate, it is mainly heated in a gas atmosphere containing ozone or active oxygen species. The oxide superconducting film is formed on the silver coating layer.

[0010]

The method for producing the oxide superconducting current limiting conductor according to the first aspect of the present invention uses an electrodeposition method utilizing so-called electrophoresis. This is a method in which particles of an oxide superconductor are dispersed in a dispersion medium containing an anode and a cathode, and electrified to deposit charged particles on the surface of a conductive electrode.
Therefore, it is necessary to use a metal or a metal-coated base material as the electrode. At this time, according to the preliminary experiments conducted by the present inventors, it was found that the oxide superconductor particles were positively charged in most of the solvents, so that the base material should be the cathode.

The present invention is particularly characterized by the electrolytic solution of the electrodeposition method. That is, a sol or gel solution by a so-called sol-gel method is used as an electrolytic solution in which an oxide superconductor is dispersed in a dispersion medium. This method is known as a method for forming a coating film and also for producing fine particles such as a metal oxide film, and uses a metal alkoxide or metal acetylacetonate dissolved in an organic solvent as a starting material. .. Hydrolysis reaction can be caused by adding water to this, and finally, hydroxides of these metals or fine particles of oxides can be finally produced.

The present inventors have found that in a liquid containing a metal alkoxide or metal acetylacetonate whose main component is a cation which is a constituent of an oxide superconductor, a sol or gel containing the above cation by hydrolysis. It was found that the product in which the solid compound was produced was the most suitable as the electrolytic solution for the electrodeposition method utilizing the above-mentioned electrophoresis. In the present invention,
After forming the oxide superconducting film on the substrate by the electrodeposition method, heat treatment can be applied to improve the superconducting characteristics.

In the method for manufacturing an oxide superconducting current limiting element according to the second aspect of the present invention, a metal terminal is formed in an electrolytic solution immediately after the oxide superconducting film is formed, and then heat treatment is performed to reduce the connection resistance. Based on the finding that a film can be obtained and that when the oxide superconducting film is formed in an electrolyte containing silver ions, the crystallinity of the superconducting film after heat treatment is improved and the critical temperature is also improved. Is.

The second method for manufacturing the oxide superconducting current limiting element also uses an electro-deposition method utilizing so-called electrophoresis. This is a method in which particles of an oxide superconductor are dispersed in a dispersion medium containing an anode and a cathode, and electrified to deposit charged particles on the surface of a conductive electrode. Therefore, it is necessary to use a metal or a metal-coated base material as the electrode. At this time, according to the preliminary experiments conducted by the present inventors, it was found that the oxide superconductor particles were positively charged in most of the solvents, so that the base material should be the cathode.

In the present invention, after forming an oxide superconducting film on a substrate, a metal salt soluble in a liquid is added, and a metal coating is formed on a part of the oxide superconducting film by an electroless method or an electrolytic method. Form. Finally, this is heat-treated to obtain an oxide superconducting current limiting conductor. As described above, when heat treatment is performed after forming the metal that will be the electrode terminal following the oxide superconducting film, the adhesion of the metal film to the superconducting film is improved compared to the case where the metal film is formed after heat treating the superconducting film. There is an effect of doing.

Furthermore, when at least one of the method of adding a silver salt in the solution and the method of using a metal containing silver as an anode during the formation of the superconducting film, the superconductivity after the final heat treatment is used. The crystallinity and superconducting properties of the film are improved.

In the method for producing an oxide superconducting current limiting conductor according to the third aspect of the present invention, an oxide superconductor coating is formed on the surface of a base material by oxidizing an alloy made of a metal constituting the oxide superconductor. Method is used. In the present invention, in this case, an alloy containing silver is used as the base material together with the metal forming the oxide superconductor. According to the study of the present inventors, when silver is contained, when the alloy surface is made into a superconductor by an oxide, the crystallinity of the oxide superconducting film produced is improved by some action of silver, Since it was found that the superconducting property was improved along with this, the manufacturing method of the third invention of the present invention was completed.

In the present invention, a metal coating is formed on a part of this superconducting film as an electrode terminal portion to provide an oxide superconductor current limiting element. Furthermore, the use of an alloy containing silver as described above has the effect of improving the adhesion of the metal coating to the superconducting film, as compared with the case of not containing silver.
Moreover, it was revealed that the contained silver does not adversely affect the characteristics of the superconductor.

In the method for producing a superconducting film for an oxide superconducting current limiting conductor according to the fourth aspect of the present invention, a sputtering method, a CVD method, an oxide superconducting film method, a vapor deposition method, or the like, which is widely used, is used. The membrane method is used. In the present invention, a silver coating layer is formed on the substrate before forming the oxide superconducting film. Then, the oxide superconducting film is formed in a gas atmosphere containing mainly ozone or active oxygen species. It has been found that the formation of the silver coating in advance improves the crystallinity of the superconducting film and raises the critical temperature, which brings about the advantage of increasing the current limiting effect.

