JPS63310951A - Production of superconductor - Google Patents

Abstract

PURPOSE:To deposit a superconductor over a large area at a high rate by jetting particles of Y-Ba-Cu-O type composite oxide on a substrate with a plasma flame. CONSTITUTION:Particles of composite oxide contg. an element A (Sc, Y or a lanthanoid) an, element B (an alkaline earth element such as Ba or Ca), Cu and oxygen are prepd. The composite oxide particles having 0.1mum-1mm particle size are mixed into a plasma flame and jetted on a substrate to deposite the composite oxide on the substrate and to produce a superconductor. The pref. molar ratio of the elements A, B to Cu [(A+B)/Cu] is 0.5-2.5. The superconductor consisting of the composite oxide particles bonded to one another without changing the state of the particles can be deposited on the substrate over a large area at a high rate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing superconductors. In particular, it relates to a method for manufacturing compound superconductors.

Conventional technology As high-temperature superconductors, niobium nitride (NbN) and germanium niobium (Wb5G) are used as M16 type binary compounds.
e), etc., but the superconducting transition temperature of these materials was at most 24°. On the other hand, peropskite-based ternary compounds are expected to have even higher transition temperatures,
A high-temperature superconductor based on Ba-La-Cu-0 was proposed (
J., G., Bednorz and K., Mu.
ller, Zeit Schrift Fairphysik (
B)-C
Ona6n8ea Matter 64.189-19
3 (1986)).

Furthermore, it has recently been proposed that the Y-Ba-Cu-0 system is a higher temperature superconducting material. (Literature) (M, Ni, W
U, etc., Physical Review Letters (Physic
al Review Letters) Mol
, 58 ff19゜The details of the superconducting mechanism of Y-Ba-Cu-0-based materials are not clear, but the transition temperature may be higher than the liquid nitrogen temperature, making it difficult to use conventional binary compounds as high-temperature superconductors. More promising properties are expected.

Problems to be Solved by the Invention However, Y-Ba-Cu-0 based materials can only be formed through the process of sintering using current technology.
It is only available in ceramic powder or block form. On the other hand, when this kind of material is put to practical use in electric wires, etc.
It is extremely difficult to form a thin film epitaxially at high speed.

The present inventors have discovered that high-temperature superconductors are formed when particles of this type of material are deposited in a plasma flame, and based on this discovery, a novel method for manufacturing superconductors has been discovered.

Means for Solving the Problems The basic composition of the superconductor formed by the manufacturing method of the present invention is that particles of a composite oxide containing Mu element, B element, Cu, and oxygen and having a particle size of, for example, 0.1 μm to 1H are used. The composite oxide is mixed into a plasma flame and sprayed toward the surface of the substrate, thereby depositing the composite oxide on the substrate. The present inventors have discovered that this type of superconductor can be formed by plating a composite oxide onto a substrate. Here, M is at least one of Sc, Y, and lanthanum-based elements (atomic number 57-71), B
represents at least one kind of Ila group elements such as Be, Mg, Ca, Sr, and Ba.

Function: The method for producing a superconductor according to the present invention is characterized in that particles of a composite oxide containing a superconductor are formed into a thin film on a substrate using plasma flame. In other words, when particles of a composite oxide containing Mu elements, B elements, and Cu are injected onto a substrate together with a plasma flame, which is a gas fluid at several thousand degrees Celsius, if the particle diameter is less than 0.1 μm, they will evaporate or melt. It became an amorphous oxide of Shitam element, B element, and Cu, and did not exhibit superconductivity even after subsequent heat treatment. Furthermore, when the particle size is larger than 11111f, even if a superconducting phenomenon is exhibited, the critical current at the superconducting transition temperature is too small to be put to practical use. However, the present inventors have found that the particle state of the composite oxide can be maintained on the substrate only when using particles of the composite oxide containing Mu element, B element, Cu, and oxygen and having a particle size of 0.1 μm to 1 mm. However, how about the particles?
This led to the confirmation of the excellent superconducting phenomenon.

Therefore, by using the present invention, it is possible to deposit superconductors, which could only be obtained in powder or blocks through conventional sintering, at a very high speed and over a large area.

