JP2532986B2 - Oxide superconducting wire and coil using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxide superconducting wire, and more specifically, to an oxide superconducting wire having a current path when an oxide superconductor having a high Jc is quenched. Regarding

[Conventional technology]

Y-Ba-Cu-O layer having a layered perovskite structure,
In the case of Bi-Sr-Ca-Cu-O and Ti-Ba-Ca-Cu-C based oxide superconducting materials, the critical temperature (Tc) is the liquid nitrogen temperature (77).
Since it is above K), it is expected to be widely applied to superconducting magnets, coils or electronic devices.

We have obtained high Jc of the order of 10 ⁶ A / cm ^{2 by the} method of synthesizing oxide superconductors using ceramics single crystal substrate. For example, Applied, Physics, Letters (App
L. Phys. Lett.) 53 (16), 1557 (1988).

Furthermore, other n-type and P-type superconducting wires are already known.

[Problems to be Solved by the Invention]

However, while the oxide superconductor using the ceramic single crystal substrate shown above is relatively easy to obtain a high Jc, in the tape-shaped wire rod of the oxide superconductor, the current when the superconductor is quenched There was a problem in practical use because the pass was not considered.

An object of the present invention is to provide an oxide superconducting wire having a high Jc, which has a current path when the superconductor is quenched, and a coil using the oxide superconducting wire.

[Means for solving the problem]

In order to achieve the above object, in the present invention, an oxide superconductor, a conductive ceramics, and a metal are continuously formed, and a structure having a conductive ceramics sandwiched between the oxide superconductor and the metal, The oxide superconducting wire is characterized in that the conductive ceramic is made of one or more selected from ReO ₃ , TiO and CrO ₂ .

Further, in order to achieve the above object, in the present invention, an oxide superconductor, a conductive ceramics, and a metal are continuously formed, and a recess and / or a recess formed in the longitudinal direction of the conductive ceramics. An oxide characterized in that a metal is continuously formed in the portion, a surface shared by the conductive ceramic and the metal is flat, and an oxide superconductor is formed on the flat substrate surface. In the present invention, a superconducting wire is used, and in the present invention, in a substrate in which a metal is continuously formed in the recess of a ceramic substrate in which a recess is formed in a spiral shape, an oxide superconductor is spread over the metal and the ceramic. An oxide superconducting wire having a disc-shaped coil structure formed in a spiral shape.

In the above, as the conductive ceramics, ReO ₂ ,
It is preferable to use ceramics composed of at least one selected from TiO and CrO ₂ , and those manufactured by the photo-assisted sol-gel method are preferable.

As the ceramic, it is preferable to use one made of at least one selected from MgO, SrTiO ₃ , YSZ, and Ta ₂ O ₃ , and a flexible YSZ tape can also be used.

Further, as the metal that can be used in the present invention, Au,
It is preferable to use at least one selected from Ag, Cu and Ni-Cr alloy (Hastelloy), but other metals can be used as long as they have conductivity and do not react with the superconductor.

The oxide superconducting wire of the present invention becomes an oxide superconducting coil by winding it in a coil shape, and the disc-shaped coils formed in the spiral shape are vertically connected by a superconducting material to form a superconducting coil having a multilayer structure. You can

[Work]

When an oxide superconductor is synthesized on a ceramic MgO (100) or SrTiO ₃ (100) single crystal substrate, a crystal oriented superconductor relatively close to the lattice constant of the substrate can be formed under the influence of the substrate. Further, since the thermal expansion coefficients of the two are close to each other, cracks and the like due to heat treatment can be controlled, and since the reactivity between the ceramic and the superconductor is small, the superconducting property can be improved and high Jc is exhibited.

On the other hand, when a superconductor is directly formed on a metal substrate, a high Jc cannot be obtained because of the generation of cracks due to the difference in thermal expansion coefficient, the high reactivity between the metal and the superconductor, and the non-oriented superconductor. However, the metal substrate has a function as a stabilizing material such as a current path when the superconductor is quenched. Therefore, by forming an oxide superconductor on a substrate in which this ceramic and metal are combined, an oriented high Jc superconductor having a current path when the superconductor is quenched can be formed.

Further, when a conductive ceramic is used as an intermediate between the superconductor and the metal, it functions as suppressing the reaction between the substrate and the superconductor, as an oriented superconducting crystal, and as a current path between the superconductor and the metal. Therefore, when a conductive ceramic is used as the intermediate, a high Jc superconductor can be formed, and further, it functions as a stabilizing material for current paths when the superconductor is quenched.

The method of forming the ceramic film on the metal can be performed by the photo-assisted sol-gel method at low temperature. In addition, a method for forming a ceramic film or a metal film of a ceramic on a metal in a wide temperature range is various ordinary sputtering methods such as a sputtering method, a vapor deposition method, a PVD method such as a laser deposition method, and a chemical vapor deposition method (CVD). It can be performed by a film forming method.

The oxide superconductor is formed on the substrate composed of the metal and the ceramics by the ordinary film forming methods such as the PVD method and the CVD method, the coating technology of the doctor blade method, and the drawing using powder as a starting material. -Can be done by rolling method.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited thereto.