Further, at the time of producing the superconducting film, at least silver is deposited on the substrate at the same time as the oxide superconducting material, or at least the raw material of the oxide superconducting material containing silver or a compound of silver is used. By using any one of the methods, the critical temperature and the crystallinity are further improved, so that the final current limiting effect can be further improved.

[0021]

【Example】

Example 1 This example illustrates the first invention of the present invention. FIG. 1 shows an example of the manufacturing method according to this embodiment. In the figure, (1)
Is a glass electrolytic cell, (2) is an electrolytic solution (sol or gel solution), (3) is an anode, and (4) is a cathode made of a conductive base material. The composition of the final oxide superconducting film was changed to YBa ₂ Cu ₃ O.
The cation metal alkoxides Y, Ba and Cu isopropoxide were dissolved in 150 ml of isopropyl alcohol at a predetermined ratio so as to obtain _7-x . This solution was kept warm at 80 ° C. and then hydrolyzed while slowly adding 10 ml of water thereto, and a gel-like black brown precipitate was formed. This solution was used as the electrolytic solution (2). A strip-shaped silver plate having a width of 5 mm and a length of 20 mm in which the central portion was narrowed was used as a substrate, and this was used as a cathode (4). A platinum spiral was used as the anode (3), the solution was sufficiently stirred with an ultrasonic cleaner, and then electrodeposited on the cathode at a constant DC voltage of 50 to 1000 V at a solution temperature of 50 ° C. After this, in an oxygen stream,
It heat-processed at 50 degreeC for 5 hours, and gradually cooled to room temperature. Both ends of this fired film were coated with gold by sputtering, lead wires were attached to the gold, and a current limiting device using the oxide superconducting current limiting conductor shown in FIG. 2 was manufactured. The superconducting film has a critical temperature of 85 K, a thickness of 2.5 μm, and a gold electrode portion has a thickness of about 1 μm.
It was m. In FIG. 2, (5) is a base material (silver substrate), (6) is a superconducting film (Y-based oxide superconducting film), (7) is a gold coating for electrode terminals, and (8) is a lead wire. In addition, when the superconducting film (6) was produced in various thicknesses other than the above-mentioned thickness, it was possible to produce a thick film of about 30 μm without any problem, and even if such a thick film had a critical temperature of 85K. It was found to be similar to the above case.

For comparison, a screen printing method and an electron beam evaporation method are respectively used to form a film having the same composition as that of the present invention and having the same film thickness on the same substrate, and in an oxygen stream at 950 ° C. Two kinds of oxide superconducting current limiting devices were manufactured by a conventional manufacturing method in which after heat treatment for 5 hours, gold electrode terminals were formed by a sputtering method. The critical temperature of each superconductor was 83K.

Each of the above-mentioned three kinds of oxide superconducting current limiting devices was subjected to a current limiting experiment in an alternating current circuit (frequency: 50 Hz) having an estimated short circuit current of 400 A by cooling in liquid nitrogen. The current limiting peak value, which is a measure of device performance, was measured. As a result, 39A according to the present invention, 76A by screen printing, and 71A by the sputtering method were obtained. As is clear from these results, it was found that the oxide superconducting current limiting element manufactured by the manufacturing method according to the first aspect of the present invention can limit the short-circuit current to about 1/2 that of any conventional method. .. When the critical current densities of the above three types of current limiting devices at the liquid nitrogen temperature were measured, the results were 2200 in the present invention, screen printing, and electron beam evaporation method.
0 A / cm ² , 1200 A / cm ² and 13000 A / c
It was m ² . Since the three types of elements all have the same shape and the thickness of the superconducting film is the same, it is estimated that the current limiting effect is mainly due to the magnitude of the value of the critical current density.

That is, it was revealed that the manufacturing method according to the first aspect of the present invention can manufacture a current limiting element having a high critical current density and a large current limiting effect. The reason for this is currently unknown, but the method of the present invention deposits fine particles such as metal hydrates produced by the sol-gel method on the substrate as it is by utilizing the energy during electrodeposition. It is presumed that this is because the superconducting film has good crystallinity and homogeneity due to subsequent heat treatment.

Example 2 This example also illustrates the first aspect of the present invention. Using the same device as that used in Example 1 and shown in FIG. 1, the composition of the target oxide superconducting film was set to BiSrC.
Acetoacetonate of Bi, Sr, Ca, and Cu at a predetermined ratio so as to be aCu ₂ O _x is 130 at 80 ° C.
It was dissolved in ml of ethyl alcohol. Hydrolysis was carried out by gradually adding 10 ml of distilled water to which a small amount of aqueous ammonia was added to the solution. As a result, a liquid containing a gelled hydrolysis product was obtained. This solution was used as an electrolytic solution, and a strip-shaped silver plate similar to that used in Example 1 was used as a substrate, which was used as a cathode. Platinum spiral is used as the anode, the solution is thoroughly stirred with an ultrasonic cleaner, and then the solution temperature is 60 ° C for 50 to 15
Electrodeposition was performed on the cathode with a DC constant voltage of 00V. Then, it heat-processed at 865 degreeC in air for 8 hours, and was annealed to room temperature. Both ends of this fired film were covered with gold by sputtering, and lead wires were attached to the gold, and an oxide superconducting current limiting device shown in FIG. 2 was produced. The critical temperature of the superconducting film was 85 K, the thickness was 2.5 μm, and the thickness of the gold electrode portion was about 1 μm.