Embodiments An embodiment of the present invention will be described with reference to the drawings. In the following description, a Y-Ba-Cu-0-based compound oxide is used as an example of a composite oxide containing Mu element, B element, and Co.

Powders of BaCO3, 1205 and CuO were used as raw materials and mixed at a molar ratio of Y, Ba and Cu of 1:2:3. This mixed powder was fired at 900°C for 18 hours to form a Y-Ba-Ou-0 based composite oxide. Thereafter, the composite oxide is pulverized to a particle size of less than 0.1 μm.
0.1 to 1 μm, 1 μm to 10 μm wing.

10μ! 11~100μm, 100μ! It~1f
It was classified into 6 groups: those larger than l, 1, and TI.

When we investigated the crystallinity of these composite oxides, we found that all particle size groups exhibited crystallinity comparable to that of conventional composite oxides that exhibit superconducting phenomena.

The outline of the apparatus will be explained with reference to FIG. In order to generate a plasma flame 16 with a high temperature, 20K was applied between the Cu electrodes at 22°23.
A power of W was applied. At this time, the flow rate was 101/m2. In order to mix the composite oxide particles 16 into the plasma flame 16 of 31.degree. from the outside of the plasma flame,
Using Mr as the carrier gas for 17m, 1sf/
m composite oxide particles were mixed into the flame. The distance from the Cu anode 22 to the substrate 11 was set to 31, and the atmosphere gas 18 at the position where the composite oxide was plated on the substrate 11 was oxygen and the gas pressure was set to 76 o Torr. The substrate 11 was made of Cu wire, and the substrate temperature was 40°C.

Under the above conditions, composite oxides whose particle sizes were divided into six groups were plated onto the substrate 11. Film thickness: 10 in forging time of 10 minutes
The particle diameter was 0 μm, and the adhesion rate was 60 cm, regardless of the particle size.

After finishing, it was heat treated in an oxygen atmosphere for 800'02 hours.
It was slowly cooled over 3 to 4 hours.

The composite oxide 12 formed as described above was applied with constant current (21,
The voltage at A) was measured.

As a result, when the particle size was less than 0.1 μm, the composite oxide was amorphous and did not exhibit superconductivity. When the particle size was larger than 1 mm, it exhibited a voltage of several volts and became a kind of resistor. Almost no voltage was exhibited only when the particle diameter was 0.1 μm to 1 μm. In particular, it was confirmed that when the particle size is 1 μm to 100 μm, superconductivity is exhibited with almost no voltage even when the current is several μm. Further, the superconducting transition temperature of the composite oxide that exhibited superconducting phenomenon was 90°.

Although the details of the above phenomenon are not clear, there is a superconductor in the particles of the composite oxide, and when this superconductor passes through the plasma flame, part of the surface layer melts and adheres to the substrate. Then, while maintaining the superconductor, it combines with other superconductors. At this time, if the particle size is less than 0.1μ,
It is thought that the composite oxide on the substrate became amorphous because the entire particle melted or evaporated. The superconductors bonded in this way began to exhibit electrical conduction, and it seems that the superconducting phenomenon was confirmed for the composite oxide as a whole. At this time, when the particle size is larger than 1 mm, the electrically conductive region between the superconductors is small, so a critical current is reached with a very small amount of current, and it is thought that the state shifts from superconductivity to normal conductivity.

Here, the molar ratio of Y, Ba, and Cju in the composite oxide was set to 1:2:3, but the present inventors not only investigated the molar ratio in detail, but also investigated the I also went there. As a result, a superconducting phenomenon was confirmed when the molar ratio of Mu element, B element, and Cu was set to Mu + B O, S≦≦2.6 Cu.

Here, the plasma flame 16 was formed using Mu τ as an inert gas, but other gases such as He, Ne, 16. Kr may be used singly or in a mixture. If the flow rate is inert gas, 5
If the flow rate is between 201/m and 201/m, it becomes possible to deposit the composite oxide 12, and if the flow rate is less than 6117m, the gas temperature will become too high and a solid solution of the composite oxide 12 will be formed. If it was too large, it would not adhere to the substrate 11. Superconductivity was confirmed when the distance from the anode 22 to the substrate 11 was 3 to 2 oa/l. When the value became larger than 201, the critical current decreased rapidly.

