JPS63239738A - Superconductor wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To secure such a superconductor wire that is homogeneous and excellent in accuracy as compared with the conventional sintered body securable by installing a coat with a specific main constituent, on a string or ribbonlike substrate. CONSTITUTION:A layer structure, where a ternary compound superconductive coat 12 of a Y-Ba-Cu-O system, that is, (A, B)3Cu2O7 in a base is stuck, is formed on the surface 13 of a string or ribbonlike substrate 11. Here, a shows at least one type of Sc, Y and lanthanum elements (atomic number 57-71) and B shows at least one type of elements of groups IIa such as Ba, Sr, Ca, Be, Mg, etc. In this manner, it comes to well homogeneity as compared with the conventional sintered body, thus a highly accurate superconductor wire is securable.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a superconductor wire and a method for manufacturing the same. In particular, it relates to compound thin film superconductor wires.

Conventional technology As a high temperature superconductor, niobium nitride (NbN) and germanium niobium (Nb3G) are used as A15 type two-element compounds.
e), etc., but the superconducting transition temperature of these materials was at most 24°. On the other hand, perovskite-based ternary compounds are expected to have even higher transition temperatures, and Ba-La-Cu-0-based high-temperature superconductors have been proposed [J, G, Bend.

rz and K, A, Moller, Zeitschrif
t f ar Physik, )-Condens
ed Matter 64.189-193 (198
6) ]. Furthermore, ]Y-Ba-Cu-0 was recently proposed to be a higher temperature superconducting material. [F4.
K, WnM.

K, Wn, etc., Physical Reputation Letters (Phys
icat Review Letters) Vol.
58. No9.908-910 (198Y-Ba-
Although the details of the superconducting mechanism of Cu-0-based materials are not clear, the transition temperature may be higher than the liquid nitrogen temperature, and as a high-temperature superconductor, it is expected to have more promising properties than conventional two-element compounds. Y-Ba-Cu-0 based materials can only be formed through the process of sintering with current technology, so they can only be obtained in the form of ceramic powder or blocks. On the other hand, when this type of material is put to practical use, there is a strong demand for processing it into a linear or thin film shape, but this type of processing has been considered extremely difficult with conventional techniques.

The present inventors have discovered that a thin film-like high-temperature superconductor is formed when a thin film of this type of material is deposited by an ion process, and based on this discovery, a novel method for manufacturing superconductor wire has been discovered. .

Means for Solving the Problems The basic structure of the superconductor wire of the present invention is that Y-Ba-Cu is coated on the surface of a linear or ribbon-like substrate.
-0 system, that is, the main component is (A.

B) It is characterized by a layered structure to which a ternary compound superconducting film of 3 cugoy is attached. The present inventors have proposed that such a layered superconductor wire can be produced by depositing a 3Cu207 composite compound film of the main components (A, B) on a linear or ribbon-like substrate, for example, by a process called vapor deposition, and then heat-treating it in an oxidizing atmosphere. They found that it is formed by Here, A is Sc, Y, and lanthanum series elements (atomic number 57-
71), B is Ba, S r, Ca
, Be, Mg, and other elements of the na group.

Function: The superconductor wire produced by the method of the present invention has a major feature in that the superconductor is made into a thin film. In other words, because film thinning involves decomposing the superconductor material into ultrafine particles in the atomic state and then depositing them on the substrate, the composition of the formed superconductor wire is essentially more homogeneous than that of conventional sintered bodies. be. Therefore, a superconductor wire of very high precision is realized with the present invention.

Example A method according to an embodiment of the present invention will be explained with reference to the drawings.

As shown in FIG.
It is formed on the surface 13 by, for example, a sputtering method. In this case, the base 11 has a ternary compound coating 12 exhibiting superconductivity.
The purpose is to maintain the The superconductor of the present invention essentially consists of such a layered structure. This layered structure is usually formed at a high temperature of several hundred degrees Celsius, and since superconductors are operated at a low temperature of, for example, liquid nitrogen temperature (-195 degrees Celsius), the adhesion between the substrate 11 and the coating 12 is particularly poor (and the layered structure is often formed). The inventors have confirmed that the substrate is damaged.Furthermore, the inventors investigated the detailed thermal characteristics of the substrate for various materials, and found that the linear thermal expansion coefficient α>lQ-8/ If this quartz glass is used as a substrate, the layered structure will not be damaged (and it has been confirmed that it can be put into practical use.For example, α〈10-67) If this quartz glass is used as a substrate, the coating 12 will have countless cracks and become a discontinuous coating. The inventors have confirmed that this method is not practical.