For comparison, a screen printing method and an electron beam evaporation method are respectively used to form a film having the same composition and the same film thickness as those of the present invention on the same base material, and then at 865 ° C. in air. Two types of oxide superconducting current limiting devices were manufactured by a conventional manufacturing method in which a gold electrode terminal was formed by a sputtering method after heat treatment for a long time. The critical temperature of each superconducting film was 83K.

The current limiting device of the present invention and the conventional three types of current limiting devices were put into liquid nitrogen for cooling and connected to the same circuit as in Example 1 to conduct a current limiting experiment. As a result, under the same measurement conditions as in Example 1, the one of the present invention was able to limit the estimated short-circuit current 400A to 38A. On the other hand, 75A by screen printing and 70A by electron beam evaporation method.

As is clear from these results, the oxide superconducting current limiting device according to the manufacturing method of the first invention of the present invention is more excellent than any of the conventional methods, as in the embodiment.
It was found that the short-circuit current could be limited to about / 2. Incidentally, when the critical current density at the liquid nitrogen temperature of the above three kinds of current limiting devices was measured, in the present invention, by screen printing, by electron beam evaporation method,
The values were 21500 A / cm ² , 12300 A / cm ² and 13100 A / cm ² , respectively.

That is, according to the manufacturing method of the first invention of the present invention, it became clear that it is possible to produce a current limiting conductor having a high critical current density and a large current limiting effect. The reason for this is that, as described above, the solution containing fine particles generated by the sol-gel method was used as an electrolytic solution as it was, and the fine particles of the superconducting film were heat-treated after applying the energy of electrodeposition to deposit the fine particles on the substrate. It is presumed that this is because the superconducting properties were improved because the crystallinity was good and uniform.

The base material used in the first invention of the present invention includes ceramics such as Al ₂ O ₃ , SiO ₂ , MgO and SrTiO ₃ , single crystals, gold, silver, stainless steel, copper,
Examples thereof include metals such as nickel and alloys thereof. When an insulating material such as ceramics or single crystal is used as a base material, it is necessary to apply a conductive metal coating in order to serve as a cathode during electrodeposition, and as such a coating, gold, silver, Metallic coatings of carbon, nickel, chrome, etc. are suitable. However, it is desirable that the above-mentioned metal or metal coating is hard to react with the oxide superconducting film, and it is most preferable to use silver.

In the first invention of the present invention, the metal alkoxide or acetylacetonate (derivative) which is a component constituting the oxide superconductor used as a starting material is
Any structure and form can be used. As the metal alkoxide, even if the number of carbon atoms of the alkoxy group is any, it can be used as long as it is soluble in a suitable solvent. For example, preferred specific examples include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group and a butoxy group. Acetylacetonate is a compound in which at least one acetylacetonate group is bonded to a metal element, and as long as the basic skeleton does not change, for example, a hydrogen atom may be substituted with a fluorine atom, a hydrocarbon group or the like. Solvents for dissolving these compounds include alcohols,
A wide range of organic solvents such as ketones and esters can be mentioned. When hydrolyzing these starting materials, the degree of progress of hydrolysis varies depending on the amount of water added, conditions such as temperature and pH value of the solution, and the solution containing the product becomes a sol, or It becomes a gel. In the present invention, any property can be used,
It was confirmed by experiments that these can be used as electrolytes. Further, depending on the element, the fine particles of the hydrolysis product may be a metal oxide, but in general, it is often an amorphous hydrate or hydroxide. Since these are completely converted into metal oxides by firing and become superconductors, heat treatment is required after electrodeposition in the present invention.
It is generally known that the temperature of heat treatment varies depending on the type of superconducting material, and it is well known that the temperature is in the range of approximately 800 to 1000 ° C.

As the anode, a metal electrode used in general electrolysis can be used, but it is preferable to use an insoluble electrode which is stable in a liquid such as platinum or iridium, rhodium or carbon used in the examples. preferable.

After forming the oxide superconducting film on the substrate,
As the method of forming the metal coating to be the electrode terminal, any of the thin film forming methods such as the sputtering method, the electroless plating method, the electrolytic plating method, and the pressure bonding method may be used as described in the embodiments. Suitable metals are silver, gold and indium.

By the way, in Examples 1 and 2, Y-based and Bi-based materials were used as examples of oxide-based superconducting materials.
The effects of the first invention of the present invention are not limited to these, but are La type, T
It was confirmed by the same examination as in the examples that the oxide superconducting materials such as 1-type and Nd-type oxides were expressed.