Nitrogen, oxygen, and hydrogen as plasma flame 1e.

Single carbon dioxide gas or a mixture of carbon dioxide gases may be used, and such multi-molecule qs has a gentler temperature gradient than inert gases and has a lower temperature gas temperature, so the flow rate is less than 1.
0 to 501/MiI4, a superconducting phenomenon was confirmed.

When the distance from the anode 22 to the substrate 11 was 10 to 30, the adhesion rate was 60% or more, when it was less than 101, the composite oxide 12 became amorphous, and when it was greater than 30α, the critical current decreased rapidly.

Although Mr was used as the gas for transporting the particles of the composite oxide 12, other inert gases or nitrogen, oxygen, hydrogen, or carbon dioxide gas alone or in combination may be used, and the gas may react with the composite oxide 12. Any gas will do as long as it does not. Further, a superconducting phenomenon is exhibited at a gas flow rate of 2 to sgz=. Increase the flow rate to 2 (
If it is less than 1/m, the transport of the composite oxide particles 15 becomes unstable, so that an amorphous state was observed in the forged composite oxide 12, and no superconducting phenomenon could be confirmed. Moreover, when more than 5 1/i was flowed, a kind of resistor was formed on the substrate.

Although pure oxygen gas is used as the atmospheric gas, it may be an inert gas, air, carbon dioxide gas, or any gas that does not reduce the composite oxide 12.

The gas pressure of the atmospheric gas is 10TOττ to 760 Torr.
If r, superconducting phenomenon was confirmed. When the temperature was less than 10 TOrr, the plasma flame 1e directly heated the substrate and the composite oxide 12 became a solid solution, and when the temperature was greater than 76° Torr, it hardly adhered to the substrate.

Although 17 m of composite oxide was supplied into the plasma flame for 1 s, a superconducting phenomenon was confirmed within the range of 5 to 309/m, and the critical current reached several MU.

When the composite oxide was less than 69/i, the formed composite oxide exhibited an amorphous state, and no superconducting phenomenon was observed. When the complex oxide was supplied at a rate greater than 309/mis, the formed complex oxide became a kind of resistor.

To create a plasma flame, a voltage was applied to the electrodes to form a plasma flame. Although Cu is used here as the material of the electrode, it is extremely susceptible to sputtering.

At least one type of Mu element, B element, or an alloy may be used for the cathode, and if it is a composite oxide containing Mu element, B element, and Cu that exhibits conductivity, it can have the effect of serving as a source of composite oxide particles. Indicated. In addition, Cu is used for the anode, which becomes extremely high temperature.
By using a composite oxide containing at least one type of Mo element, B element, or an alloy, as well as five conductive elements, B element, and Cu, the critical current is nearly an order of magnitude higher than that of an anode made of high temperature resistant materials such as Mo and W. It made a difference. this is,
It is thought that the constituent atoms of the composite oxide adhere to the particles of the composite oxide at the time of fracture, increasing the bonding between the particles.

In this example, the substrate temperature was 400°C, but 100°C
Superconductivity was observed at temperatures ranging from 10 to 900 degrees Celsius. 100
If the temperature was below 900°C, the composite oxide on the substrate became a kind of resistor, and if it was higher than 900°C, it was in an amorphous state. Further, when the substrate temperature was increased from 200° C. to 700″C, the critical current reached several KA/d.

In this example, the composite oxide particles 16 are exposed to the plasma flame 1.
However, by supplying only the external particles 16 to the plasma flame 16 without using a carrier gas, it is possible to forge a large area for a long time due to the limitation of the size of the plasma flame. I was able to get dressed. In addition, when the composite oxide particles 16 were simultaneously supplied with at least one type of gas among an inert gas or polyatomic molecules to form a plasma flame, a superconductor could be easily formed at an arbitrary position.