Reference Example 1 A reference example of the present invention is shown in FIG. 1 as a perspective view. First, the Au film 2 is formed to a thickness of 0.1 mm on the side surface of MgO1 by the RF sputtering method.
A thick film was formed to obtain a MgO-Au substrate. Next, by the RF magnetron sputtering method under the conditions shown in Table 1, the Mg
A Y ₁ Ba ₂ Cu ₃ O _{7- δ} oxide superconducting film was formed on an O-Au substrate.

FIG. 2 shows the X-ray diffraction pattern of the minute portion of the formed Y ₁ Ba ₂ Cu ₃ O _{7- δ} oxide superconducting film. In the superconducting film 3 on the MgO substrate, only the diffraction peak based on the (oon) plane is clearly recognized, and it can be seen that the film is C-axis oriented with respect to the substrate surface. Furthermore, it was possible to observe from the SEM image that the reaction layer between the substrate and the superconducting film was 10 nm or less. On the other hand, the superconducting film 4 on the Au substrate can be identified as a non-oriented film because the surface peaks in each direction other than the (oon) peak can be identified. The critical temperature (Tc) at which the resistance of the superconducting film becomes zero and the critical current density (Jc) at 77K were measured by the four-terminal method. The Tc was 87 K and the zero-field Jc was 7.2 × 10 ⁵ A / cm ² . Further, when a voltage was measured before and after the crack when a large current was applied by mechanically introducing a crack into the superconducting film, a voltage corresponding to the resistance of Au could be measured.

As described above, when an oxide superconducting film is formed on a ceramic-metal substrate, a C-axis oriented high Jc film can be formed, and moreover, the metal acts as a stabilizing material for a current path or the like when the superconductor is quenched. it is obvious.

Reference Example 2 SrTiO ₃ , YSZ, and Ta ₂ O ₃ ceramics were deposited with a thickness of 0.25 to 2 mm as a metal by the method shown in Reference Example 1 to obtain a ceramics-Ag substrate. Next, a Y ₁ Ba ₂ Cu ₃ O _{7- δ} superconducting film was formed on the substrate under the conditions shown in Reference Example 1. Superconducting films were formed on both substrates, but SrTiO ₂ -Ag
Best characteristics for substrate, Tc = 87K, Jc at 77K =
8.0 × 10 ⁵ A / cm ² was obtained. The width of the superconducting film is 20 μm.
When the voltage was measured before and after this etching in a state where the superconducting film was completely removed by etching perpendicularly to the longitudinal direction of the substrate, a voltage equivalent to the resistance of Ag could be measured.

As described above, by using the ceramics-metal substrate, high Jc
It is clear that a superconducting film can be formed and that the metal acts as a stabilizing material for current paths and the like.

Example 1 Ni-Cr alloy ReO ₃ to (Hastelloy X) tape, TiO, CrO
_{(2) A} ceramic film was formed with an oxygen partial pressure of 2-3 mtorr to a thickness of about 10 μm by the RF-sputtering method. ReO ₃ , TiO, C
On the Hastelloy X tape with rO ₂ formed, Y ₁ Ba ₂ Cu ₃ O _{7- δ}
The powder was applied by the doctor blade method, heat-treated at 900 ° C. for 5 hours, and then aryl-oxygenated at 450 ° C. for 50 hours to form a superconducting film.

A perspective view of this membrane is shown in FIG. In FIG. 3, 2
Is a Ni-Cu alloy, and 5 is a conductive ceramic. No matter which conductive ceramic was used, it was C-axis oriented and exhibited superconducting properties of Tc> 83K and Jc> 10 ⁴ A / cm ² .
A crack was mechanically introduced into the superconducting film and the ReO ₃ , TiO, and CrO ₂ films, and the voltage was measured before and after the crack, and the voltage corresponding to the resistance of each conductive ceramic and the Hastelloy X resistance could be measured. .

As described above, by forming the conductive ceramics between the metal and the superconductor, a high Jc superconducting film can be formed, and the conductive ceramics can act as an intermediate role as a current path when the superconductor is quenched. it is obvious.

Reference Example 3 Flexible YS molded in a concave shape by extrusion molding
A sol-gel containing Cu alkoxide was poured into the depression on the Z tape, and the sol-gel was decomposed and crystallized by irradiating it with ultraviolet rays from a mercury lamp to form a Cu film at a low temperature of 200 ° C. The YSZ-Cu surface was polished and flattened to obtain a substrate. Bi _1.8 (Pb _0.4 ) Sr ₂ Ca ₂ Cu ₃ Ox was formed on the substrate heated to 700 ° C. by laser debossing and then annealed at 845 ° C. for 50 hours in the atmosphere to obtain a superconducting film.