Example 3 This example illustrates the second aspect of the present invention. FIG. 1 shows an example of the manufacturing method of the present invention. 2 g of YBa ₂ Cu ₃ O _7-x oxide superconductor powder prepared by dry powder method using oxides and carbonates of each component as starting materials
Was dispersed in 100 mg of methyl ethyl ketone together with 10 mg of water to obtain an electrolytic solution (2). A strip-shaped silver plate having a width of 5 mm and a length of 20 mm in which the central portion was narrowed was used as a substrate, and this was used as a cathode (4). Platinum spiral is used as the anode (3), and after stirring thoroughly with an ultrasonic cleaner, the liquid temperature is 5
Superconducting powder was electrodeposited on the cathode at a constant DC voltage of 50 to 1000 V at 0 ° C. Subsequently, the central portion of this superconducting film was covered with an insulating tape, and both ends were electrolessly plated with gold. At this time, potassium gold cyanide in the electrolytic solution (2),
Ammonium chloride, sodium citrate and water were added and the liquid temperature was adjusted to 90 ° C. to obtain a plating liquid. After plating, the plate was heat-treated at 950 ° C. for 5 hours in an oxygen stream and gradually cooled to room temperature. In this way, the oxide superconducting current limiting device shown in FIG. 2 was manufactured. The critical temperature of the superconducting film was 86 K, the thickness was 3.5 μm, and the thickness of the gold electrode portion was about 1 μm. Further, when the superconducting film was produced by using various thicknesses other than the above-mentioned thickness, it was possible to produce a thick film of about 30 μm without any problem, and even if such a thick film had a critical temperature of 86K, It turned out to be similar to.

For comparison, a screen printing method and an electron beam evaporation method are used to form a film having the same composition and the same film thickness as that of the present invention on the same substrate, and the film is formed in an oxygen stream at 950 ° C. After the heat treatment for 5 hours, the gold electrode terminals are formed by the sputtering method according to the conventional manufacturing method.
A kind of oxide superconductor current limiting device was fabricated. The critical temperature of each superconductor was 83K.

The above-mentioned three types of oxide superconducting current limiting devices were each put into liquid nitrogen and cooled, and a current limiting experiment was conducted in an AC circuit (frequency 50 Hz) with an estimated short circuit current of 400 A, and the performance of each current limiting device was examined. The current limiting wave height, which is a guideline for, was measured. As a result, 35A according to the present invention, 76A by screen printing, and 70A by the sputtering method were obtained. As is clear from these results, it was found that the oxide superconductor current limiting device according to the manufacturing method of the present invention can limit the short-circuit current to 1/2 or less as compared with any of the conventional methods. The critical current densities of the above three types of current limiting devices at the liquid nitrogen temperature were measured, and 25000 A / cm ² and 12 were obtained for the present invention, screen printing, and electron beam evaporation method, respectively.
It was 00 A / cm ² and 13000 A / cm ² . Since all three types of elements have the same shape and the thickness of the superconducting film is also the same, it is estimated that the current limiting effect is mainly due to the magnitude of the value of the critical current density.

That is, according to the manufacturing method of the second aspect of the present invention, it became clear that a current limiting element having a high critical current density and a large current limiting effect can be manufactured.

When the same measurement was repeated, the same results as above were obtained with good reproducibility. However,
In the conventional two types of current limiting elements, the repeated measurement resulted in the peeling of the gold of the electrode terminal portion, resulting in a problem that it could not be used. That is, the conventional manufacturing method, in addition to the performance inferior to that of the present invention, the adhesion strength of the metal coating to be the electrode terminal to the superconducting film is low,
It was found that it was easily peeled off by heat shock. This lack of adhesion strength is caused by the heat treatment after the oxide superconducting film is formed in the case of the manufacturing method according to the second aspect of the present invention, when the gold to be the electrode terminal is formed thereafter, and also when the heat treatment is further performed thereafter. It happened as well. That is, in the manufacturing method of the second invention of the present invention, it is necessary to form a metal coating to be an electrode terminal after forming the oxide superconducting film, and then perform a heat treatment, whereby a highly adherent metal coating for an electrode terminal is formed. Is obtained.

Example 4 The same electrolytic solution as in Example 3 was used, and 1 g of silver nitrate was added to the solution, but under the same conditions as in Example 3, the superconducting film was formed on a silver substrate of the same shape. I put on my clothes. When the critical temperature of the superconducting film formed by this was measured, 88 K was obtained. In addition, it was confirmed by X-ray diffraction that the crystallinity of the Y-based superconducting film was improved as compared with the case of performing electrodeposition without adding silver nitrate of Example 1.

Further, a Y-based superconducting film was electrodeposited under the conditions of Example 3 using a silver-palladium alloy as an anode instead of adding silver nitrate. At the time of electrodeposition, it was expected that a small amount of silver ions would be eluted from the anode into the electrolytic solution, and the same effect as when the above silver salt was added would occur. As a result, the generated superconducting film has a critical temperature of 88 K, which is higher than that in the case of Example 3, and the crystallinity of the Y-based superconducting film is improved in the same manner as in the case of Example 3 just as described above. Also X
It was analyzed and confirmed by the line diffraction method.