Furthermore, the present inventors have discovered that there is an optimal material for the layered structure substrate 11 shown in FIG. 1 from the viewpoint of functionality.

That is, the base body 11 is made of Cu, Ni, or Ti.

The present inventors have confirmed that metals such as Mo+ Ta, W, Mn+ Fe-, or alloys containing these metal elements, such as nichrome and stainless steel, are effective. In this case, since this type of substrate is processed into a linear or ribbon shape, a superconductor wire is formed by attaching the superconductor coating 12 to the surface of the linear or ribbon-shaped substrate. FIGS. 2(a) and 2(b) show a superconductor wire according to an embodiment of the present invention, in which a superconductor coating 12 is formed on the surfaces of a ribbon-like substrate 11A and a linear substrate 11B.

To form a superconductor wire, first (A, B) sCuz07-
A composite compound film of component J is deposited on the substrate by a physical vapor deposition method such as sputtering vapor deposition.

Here, O≦δ≦7°. In this case, the composite compound film only needs to match the stoichiometric ratio of components A, B, and CU, and the present inventors have confirmed that the amount of oxygen is not particularly important. As a result, methods for forming composite compound films are not limited to physical vapor deposition (e.g., atmospheric or low pressure chemical vapor deposition, plasma chemical vapor deposition). The present inventors have confirmed that the photochemical vapor deposition method is also effective as long as the stoichiometric ratios of components A, B, and Cu match.

The present inventors have proposed that when attaching a composite compound film to the surface 13 of the substrate 11, as shown in FIG. It has been found that self-heating by heat generation is particularly effective for manufacturing this type of superconductor wire.

In this case, the present inventors have confirmed that there is an optimal temperature range due to self-heating of the substrate. That is, the optimum temperature range of the substrate is 100 to 1000°C. In addition, 10
At temperatures below 0°C, the adhesion of the composite compound coating to the substrate surface deteriorates. In addition, the inventors have found that at temperatures above 1000°C, the deviation from the stoichiometric ratio of components A, B, and Cu in the composite compound film becomes large, and superconducting properties cannot be obtained even after subsequent heat treatment steps. discovered.

Furthermore, the present inventors have found that a temperature range of 200 to 500°C for the substrate when depositing the composite compound film is optimal in terms of the functionality of this type of vapor deposition apparatus and the reproducibility of the properties of the composite compound film. confirmed. In this case, the formed composite compound film is amorphous or superconducting (A, B) 3Cu z O? It is composed of microcrystals such as. However, surprisingly, this type of coating exhibits semiconducting properties and superconductivity is often not observed even at liquid He temperatures (4°K).

The present inventors have discovered that superconductivity can be generated by further heat-treating this type of composite compound film in an oxide atmosphere such as air at normal pressure, a mixed gas of argon and oxygen, or pure oxygen. In this case, the optimal heat treatment temperature is 900
~1000°C, heat treatment time is 10 to 100 hours,
In particular, it is characterized by a long heat treatment time, which is unconventional for thin film materials, and by slow cooling after heat treatment. Heat treatment time: 10
If the cooling time is less than 100 hours, there will be many semiconductor-like characteristics, and the reproducibility will deteriorate (superconducting characteristics will not be obtained).If the cooling time is longer than 100 hours, the resistivity will increase and the properties of the film will become unstable, and quenching will not show superconductivity. For example, an annealing time of 20 hours or more is required to obtain superconductivity.

In the process of forming this type of superconducting sintered body, a long heat treatment of 10 to 100 hours, similar to the heat treatment used in the present invention, is used. However, in the case of a bulk material such as a sintered body, a heat treatment time of about 100 hours, for example, is not particularly long and is usually widely used. On the other hand, in the case of a film, the dimensions of the material itself are, for example, 1 μm.
This is three to four orders of magnitude smaller than the bulk where m is less than that. Therefore, the heat treatment time is also less than two orders of magnitude shorter than that of bulk materials when considering the movement of substances.Therefore, if the heat treatment process is similar to that of bulk materials, superconducting properties should be obtained with a short heat treatment of one hour or less. Furthermore, it was thought that this type of heat treatment would be unnecessary if an oxidizing atmosphere was used during film formation.However, it was experimentally confirmed that a long heat treatment was required as described above.This unexpectedness This is thought to be due to the essential difference in properties between the bulk material and the thin film material.