In this example, after forming the composite oxide 12 on the substrate 11 with plasma flame 16, heat treatment was performed in an oxidizing atmosphere, but the superconducting phenomenon was confirmed even without heat treatment. However, we confirmed that heat treatment increases the critical current at the superconducting transition temperature by more than an order of magnitude. In addition, we confirmed that the same effect as the heat treatment performed by heating the substrate was confirmed by using at least one type of inert gas or oxidizing gas such as oxygen, carbon dioxide, or air as a means of heat treatment, and by using plasma flame. did. When the composite oxide 12 is formed on the substrate 11, the substrate 11 is formed at a high temperature of several hundred degrees Celsius, and superconductivity is operated at a low temperature, for example, liquid nitrogen temperature (-196 degrees Celsius), so in particular, the substrate 11 and the composite oxide are The present inventors found that the adhesion with the coating 12 deteriorates and the coating 12 is often damaged.As a result of investigating the detailed thermal characteristics of the substrate for various materials, the inventors found that the linear expansion coefficient of the substrate is 1O-
6 (1/C), it has been confirmed that the above-mentioned coating will not be damaged and can be used in practical use. For example, if quartz glass with α × 10-6 is used as the substrate, the coating 12 will have countless cracks and will not be continuous. The present inventors have confirmed that the resulting film is unsuitable for practical use.

Furthermore, the present inventors have discovered that there is an optimal material for the base body 11 shown in FIG. 2 in terms of functionality.

That is, as the base 11, Ou, Ni, Ti
, Mo.

The present inventors have confirmed that metals such as Ta, W, Mn, and Fe or alloys containing these metal elements, such as nichrome and stainless steel, are effective.

Furthermore, it was confirmed that when a heat-resistant coating was formed on the base 11, the critical current at the superconducting transition temperature increased.

As a nitride for the heat-resistant coating, for example, TiN is used.

TaN, Mol, NbN, WN, Mn
N, etc., but carbides such as TaC, TiC, NbC, M
oO, WC, MnC, etc., but NbO, T as oxides
The present inventors have confirmed that iO, TaO, β0°ZrO, TO, etc. are effective.

The effect of these heat-resistant coatings is that the composite oxide 1 on the base 11
It is thought that this prevents the particles from forming a solid solution with the substrate 11 when they break and adhere.

Further, in order to form the highly crystalline complex oxide coating 12 on the surface 13 of the substrate 11, a single crystal substrate is effective. The inventors of the present invention investigated the optimal substrate material in detail and found that the substrate 11 was magnesium oxide, sapphire (α-rhos) + spinel.

It was confirmed that single crystals such as strontium titanate, silicon, and gallium arsenide are effective. However, since this is for effectively growing a highly crystalline coating 12 on the surface 13, it is sufficient if at least the substrate surface 13 is a single crystal.

The present inventors have confirmed that so-called sintered porcelain is more effective as a base material than a single crystal when processing this type of superconductor into an arbitrary shape, such as a cylinder, and have also found the most suitable porcelain material. I found it. That is, the present inventors have found that alumina, magnesium oxide, derconium oxide, steatite, forsterite, beryllia, spinel, etc. are used as the porcelain substrate to provide optimal adhesion of the superconducting coating 12 to the substrate 11 through processing of the substrate, etc. confirmed. In this case as well, it is preferable that even the surface of the substrate is made of this type of porcelain, as in the case of single crystals. When forming the composite oxide 12 on the substrate 11, Cu wire was used in this example, but the pretreatment of the Cu wire before breaking caused a difference of nearly one order of magnitude in the critical current of the composite oxide. The present inventors discovered.

That is, when a copper wire is chemically etched and broken, the critical current decreases compared to a wire that is not etched. The present inventors have developed other molded Cu wires and C
As a result of examining U-plates, it was found that the critical current was lower when etched, regardless of the drawing method, extrusion method, or rolling method. Regarding the differences in forming methods, the rolled copper wire obtained the highest critical current compared to other forming processes. This seems to be because scratches so small that they cannot be observed with an electron microscope are created during the molding process, and composite oxides are formed along these scratches during bonding, and furthermore, the composite oxides are bonded to each other. Also magnesium oxide.

The same phenomenon as described above was also confirmed in single crystal substrates such as sapphire and silicon, and in ceramic materials such as alumina, steatite, and spinel.