Further, in the above two cases, after potassium gold cyanide, potassium cyanide and dipotassium phosphate were added to the respective liquids and the same insulating coating as in Example 3 was applied to the central portion of the formed superconducting film. At 70 ° C., a gold coating to be an electrode terminal was electroplated with a current density of 0.1 A. These were heat-treated in an oxygen stream at 940 ° C. for 8 hours and then gradually cooled to room temperature to manufacture an oxide superconducting current limiting element according to the second aspect of the present invention. The critical current densities of both superconducting films were 38000 A / cm ² , which was higher than that of Example 3. When these two types of current-limiting conductors were subjected to the same measurements as in Example 3 to investigate the performance, the estimated short-circuit current of 400 A could be limited to 25 A. That is, the performance was improved as compared with the case of the method of the present invention shown in Example 3.

The reason for this is that, as described above, when electrodepositing the oxide superconducting film, a silver salt was added to the solution or a metal containing silver was used as an anode, and therefore, it was confirmed by analysis. It is considered that this is because the crystallinity of the Y-based superconducting film is improved and the superconducting properties such as the critical temperature and the critical current density are improved.

As the electrolytic solution (dispersion medium of oxide superconductor particles) used in the second invention of the present invention, in addition to the methyl ethyl ketone used in Examples 3 and 4, methyl isobutyl ketone, ethyl acetoacetate, ethyl alcohol, isopropyl. Examples include a wide range of organic solvents such as alcohols, alcohols such as acetone and acetylacetone, ketones and esters. It is generally difficult to make superiority or inferiority with respect to these solvents, but it seems that the efficiency of electrodeposition is improved by adding several% of water in each case. The voltage applied at the time of electrodeposition varies depending on the type of solvent, but is about several tens to 2000 V.

As the anode, a metal electrode used in general electrolysis can be used. However, an insoluble electrode which is stable in a liquid such as platinum or iridium, rhodium or carbon used in Examples 3 and 4 can be used. It is preferable to use.

After forming the oxide superconducting film on the substrate,
As a method for forming the metal coating to be the electrode terminal, either the electroless method or the electrolytic method may be used as described in the third and fourth embodiments.

As the metal salt added to the electrolytic solution, a metal salt that dissolves in the solution is suitable, but a silver or gold salt most suitable for the final electrode terminal is desirable.

Further, as in Example 4, if a silver salt is added to the liquid or a metal containing silver is used as the anode when forming the superconducting film, the reason is not clear at present. The crystallinity and superconducting properties of the generated superconducting film are improved. The silver salts added at this time include silver nitrate, silver acetate,
Examples of silver cyanide, potassium silver cyanide, and an anode material include pure silver, a silver-palladium alloy, and a silver-iridium alloy.

In Examples 3 and 4, the Y-based material was used as an example of the oxide-based superconducting film, but the effect of the second invention of the present invention is not limited to the Y-based material, but Bi-based, Tl-based, and Nd-based materials. It was confirmed by the same examination as in the example that the oxide was expressed in any of the above oxide superconducting materials.

Example 5 Rectangular Y-2B having a width of 5 mm, a length of 20 mm and a thickness of 1 mm
An alloy in which 3% by weight of Ag was added to a-3Cu was used as a base material. This was heat-treated in an oxygen atmosphere at 910 ° C. for 15 hours and then at 550 ° C. for 5 hours to form an oxide superconducting film on the surface. Then, the central portion of this superconducting film was covered with an insulating tape, and both ends were electrolessly plated with gold. As the electrolytic solution, potassium cyanide, ammonium chloride, sodium citrate and water were added and the solution temperature was adjusted to 90 ° C. After plating, a lead wire was attached to the gold coating, and an oxide superconducting current limiting element was manufactured by the manufacturing method of the third invention of the present invention. The superconducting film has a critical temperature of 86K and a thickness of 0.
The thickness of the gold electrode portion was 6 μm, and the thickness was about 1 μm.

For comparison, an oxide superconductor manufactured by a conventional manufacturing method in which a base material made of an alloy having exactly the same shape as the above and made of no Ag is oxidized under the same conditions to form gold electrode terminals by an electroless method. A current limiting device was prototyped. The critical temperature of the superconductor was 83K, which was 3K lower than that of the present invention. Further, a sintered body of an oxide superconductor having the same shape as that of the present invention was produced by a powder method which is a conventional production method using a nitrate or an oxide of Y, Ba or Cu, and a gold electrode which was also used as an electrode. To form a current limiting device. The critical temperature of this device was 84K.

Each of the above three types of current limiting elements was put into liquid nitrogen and cooled, and a current limiting experiment was conducted in an AC circuit (frequency 50 Hz) with an estimated short circuit current of 400 A. A certain limiting current peak value was measured. In this circuit, the estimated short circuit current without a current limiting element is 400
Since it was A, the performance was compared depending on how far it could be limited by each current limiting element.

