JPH01162304A - Oxide superconducting coil - Google Patents

Abstract

PURPOSE:To prevent the deterioration in superconducting characteristics caused by the mechanical stress generated when a winding work is conducted and to sharply reduce the irregularity in manufactured articles by a method wherein an oxide superconducting body and an electric insulator consisting of ceramic are closely fixed, and they are formed into a spiral form by winding them alternately. CONSTITUTION:An oxide superconducting material 2 and an electric insulator 3, made of the ceramic shown by a general formula Ln2MCuO5, are closely adhered and the title coil is formed in spiral form in which they are wound alternately. The Ln in the formula is at least a kind of element selected from La, Sc, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and the M is at least a kind of element selected from bivalent alkaline earth metals. The superconducting material 2 is a perovskite type oxide superconducting material containing a rare-earth element. As a result, the deterioration in superconducting characteristics caused by the mechanical stress generated when a winding work is conducted can be prevented, and the irregularity of manufactured articles can also be reduced sharply.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a superconducting coil obtained using an oxide superconductor without requiring a winding process.

(Prior Art) In recent years, it has been announced that layered perovskite-type oxides based on Ba-La-Cu-0 may have a high critical temperature, and since then, research on oxide superconductors has been carried out in various places. (Z, Phys, B Condensed Mat
ter64, 189-193 (1986)). Among them, defective perovskite type ([nBa2Cu307-δ type,
δ represents an oxygen defect and is usually 1J:1. Bottom, [n is Y,
La; Sc, Nd, Sm, Eu, Gd, D
Oxide superconductors of at least one element selected from y, No, Er, Tm, Yb, and Lu (some of the Ba can be replaced with nails, etc.) have a critical temperature of 90 or higher and a temperature higher than that of liquid nitrogen. It is attracting attention as a very promising material because it exhibits high temperatures (Phys, 'Rev, Lett,
Vol. 58 No. 9.908-910).

By the way, various types of coils have been studied for alloy-based or intermetallic compound-based superconductors, and they have already been put to practical use in NMR and rotating electric machines, but the oxide superconductors mentioned above are brittle crystalline oxide Since it is a material with poor flexibility, it is difficult to obtain a wire or tape with good flexibility.

In addition, this oxide superconductor is weak against mechanical stress,
If the wire is distorted beyond a certain value, the superconducting properties will deteriorate or disappear, making it difficult to obtain a desired current density when winding the wire, making it extremely difficult to apply it to coils.

(Problems to be Solved by the Invention) As described above, it is difficult to obtain a wire with excellent flexibility using an oxide superconductor and to obtain a desired current density during winding. Manufacturing coils using physical superconductors has been extremely difficult.

The present invention has been made to solve these conventional problems, and an object of the present invention is to provide an oxide superconducting coil that can be obtained using an oxide superconductor without requiring a winding process.

[Structure of the Invention] (Means for Solving the Problems) That is, the oxide superconducting coil of the present invention includes an oxide superconductor, -bottom Ln2MCuO,, (Ln is YlLa
, Sc, Nd, Sm, Eu, Gd, Dy,
An electrical insulator made of ceramics represented by at least one element selected from Ho, Er, Tm, Yb and Lu, H being at least one element selected from divalent alkaline earth metals. It is characterized by being formed in close contact and alternately in a spiral shape.

Although various oxide superconductors can be used in the present invention, the use of a perovskite-type oxide superconductor containing a rare earth element, which has a high critical temperature, has a particularly large practical effect.

The oxide superconductor containing a rare earth element and having a velorskite structure may be one that can realize a superconducting state, and may be of the LnBa2 Cu307-δ system (δ represents an oxygen defect and is usually a number of 1 or less, Ln is Y, La,
5cSNd, Sm, Eu, Gd, Dy, Ho
, ErSTm.

At least one element selected from Yb and Lu, B
Examples include oxides having a perovskite type in a broad sense, such as a defective perovskite type having oxygen vacancies such as (part of a can be replaced with Sr etc.), and a layered velourskite type such as 5r-La-Cu-0 system. . Rare earth elements are also broadly defined to include Sc1'f and La-based elements. In addition to the Y-Ba-Cu-0 system, representative systems include Y for Eu,
Dy, Ho, Er, Tm, Yb, system substituted with rare earth elements such as Lu, 5c-Ba-Cu-0 system, 5r-L
Examples include the a-Cu-0 system and systems in which Sr is replaced with Ba or Ca.

The oxide superconductor used in the present invention is manufactured, for example, as shown below.

First, the constituent elements of the perovskite oxide superconductor, such as Y, Ba, and Cu, are thoroughly mixed. When mixing, Y
Oxides such as 2O3, [u203, CuO, etc. can be used as raw materials. In addition, compounds such as carbonates, nitrates, hydroxides, etc., which are converted into oxides after firing, may be used in these materials. Furthermore, oxalate obtained by a coprecipitation method or the like may be used. The elements constituting the perovskite-type oxide superconductor are basically mixed so as to have a stoichiometric composition, but there is no problem even if the composition deviates slightly depending on the manufacturing conditions. For example, in the Y-Ba-Cu-0 system, Y 1
The standard composition is Ba 2 mol and Cu 3 mol per mol, but in practice, Ba 2 mol and Cu 3 mol are
A deviation of about 2±0.6 mol and Cu 3±0.2 mol is not a problem.