The details of changes in superconducting properties due to changes in the constituent light and B of this kind of superconductor of B-Cu-0 based composite oxide are not clear. However, it is true that M indicates trivalence and B indicates divalence. The explanation has been given using Y as an example of the five elements, but Sc, La, and even lanthanum series elements (atomic numbers 57 to 71) change the superconducting transition temperature, but do not change the essential characteristics of the invention. .

Also, in B elements, Sr, Ca, Ba, etc.ff
Although the change in the group a element changes the superconducting transition temperature by about 10°, it does not essentially change the characteristics of the present invention.

Effects of the Invention The method for producing a superconductor according to the present invention is characterized in that particles of a composite oxide containing a superconductor are formed into a thin film on a substrate using plasma flame. That is, when particles of a composite oxide containing Mu element, B element, and Cu are injected onto a substrate together with a gas fluid at several thousand degrees Celsius called plasma flame, the Mu element, B element, and Cu will evaporate or melt.
It became an amorphous oxide, and even after subsequent heat treatment, no superconducting phenomenon was observed. However, the present inventors have determined that the particles containing human element, B element, Cu, and oxygen have a particle size of 0.
It was confirmed that only when composite oxide particles of 1 μm to 1 mm were used, the particles were bonded together while maintaining the composite oxide particle state on the substrate, and superconductivity was also confirmed. In addition, since particles of 11 rIl or less are used,
It becomes easily possible to deposit one conductor over a large area and at high speed.

Therefore, by using the present invention, it is possible to deposit superconductors, which could only be obtained in powder or blocks through conventional sintering, at a very high speed and over a large area.

As explained above, according to the method for manufacturing a superconductor of the present invention, it is formed in the form of a thin film in the form of a metal line, so unlike powder or blocks of sintered bodies, it is practical for manufacturing superconductor cables and coils. be done.

In particular, there is a possibility that the transition temperature of this type of compound superconductor is room temperature, so the range of practical application is wide, and the industrial value of the present invention is high.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus used in a superconductor manufacturing method according to an embodiment of the present invention, and FIG. 2 is a basic configuration diagram of a superconductor formed by the superconductor manufacturing method of the present invention. 11...Substrate, 12...Composite oxide, 16
...Plasma flame, 15...Composite oxide particles. Name of agent: Patent attorney Toshio Nakao and one other personj!
! 1 Mouth 2nd figure 121 zu one go one one ini and 2? ! 11 bases

Claims (1)