As a result, 65A according to the present invention, 98A according to the prior art without addition of silver, and 85A according to the powder sintering method.
Became. As is clear from this result, the third aspect of the present invention
It has been found that the oxide superconducting current limiting device manufactured by the manufacturing method of the present invention can limit the short-circuit current more efficiently than the conventional method. That is, according to the manufacturing method of the third invention of the present invention, it became clear that a current limiting element having a large current limiting effect can be easily manufactured. The reason for this is currently unclear. However, according to the analysis and evaluation of the above-mentioned two kinds of samples by the X-ray diffraction method, the crystallinity of the superconducting film in the case of the present invention was better than that in the conventional one, so that the alloy substrate It is presumed that the inclusion of silver will improve the current limiting effect due to the above-described crystallinity improving effect.

When the same measurement as above was repeated, the same result that the current limiting effect of the current limiting element manufactured by the method of the present invention was excellent in any case was obtained with good reproducibility. On the other hand, in the two types of elements manufactured by the conventional manufacturing method, the gold coating on the electrode terminal portion was peeled off during repeated measurement, and the measurement became impossible. That is, it was found that the current limiting element according to the present invention not only has a large current limiting effect, but also that the metal coating to be the electrode can be formed more firmly than the conventional one.

Further, the same examination was carried out using a metal other than gold, such as silver or indium, as the electrode terminal. In any case, the electrode terminal portion was found in the current limiting device manufactured by the method of the present invention. The above results were obtained in which it was confirmed that the metal coating of 1 was strengthened. The reason for this is not clear, but the silver contained in the alloy that is the base material diffuses into the superconductor generated during the oxidation treatment,
It is presumed that, in addition to the above-mentioned crystallinity improving effect, it has some function of enhancing the adhesion of the coating metal.

By the way, in Example 5, the Y-based material was used as an example of the oxide-based superconducting material, but the effect of the present invention is not limited to the Y-based material, and any oxidation of Bi-based, Tl-based, Nd-based, etc. It was confirmed by the same examination as in the example that it also appeared in the superconducting material.

That is, as the base alloy used in the third invention of the present invention, it is possible to use any alloy whose surface becomes an oxide superconductor by oxidation. As such an example, Bi-Sr-Ca-Cu alloy, Nd-Ce-C
Examples include u alloys and La-Sr-Cu alloys. It is possible to use Ag containing these alloys. Ag
Although the content rate of can be arbitrarily selected, a range of about 1 to 10% of the whole base alloy is suitable.

As the gas atmosphere used when forming the superconducting film by the oxide superconducting film as the base material in the third aspect of the present invention, an oxygen gas atmosphere, an oxygen plasma, an active oxygen atmosphere such as ozone gas, etc. may be used. It is possible.

As a method for forming a metal coating to be an electrode terminal after forming an oxide superconducting film by the method of the present invention on a substrate, a vapor phase film forming method, an electroless plating method, an electrolytic plating method or a pressure bonding method. Either may be used. Although various metals can be used for the electrode terminals, silver or gold is preferable.

Example 6 A rectangular MgO substrate having a width of 5 mm and a length of 20 mm was used as a base material. About 0.5 μm by sputtering
Thickness of silver coated. Next, a metal of each component was used as a starting material, and a YBa ₂ Cu ₃ O _7-x oxide superconducting film was formed by an electron beam evaporation method. At this time, ozone 5%
Oxygen gas containing is introduced to adjust the gas pressure to 1.5 × 10 ⁻⁴
The temperature was adjusted to Torr, and after film formation, the film was gradually cooled to room temperature in this atmosphere. Thus, the superconducting film was manufactured by the manufacturing method of the fourth invention of the present invention. Then, the central portion of this superconducting film was covered with an insulating tape, and both ends were electrolessly plated with gold. As the electrolytic solution, potassium cyanide, ammonium chloride, sodium citrate and water were added and the solution temperature was adjusted to 90 ° C. After plating, a lead wire was attached to the gold coating to fabricate an oxide superconducting current limiting device. The critical temperature of the superconducting film was 86 K, the thickness was 0.6 μm, and the thickness of the gold electrode portion was about 1 μm.

For comparison, the same electron beam evaporation method as that described above was used, and the same type of substrate was not coated with silver, and the same composition and film thickness as those of the present invention were applied in an oxygen stream of the same gas pressure. An oxide superconductor current limiting device was manufactured by a conventional method for manufacturing a superconducting film, in which a film was formed, and then slowly cooled, and then gold electrode terminals were formed by an electroless method. The critical temperature of the superconductor was 83K, which was 3K lower than that of the present invention.

Each of the above two types of current limiting elements was put into liquid nitrogen and cooled, and a current limiting experiment was conducted in an AC circuit (frequency 50 Hz) with an estimated short circuit current of 400 A. A certain limiting current peak value was measured. as a result,
The present invention is 55A and the conventional one is 98A. As is clear from this result, the oxide superconductor current limiting element using the superconducting material obtained by the manufacturing method of the fourth invention of the present invention has a short-circuit current about half that of the conventional method. It turns out that the current can be limited. That is, it was revealed that the manufacturing method of the present invention can manufacture a superconducting film for a current limiting element having a large current limiting effect.