A perspective view of this membrane is shown in FIG. In FIG. 4, 1
The YSZ tape, the Su film, the superconducting film of 3, and the superconducting film of 3 were C-axis oriented, and Tc was 108K and Jc was 1.2 × 10 ⁵ A / cm ² . Also, C
When a voltage was measured by introducing cracks in the superconducting film on the u surface by the method shown in Reference Example 1, the voltage corresponding to the resistance of Cu could be measured.

As described above, it is clear that by using the YSZ-Cu substrate having the above-described shape, a C-axis oriented high Lc superconducting film can be formed, and Cu acts as a current path when the superconductor is quenched.

Example 2 An Mg film having a thickness of 0.5 μm was formed by RF sputtering on a Si wafer. A spiral pattern having a width of 1 mm was used to irradiate the entire wafer with laser light, and the MgO film was etched along the pattern shape to perform pattern molding. Next, using the above pattern, an Ag film was formed by RF sputtering until it had the same thickness as the MgO film. Using a spiral pattern having a width of 3 mm on the MgO-Ag-Si substrate, Y ₁ was formed under the conditions shown in Reference Example _1.
A Ba ₂ Cu ₃ O _{7- δ} film was formed.

A sectional view of the structure of this film is shown in FIG. In FIG. 5, 1 is MgO, 2 is Ag, and 6 is a superconducting film. The superconducting characteristics by the four-terminal method are Tc = 84K, Jc = 1.4 × 10 ⁴ A / cm ² (77
K, 0T). Further, when a voltage was measured before and after the etching after etching a part of the superconducting film with an electron beam, a voltage corresponding to the resistance of Ag was measured.

As described above, it is clear that by using the spiral Ag film, a relatively high Jc superconducting film can be formed, and Ag acts as a current path when the superconductor is quenched.

Example 3 A multilayer disc-shaped coil can be formed by connecting with the superconducting film 6 at the end of the spiral-shaped superconducting film obtained in Example 2 and stacking them in multiple layers to form the structure shown in FIG. The magnetic field of 77K in the disk coil generated 1.0T. A tape coil was prepared by winding the superconducting tape obtained in Example 1 around a conductor, and a magnetic field of 77K was generated at 0.9T.

〔The invention's effect〕

According to the present invention, by forming the oxide superconductor over both the ceramic and the metal, the reaction between the ceramic and the superconductor can be suppressed, and further, C
Since an axially oriented superconductor could be formed, high Jc at 77K, 0T
was gotten. Further, since the superconductor is made of metal, the metal has an effect of acting as a current path when the superconductor is quenched. Further, by using the conductive ceramics between the metal and the superconductor, the reaction between the ceramics and the superconductor was suppressed, and due to the C-axis oriented film, a high Jc was obtained at 77K, 0T. Further, when the superconductor is quenched, an electric current can flow to the metal through the conductive ceramics, which has an effect of acting as a stabilizing material.

As described above, a superconductor with high Jc can be formed, and since it functions as a current path when the superconductor is quenched, it has an effect of being applicable to a wire rod such as a superconducting coil.

[Brief description of drawings]

FIG. 1 is a perspective view of the superconducting wire of Reference Example 1, and FIG.
FIG. 3 is an X-ray diffraction pattern diagram of the superconducting film formed on the MgO and Au plates of Reference Example 1, and FIG. 3 is a perspective view of the superconducting wire having conductive ceramics between the superconductor and the metal of the present invention.
FIG. 5 is a perspective view of a superconducting wire of Reference Example 3, FIG. 5 is a schematic view in which a superconductor is formed on a ceramic plate in which the metal of the present invention is formed into a spiral shape, and FIG. 6 is a multilayer disc of the present invention. It is a schematic diagram of a spiral coil. 1 ... Ceramics, 2 ... Metal, 3 ... C-axis oriented superconducting film, 4 ... Non-oriented superconducting film, 5 ... Conductive ceramics, 6 ... Superconducting film, 7 ... Si wafer

Claims (5)

(57) [Claims] 1. An oxide superconductor, a conductive ceramic, and a metal are continuously formed, and the oxide superconductor and the metal have a structure in which the conductive ceramic is sandwiched between the oxide superconductor and the metal.
An oxide superconducting wire characterized in that the conductive ceramic is made of one or more selected from ReO ₃ , TiO, and CrO ₂ . 2. A recess and / or a recess formed in the longitudinal direction of the conductive ceramic in which an oxide superconductor, a conductive ceramic and a metal are continuously formed. An oxide superconductor is formed by continuously forming a metal on the surface of the conductive ceramics, a surface shared by the conductive ceramics and the metal is flat, and an oxide superconductor is formed on the flat substrate surface. wire. 3. The oxide superconducting wire according to claim 1 or 2, wherein the conductive ceramic is manufactured by a photo-assisted sol-gel method. 4. A ceramic substrate in which a recess is formed in a spiral shape, in which a metal is continuously formed in the recess, and a disk shape in which an oxide superconductor is formed in a spiral shape across the metal and the ceramic. An oxide superconducting wire having a coil structure. 5. An oxide superconducting coil, wherein the disk-shaped coils of the oxide superconducting wire according to claim 4 are vertically connected by a superconducting material to form a multilayer structure.