[Scope of Claims] (1) Particles of a composite oxide containing element A, element B, Cu, and oxygen and having a particle size of 0.1 μm to 1 mm are mixed into a plasma flame and injected toward the substrate, and the A method for producing a superconductor, comprising depositing a composite oxide on the substrate. Here, element A is Sc, Y, and lanthanum-based elements (
Element B represents at least one element among alkaline earth elements (atomic numbers 57 to 71). (2) Calcinate a composite oxide containing element A, element B, Cu, and oxygen, and reduce the particle size of the composite oxide to 1 μm to 100 μm.
The method for manufacturing a superconductor according to claim 1, wherein the superconductor is made to have a diameter of μm. (3) The molar ratio of element A, element B, and Cu in the fired composite oxide is set to 0.5≦(A+B)/Cu≦2.5. Method for manufacturing superconductors. (4) After forming the composite oxide on the substrate,
The method for manufacturing a superconductor according to claim 1, wherein the superconductor is subjected to heat treatment. (5) As plasma flame, Ar, He, Ne, Kr,
The method for producing a superconductor according to claim 1, characterized in that at least one inert gas of monoatomic molecules such as Xe is used. (6) The method for manufacturing a superconductor according to claim 1, characterized in that at least one type of polyatomic molecular gas such as nitrogen, oxygen, hydrogen, carbon dioxide, etc. is used as the plasma flame. (7) Claim 5 characterized in that the plasma flame contains inert gas at a flow rate of 5 to 20 l/min.
A method for producing a superconductor as described in Section 1. (8) Flow rate of 10 to 20 l/min in plasma flame
7. The method for producing a superconductor according to claim 6, characterized in that the superconductor comprises a polyatomic molecular gas of: (9) A plasma flame is formed by mixing composite oxide particles into at least one type of inert or polyatomic molecular gas to form a plasma flame. A method for manufacturing superconductors. (10) A method for manufacturing a superconductor according to claim 1, characterized in that particles of the composite oxide are mixed into the plasma flame from outside and injected onto the substrate. (11) From the outside of the plasma flame, the flow rate is 2 to 5 l/
The particles of the composite oxide are transported using at least one kind of gas selected from among an inert gas such as Ar, He, Ne, Kr, and Xe, or a polyatomic molecular gas such as oxygen, nitrogen, hydrogen, and carbon dioxide, and the 2. The method of manufacturing a superconductor according to claim 1, wherein particles of the composite oxide are mixed into a plasma flame. (12) Claim 1, characterized in that at least one inert gas such as He, Ar, Ne, Kr, or Xe is used as the atmosphere gas at the position where the composite oxide is plated on the substrate. A method for manufacturing the superconductor described. (13) Atmosphere gas: 10 to 760 Torr
The method for producing a superconductor according to claim 1, characterized in that at least one oxidizing gas such as oxygen, carbon dioxide, or air is used at a gas pressure in the range of r. (14) As a substrate, linear thermal expansion coefficient α>10^-^6(1
2. The method for manufacturing a superconductor according to claim 1, wherein a material having a temperature of (15) Magnesium oxide, sapphire (
The method for manufacturing a superconductor according to claim 1, characterized in that at least one of single crystals such as α-Al_2O_3), spinel, strontium titanate, silicon, and gallium arsenide is used. (16) The method for producing a superconductor according to claim 1, wherein porcelain such as alumina, magnesium oxide, zirconium oxide, steatite, forsterite, beryllia, or spinel is used as the substrate. (17) Cu, Ni, Ti, Mo, Nb, Ta on the substrate
2. The method of manufacturing a superconductor according to claim 1, wherein one of metals such as , W, Mn, and Fe, or an alloy containing these metals, such as stainless steel, is used. (18) Claim 1, characterized in that after forming a heat-resistant coating on the surface of the substrate, the composite oxide is attached.
A method for producing a superconductor as described in Section 1. (19) The method for manufacturing a superconductor according to claim 1, wherein the heat-resistant coating is made of a metal oxide, nitride, or carbide. (20) The substrate is Ni, Ti, Mo, Nb, Ta, W,
Claim 1: The substrate is made of at least one type of Mn or an alloy containing these metals, and the surface of the substrate is oxidized, nitrided, or carbonized before the composite oxide is attached. A method for producing a superconductor as described in Section 1. (21) A method for producing a superconductor according to claim 1, characterized in that particles of the composite oxide are mixed at a rate of 5 to 30 g/min into a plasma flame. (22) A plasma flame is generated by applying a voltage between at least a pair of electrodes and using a cathode made of at least one of element A, element B, and Cu. A method for manufacturing superconductors. (23) As the material of the cathode, conductive element A, element B,
The method for manufacturing a superconductor according to claim 1, characterized in that a composite oxide containing Cu is used. (24) The method for manufacturing a superconductor according to claim 1, characterized in that at least one of element A, element B, and Cu is used as the material of the anode. (25) As the material of the anode, conductive element A, element B,
The method for manufacturing a superconductor according to claim 1, characterized in that a composite oxide containing Cu is used. (26) The method for manufacturing a superconductor according to claim 1, characterized in that the substrate temperature is 100°C to 900°C. (27) A method for manufacturing a superconductor according to claim 1, characterized in that the substrate temperature is 200°C to 700°C. (28) Claim 1, characterized in that the composite oxide is formed on the substrate and then heat-treated in an oxidizing atmosphere.
A method for producing a superconductor as described in Section 1. (29) The method for manufacturing a superconductor according to claim 1, characterized in that a plasma flame for heat treatment is used as the method for performing the heat treatment. (30) The superconductor according to claim 5, characterized in that in a plasma flame for plating using at least one type of inert gas, the distance from the anode to the substrate is 3 to 20 cm. manufacturing method. (31) In the plasma flame for plating using at least one type of gas of polyatomic molecules, the distance from the anode to the substrate is set to 10 to 30 cm. Method for manufacturing superconductors.