The reason for this is not clear at present. However, according to the analysis and evaluation of the above-mentioned two kinds of samples by the X-ray diffraction method, the crystallinity of the superconducting film was better in the case of the present invention. It is presumed that if the film is formed in a gas atmosphere containing ozone or an active oxygen species after forming, the current limiting effect is improved due to the above-described crystallinity improving effect.

When the same measurement as the above was repeated, it was found that the oxide superconducting current limiting element using the superconducting film obtained according to the fourth invention of the present invention was excellent in any case. The results were obtained with good reproducibility.

Example 7 In the same experiment as in Example 6, a method was used in which silver was vapor-deposited at the same time as the material for the oxide superconducting film was vapor-deposited. Separately from this, Y, Ba and Ag20% -Cu alloys were used as starting materials for the Y-based superconducting film of Example 6.
A Y-type superconducting film having the same composition and the same composition was formed on a substrate having the same shape and the same shape by the electron beam evaporation method under the same conditions as in Example 6 except for the above. When the critical temperature of the oxide superconducting film formed by this was measured, 88 K was obtained in both cases. In addition, it was confirmed by an X-ray diffraction method that the crystallinity of the Y-based superconducting film was further improved in all cases, as compared with the case of performing the film formation in which the silver was not vapor-deposited in Example 1.

Further, in the above-mentioned case, after applying the same insulating coating as in Example 6 to the central portion of the formed superconducting film,
Under the same conditions, a gold coating to be the electrode terminals was electroless plated. Thus, an oxide superconducting current limiting element was produced.

Example 6 of these two types of current limiting devices
When the performance was investigated by carrying out the same measurement as in the above case, it was possible to limit the estimated short circuit current of 400 A to 38 A in all cases. That is, the performance was further improved as compared with the case shown in Example 6. The reason for this is that, when depositing the oxide superconducting film as described above, silver is deposited on the base material at the same time as the superconducting film raw material or the raw material containing the silver alloy is used. As confirmed by analysis, the crystallinity of the Y-based superconducting film was further improved,
It is presumed that this is due to improvement in superconducting properties such as critical current density.

The base material used in the fourth invention of the present invention includes Al ₂ O ₃ , SiO ₂ , MgO, SrTiO ₃ and Z.
Ceramics such as rO ₂ and Y ₂ O ₃ , single crystals, metals such as gold, silver, stainless steel, copper and nickel, or alloys thereof can be used.

In the fourth invention of the present invention, it is necessary to previously form a silver coating layer having an arbitrary thickness before forming the superconducting film.
As this method, as shown in Examples 6 and 7, it is optimal to use the same method as that for forming the superconducting film. However, the present invention is not limited to this, and the silver coating layer may be previously formed by another film forming method. It was also confirmed that the silver coating layer must be applied even when silver is used as the base material, and the effect of the fourth invention of the present invention does not occur if such a coating is not formed.

In the fourth invention of the present invention, the gas atmosphere used when the superconducting film is formed after the substrate is coated with silver is one containing a directly active oxygen species such as oxygen plasma or ozone gas. However, it is also possible to use a gas species such as N ₂ O that easily generates active oxygen by decomposition. An arbitrary value may be used as the gas pressure at this time, because it greatly differs depending on the method used. For example, the CVD method generally requires a high gas pressure, and the sputtering method and the vapor deposition method have a low gas pressure.
(High vacuum) is normal. Further, the content ratio of ozone or active oxygen species in the gas can be arbitrarily selected.

As a method for forming a metal coating to be an electrode terminal after forming the oxide superconducting film according to the fourth aspect of the present invention on a base material, there are vapor phase film forming method, electroless plating method and electrolytic plating. Method or pressure bonding method may be used. Silver or gold is preferable for the electrode terminals.

As in Example 7, at least one of depositing silver on the base material at the same time as the oxide superconducting film or using a raw material for the oxide superconducting film containing silver or a silver compound. If the two methods are used, the crystallinity as well as the superconducting properties of the produced superconducting film are further improved, although the reason is not clear yet. As a film forming method used at this time, many methods such as a sputtering method, a CVD method oxide superconducting film method, and an evaporation method can be applied. Examples of silver or silver compounds include pure silver, silver oxide, silver alloys, silver nitrate, silver acetate, and silver chloride. Examples 6 and 7 are used so that their decomposition products do not adversely affect the superconducting film. The pure silver, an alloy of silver and a superconducting material, or silver oxide used in 1. is preferable.

By the way, in the examples, the Y-based material was used as an example of the oxide-based superconducting material, but the effect of the fourth invention of the present invention is not limited to the Y-based material, and Bi-based, Tl-based, Nd-based, etc. may be used. It was confirmed by the same examination as in the example that the oxide superconducting material was also expressed.