That is, the detailed characteristics of this type of coating, such as the crystal structure, are such that because the coating is constrained on the substrate, there are large strains and defects in the coating that do not exist in ordinary sintered bodies. Therefore, the conventional method for manufacturing a sintered body cannot be directly applied to the method for manufacturing the coating. Furthermore, it is not possible to infer the method of manufacturing the coating from the method of manufacturing the sintered body. Although the details of the physical meaning of the heat treatment of the film are not clear, it can be roughly considered as follows. That is, the compound 3CI4207 (A, B) is not formed in the composite oxide film deposited on the substrate by sputtering vapor deposition or the like. In this case, for example, BCuOs
A complex oxide is formed in which the oxide of the element is dispersed in a network of a tetragonal perovskite structure. Superconductivity results from the development of a layered herovskite structure, a process that is associated with heat treatment.

Note that the reason why superconductivity was not obtained when the heat treatment time was 10 hours or less is considered to be due to insufficient formation of the layered perovskite structure.

When forming a composite compound film on the surface of a substrate by sputtering deposition, it is important to control the stoichiometric ratio of components A, B, and Cu in the film, as described above. We investigated the conditions, and surprisingly found that the composition of the sputtering target could be sCuzo7-a, whose main components are the same as the target superconductor (A, B). Here, O≦δ≦7, and oxygen The amount can be adjusted by heat treatment during or after sputtering, so it is particularly important for the target composition.

Furthermore, in sputtering deposition of this type of compound film, a mixed gas of Ar and ○Z is used as the sputtering gas, but the presence of 02 gas increases the resistivity of the formed compound film and prevents the formation of a superconductor. The present inventors have found that there are cases where this is necessary. Experimentally, Ar, Xe, Ne
The present inventors have confirmed that an inert gas such as , Kr, or a mixed gas of these inert gases is effective as a sputtering gas.

The present inventors have confirmed that all sputtering vapor deposition methods, such as high-frequency bipolar sputtering, direct current bipolar sputtering, and magnetron sputtering, are effective.

Particularly in the case of DC sputtering, it is necessary to lower the resistivity of the sputtering target to below 10-3 Ωam; if the resistivity is higher than this, sufficient sputtering discharge will not occur. Note that the target resistivity is usually adjusted. This is done depending on the target sintering conditions.

FIG. 3 shows the structure of a substrate when a composite oxide film is formed on a linear or ribbon-shaped substrate by this type of sputtering deposition method. As shown in the figure, a plurality of targets 21
．． 22, and a complex oxide film is uniformly adhered to the surface of a linear 23 or ribbon 24 substrate. For example, ribbon substrate 24 may be coated simultaneously on surface 252 and surface 26 to prevent mechanical deformation of the ribbon substrate.

Note that active adjustment of the chemical composition of the film and the formation of artificial chemical composition fluctuations such as an artificial lattice are made possible by multi-source sputtering. Particularly in this type of apparatus, the present inventors have confirmed that DC sputtering is effective for precise control of sputtering power, etc., and that DC magnetron sputtering or a DC magnetron sputter gun is particularly effective.

In addition, as a method for forming a composite compound film on the surface of a substrate, the main component of the metal is deposited on the substrate by physical vapor deposition, and the film is further irradiated with an oxygen beam or oxygen ions during film formation. It is also possible to oxidize the main component. In addition to sputtering, thermal evaporation, such as electron beam evaporation, is also effective as a physical vapor deposition method. In the sputtering method, while irradiating the substrate with an oxygen ion beam, the main alloy component of the composite oxide film is sputter-deposited using a target. In this case, the film formation rate is more than an order of magnitude faster than sputtering vapor deposition using a composite oxide target, and it is industrially more effective.

Furthermore, the present inventors have found that, before forming a complex oxide film on the surface of a linear or ribbon-shaped substrate, if a heat-resistant coating is previously formed on the surface of the substrate, for example, on the surface of a metal substrate, stable superconductivity can be achieved. I discovered that it is possible to achieve this.

FIG. 4 is an X-ray diffraction spectrum diagram showing the results of the heat-resistant coating. The substrate is made of Mo metal and a heat-resistant film is deposited using tantalum oxide O, lμliG sputtering method. Characteristic a in the figure shows the property when there is no heat-resistant coating, property C shows the property when there is a heat-resistant film, and property C shows the property of the layered perovskite structure exhibiting superconducting properties.

As can be seen from the figure, when a heat-resistant coating is provided, it exhibits characteristics similar to those of a layered perovskite structure, but when there is no heat-resistant coating, there is a difference in the X-ray diffraction spectrum. The details of this reason are not clear, but
This is thought to be due to interlayer diffusion between the base metal and the composite compound film during the deposition of the composite oxide film.