In the first to seventh embodiments, the case where the current limiting conductor is used for the current limiting element has been described. However, the present invention is not limited to this. For example, when the current limiting conductor is used as a conductor for conducting a normal current, It is needless to say that since the resistance at the time of energization can be made almost zero, there is no power loss, and when an excessive current flows, this can be limited.

[0075]

As described above, the first invention of the present invention is as follows.
A method for producing an oxide superconducting current limiting conductor, in a liquid containing a metal alkoxide or metal acetylacetonate containing a cation as a main component which is a constituent of the oxide superconductor,
A sol or gel-like compound containing the above cations is generated by hydrolysis, and the obtained sol or gel-like compound is used as an electrolytic solution. In this solution, a metal base material or a base material having a metal coating is used as a cathode, and another anode is used. And applying a voltage between both electrodes to form a film-shaped oxide superconductor on the substrate,
Next, by applying heat treatment, the current limiting effect
There is an effect that it is possible to obtain a current limiting conductor having a large (rate of limiting the short-circuit current).

A second aspect of the present invention is a method for producing an oxide superconducting current limiting conductor, wherein a metal substrate or a substrate having a metal coating is used as a cathode in a liquid containing a powder of an oxide superconducting material. Then, another anode is provided, a voltage is applied between both electrodes to form a film-shaped oxide superconductor on the substrate, and then a predetermined metal salt soluble in the liquid is added to the electroless method. Alternatively, by the electrolytic method, after forming a metal coating to be an electrode terminal on a part of the oxide superconducting film, by performing a heat treatment,
The current limiting effect (rate of limiting the short-circuit current) is large, and further, the current limiting conductor in which the metal coating to be the electrode terminal portion is firmly formed can be obtained.

The third aspect of the present invention is a method for producing an oxide superconducting current limiting conductor, in which a base material made of a metal constituting an oxide superconductor and an alloy containing silver is oxidized on the surface of the base material. By forming an oxide superconducting film and forming a metal coating that will become an electrode terminal on a part of the oxide superconducting film, the current limiting effect (rate of limiting the short-circuit current) is large, and the electrode terminal part There is an effect that it is possible to obtain a current limiting conductor having a strongly formed metal coating.

Furthermore, a fourth aspect of the present invention is a method for producing a superconducting film for an oxide superconducting current limiting conductor, which comprises forming a coating layer of silver on a substrate and then mainly using ozone or a gas containing an active oxygen species. By forming the oxide superconducting film on the silver coating layer in the atmosphere, it is possible to easily obtain a current limiting conductor having a large current limiting effect (rate of limiting the short-circuit current).

[Brief description of drawings]

FIG. 1 is a schematic diagram of a method for manufacturing an oxide superconducting current limiting device according to the first and second aspects of the present invention.

FIG. 2 is a schematic view of an oxide superconducting current limiting device obtained by the first and second inventions of the present invention.

[Explanation of symbols]

 1 Glass Electrolyzer 2 Electrolyte 3 Anode 4 Cathode 5 Base Material 6 Superconducting Film 7 Metal Film for Electrode Terminal 8 Lead Wire

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication H01L 39/16 ZAA 8728-4M H02H 9/02 ZAA Z 7335-5G (72) Inventor Sadajiro Mori Amagasaki 8-1-1 Tsukaguchi Honcho, Ichika, Central Research Laboratory, Mitsubishi Electric Corporation (72) Inventor Tatsuya Hayashi 8-1-1, Tsukaguchi Honcho, Amagasaki City Central Research Laboratory, Mitsubishi Electric Corporation

Claims (4)

[Claims] 1. A sol or gel-like compound containing the above cation is produced by hydrolysis in a liquid containing a metal alkoxide or metal acetylacetonate containing a cation as a main component, which is a constituent of an oxide superconductor. The obtained sol or gel-like compound is used as an electrolytic solution, and in this electrolytic solution, a metal base material or a base material having a metal coating is used as a cathode, and another anode is provided. A method for producing an oxide superconducting current limiting conductor, which comprises forming a film-shaped oxide superconductor on a substrate, and then performing heat treatment. 2. A substrate in which a metal substrate or a substrate having a metal coating is used as a cathode in a liquid containing an oxide superconductor powder dispersed therein, an anode is separately provided, and a voltage is applied between both electrodes. Form a film-shaped oxide superconductor on top, and then add a predetermined metal salt soluble in the liquid and electroless or electrolytic method to form electrode terminals on a part of the oxide superconducting film. A method for manufacturing an oxide superconducting current limiting conductor, characterized in that heat treatment is performed after forming the metal coating. 3. An oxide superconducting film is formed on the surface of the base material by oxidizing a base material composed of a metal forming the oxide superconductor and an alloy containing silver, and an electrode terminal is formed on a part of the oxide superconducting film. A method for producing an oxide superconducting current limiting conductor, which comprises forming a metal coating that becomes 4. After forming a silver coating layer on a substrate, in a gas atmosphere containing mainly ozone or active oxygen species,
A method for producing a superconducting film for an oxide superconducting current limiting conductor, which comprises forming an oxide superconducting film on a silver coating layer.