The heat-resistant coating may be formed by the vapor deposition method described above, or by chemically modifying the surface of the base metal. For example, the same effect can be obtained by oxidizing, nitriding or carbonizing the base metal surface in an oxidizing, nitriding or carbonizing atmosphere to form an oxide, nitride or carbide film of the base metal on the base metal surface.

Furthermore, when a metal such as tantalum or titanium is used for the substrate, it is also possible to oxidize the surface by a so-called anodization method.

Examples of nitrides used as the heat-resistant coating include TiN.

TaN, MoN, NbN, WN, MnN, etc., and carbides include TaC, 'ric, NbC, M.

C, WC, MnC, etc., but N b 20 as an oxide
s, T i OI! , Ta2'5. AI 20
3. The present inventors have confirmed that Z r O, 21Y 20 a, etc. are effective.

The effect of these heat-resistant coatings is to stabilize the composite compound coating during high-temperature processing, so it is only necessary that heat resistance and adhesion to the substrate be satisfied, so they are not limited to the materials mentioned above. do not have. However, from the viewpoint of adhesion properties, heat-resistant coatings formed by surface reactions of base metals, such as Ta/Tag's,
Ti/TiO2 etc. are effective.

In addition, from the viewpoint of heat resistance, if the base metal has good heat resistance, a heat-resistant coating is not necessarily required. For example, the present inventors have confirmed that this type of superconducting film can be stably formed on stainless steel metal even without a heat-resistant film.

In order to further understand the contents of the present invention, more specific examples will be shown below.

(Specific Example) Using the tantalum ribbon 11A shown in FIG. 2(b) [width 10 mm, thickness 0.1 mm+1] as a base, first, a tantalum oxide heat-resistant layer is formed on the surface of the tantalum ribbon 11A by high-frequency Brenner magnetron sputtering. Furthermore, a sintered (Y,Ba)3cugo7 target was sputter-deposited on the substrate by sputtering in an Ar gas atmosphere using high-frequency planar magnetron sputtering.
Y, Ba)3Cu207 coating 12 was deposited to form a layered structure. In this case, the pressure of Ar gas is 0.5 Pa
, sputtering power 150W, sputtering time 1
0 hours, the film thickness of the film was 6 μm, and the substrate temperature was 250°C. The formed layered structure was further heated in air at 900°C and 70°C.
Heat treated for hours. The superconducting transition temperature was 45°K.

This type of ternary compound superconductor (A + B) s C
The details of changes in superconducting properties due to changes in constituent elements A and B of ti 207 are not clear. However, A is trivalent, B
is 2g! It is true that it shows 4. Although the explanation was given using Y as an example, Sc, La, and even lanthanum series elements (atomic numbers 57 to 71) can change the essential characteristics of the layered structure of the invention to the extent that the superconducting transition temperature changes. It's not a thing.

Also, regarding B elements, changes in group 11a elements such as Sr, Ca, and Ba change the superconducting transition temperature by about 10°, but this does not essentially change the characteristics of the layered structure of the present invention.

The superconducting material shown here has a two-layer perovskite structure, but this type of perovskite-structure superconducting material (A, B) h-++Cuno3n++ has a multilayer (0-layer) structure such as a three-layer structure or a four-layer structure. can also be formed by the same manufacturing method as the present invention, and can be put to practical use as a superconducting material.

Effects of the Invention The method for manufacturing a superconductor wire according to the present invention is characterized in that the superconductor is made into a thin film. In other words, in thin film formation, the superconductor material is decomposed into ultrafine particles in the atomic state and then deposited on the substrate, so the composition of the formed superconductor is essentially more homogeneous than that of conventional sintered bodies. be. Therefore, a superconductor wire with very high precision is realized with the present invention.

In particular, the transition temperature of this type of compound superconductor may be room temperature, so the range of conventional practical use is wide (and the industrial value of the present invention is high).

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a basic configuration diagram of a superconductor wire formed by a method for manufacturing a superconductor wire according to an embodiment of the present invention, and FIG. 3 is a diagram for explaining the present invention in detail. FIG. 4 is a basic configuration diagram of a superconductor wire manufacturing apparatus and a basic characteristic diagram of the superconductor wire of the present invention. 11...Substrate, 12...Ternary compound coating. Name of agent: Patent attorney Toshio Nakao 1st person / 11th Toru 1r Figure 2

Claims (21)

[Claims] (1) On a linear or ribbon-like substrate, the main components (A,
B) A superconductor wire characterized by being provided with a coating of _3Cu_2O_7. Here, A represents at least one kind of Sc, Y, and lanthanum series elements (atomic numbers 57 to 71), and B represents at least one kind of group IIa elements. (2) The superconductor wire according to claim 1, characterized in that a heat-resistant coating is provided on the base. (3) On a linear or ribbon-shaped substrate, the main component is AB_
A method for producing a superconductor wire, which comprises depositing a composite compound film of 2Cu_3O_7_-_δ and further heat-treating in an oxidizing atmosphere. Here, A represents at least one kind of Sc, Y, and lanthanum series elements (atomic numbers 57 to 71), and B represents at least one kind of group IIa elements. Also, 0≦δ
≦7. (4) The method for manufacturing a superconductor wire according to claim 3, characterized in that the substrate is made of a material having a coefficient of linear expansion α>10^-^6/°C. (5) The substrate is Cu, Ni, Ti, Mo, Nb, Ta,
4. The method of manufacturing a superconductor wire according to claim 3, wherein the superconductor wire is made of one of metals such as W, Mn, and Fe, or an alloy containing these metals, such as stainless steel. (6) The method for manufacturing a superconductor wire according to claim 3, characterized in that after forming a heat-resistant coating on the surface of a linear or ribbon-shaped substrate, a composite compound coating is attached. (7) The method for manufacturing a superconductor wire according to claim 6, wherein the heat-resistant coating is made of a metal oxide, nitride, or carbide. (8) The substrate is made of linear or ribbon-like Ni, Ti, Mo,
The substrate is made of at least one of Nb, Ta, W, and Mn, or an alloy containing these metals, and each of these metals on the surface of the substrate is oxidized and nitrided before the composite compound film is attached. Or oxidize the substrate surface in a carbonizing atmosphere.
7. The method for producing a superconductor wire according to item 6, which comprises nitriding or carbonizing the superconductor wire. (9) The method for producing a superconductor wire according to claim 3, characterized in that the composite compound film is deposited on a gas by a physical vapor deposition method such as sputtering vapor deposition or thermal vapor deposition. (10) The composite compound coating is deposited on the substrate by a chemical vapor deposition method such as normal pressure or reduced pressure chemical vapor deposition method, plasma chemical vapor deposition method, or photochemical vapor deposition method. A method for manufacturing a superconductor wire according to claim 3. (11) Regarding the attachment of a composite compound coating onto a substrate, a patent characterized in that a linear or ribbon-shaped substrate is made of a conductive material, and the coating is attached by generating heat and self-heating by passing an electric current through the substrate. A method for manufacturing a superconductor wire according to claim 3. (12) Regarding the attachment of the composite compound coating onto the heated substrate,
4. The method of manufacturing a superconductor wire according to claim 3, wherein the substrate is heated to a temperature in the range of 100 to 1000°C. (13) Regarding the attachment of the composite compound coating onto the heated substrate,
4. The method for manufacturing a superconductor wire according to claim 3, wherein the substrate is heated within a range of 200 to 500°C. (14) The method for manufacturing a superconductor wire according to claim 3, characterized in that atmospheric pressure air or pure oxygen is used as the atmosphere. (15) In sputtering deposition, the main components are (A, B
10. The method for manufacturing a superconductor wire according to claim 9, characterized in that a composite compound target of )_3Cu_2O_7_-_δ is sputter-deposited. 0 here
≦δ≦7. (16) In sputtering deposition, Ar, Xe, N
16. The method for manufacturing a superconductor wire according to claim 15, characterized in that sputtering is performed using at least one of E, Kr, or a mixed gas thereof. (17) The method for producing a superconductor wire according to claim 9, wherein the sputtering vapor deposition is performed by at least one type of high-frequency dipole sputtering. (18) The method for producing a superconductor wire according to claim 9, wherein the sputtering vapor deposition is performed by simultaneously sputtering a plurality of targets. (19) The electrical resistivity of the composite compound target is 10^-
The method for manufacturing a superconductor wire according to claim 9, characterized in that the resistance is 3 Ωcm or less. (20) In the physical vapor deposition method, the main metal component of the composite compound film is deposited on the substrate, and then oxygen beam or oxygen ions are irradiated during film formation to oxidize the main metal component on the surface of the substrate. A method for manufacturing a superconductor wire according to claim 9. (21) In the physical vapor deposition method, the superconductor according to claim 9, wherein the main alloy component of the composite compound film is sputter-deposited while irradiating the substrate with an oxygen ion beam. Method of manufacturing body lines.