After mixing the above-mentioned raw materials, they are calcined and pulverized into a desired shape, and then fired at about 850 to 980°C. Calcining is not necessarily necessary. Preferably, calcination and firing are performed in an oxygen-containing atmosphere where sufficient oxygen can be supplied. After firing into a desired shape, it is heat-treated in an oxygen-containing atmosphere to improve superconducting properties. This heat treatment is usually 600
Do this while slowly cooling below ℃.

The oxide superconductor thus obtained has oxygen defects δ
Oxygen-deficient perovskite structure (LnBa2
Cu307-6, δ is usually 1 or less).

Note that Ba can also be replaced with at least one of Sr and Ca, and roughly a part of Cu can be replaced with Ti1V, Cr,
Hn, Fe.

It can also be replaced with C01H+, zn, etc.

The amount of this substitution can be set as appropriate within a range that does not reduce the superconducting properties, but too much substitution will reduce the superconducting properties, so it should be limited to 80mo 1% or less, and more practically 20mo 1% or less. .

In addition, the electrical insulators used in the present invention include -ship bottom n
21 (CIJO5 (Ln is Y, La, Sc,
Nd, 8m, Eu.

Ceramics represented by at least one element selected from GdXDV, HOlEr, Tm, Yb, and Lu, where H is at least one element selected from divalent alkaline earth metals are preferred. This makes it possible to almost match the shrinkage of the oxide superconductor during firing with the shrinkage of the above-mentioned ceramics, and further reduces the effect on properties due to mutual diffusion between the oxide superconductor and the electrical insulator during firing. Therefore, by using this ceramic as an electrical insulator, cracks and distortions that occur on the bonding surface due to differences in shrinkage rate during manufacturing can be suppressed, and the superconducting properties of oxide superconductors and coils can be reduced. This is because it is possible to prevent a decrease in mechanical strength.

This electrical insulator uses the same material as the material for the oxide superconductor described above as a starting material, mixes each starting material to have a stoichiometric composition, and then shapes it into a desired shape.
It can be obtained by firing at about 00 to 950°C.

The oxide superconducting coil of the present invention uses the above-mentioned materials, and
For example, it can be manufactured by the following method.

(2) First, the oxide superconductor obtained by firing is pulverized by a known means such as a ball mill to obtain an oxide superconductor powder. A binder and a plasticizer are added to this oxide superconductor powder and mixed to form a mixture.

Also, a mixture of electrical insulators is obtained in the same manner.

Next, as shown in FIG. 3, each of the obtained mixtures is linearly extruded separately using one or two extruders 31, and then, while still having plasticity, an oxide superconductor 32 and an electrical insulator are extruded. 33 are arranged alternately, and wound onto a cylindrical drum 34.

After this, the molded product is heat-treated at 400 to 500°C to volatilize the organic components, and then heated to 850 to 980°C in an oxygen-containing atmosphere.
The oxide superconductor is fired at 100° C. and then slowly cooled to 600° C. or lower to introduce oxygen into the oxygen vacancies in the crystal structure of the oxide superconductor to obtain an oxide superconducting coil.

■After extruding the oxide superconductor and the electric insulator separately in a straight line in the same manner as in ■■, as shown in FIG. The oxide superconductor 43 and the electrical insulator 44 are separately rolled by two conical rolls 42 arranged close to each other with their circumferential surfaces along the longitudinal direction to form a spiral laminate 45.
get.

Thereafter, the laminate is subjected to the same heat treatment as in (1) to obtain an oxide superconducting coil.

■ When extruding the oxide superconductor and the electrical insulator separately in the same way as in ■, the pressure applied to the extruder nozzle is made different across the center of the nozzle, so that the oxide superconductor and the electrical insulator are extruded separately. A spiral laminate is obtained by alternating positions.

Thereafter, the laminate is subjected to the same heat treatment as in (1) to obtain an oxide superconducting coil.

■ First, obtain oxide superconductor powder in the same manner as in ■, add a solvent, a binder, and if necessary a plasticizer or peptizer to this oxide superconductor powder, then mix and heat-treat. , obtain green sheets of oxide superconductor.

Further, a green sheet of electrical insulator is obtained in the same manner.

These green sheets were used instead of extruded materials and formed into a spiral shape so that oxide superconductors and electrical insulators were arranged alternately, and then heated at 850°C to 850°C in an oxygen-containing atmosphere.
Calcining at 980°C, then slowly cooling below 600°C to introduce oxygen into the oxygen vacancies in the crystal structure of the oxide superconductor,
Obtain an oxide superconducting coil.

Note that the shape of the oxide superconductor and the shape of the electrical insulator constituting the oxide superconducting coil of the present invention do not need to be the same, and the shape of the electrical insulator can completely insulate between the oxide superconductors. It can be of any shape as long as it is of any shape. In addition, to improve the mechanical strength of the coil,
The entire oxide superconducting coil of the present invention may be coated with an electrically insulating resin such as epoxy resin.

(Function) The oxide superconducting coil of the present invention is obtained by alternately forming extruded products or green sheets of oxide superconductors and electrical insulators into a spiral shape, and then subjecting them to heat treatment. There is no need to convert superconductors and insulators into wires. Therefore, since a winding process is not required, there is no deterioration in superconducting properties due to winding.

Furthermore, since the difference in shrinkage rate between the oxide superconductor and the electrical insulator is small, it is possible to prevent cracks and distortions at the bonding surface caused by the difference in shrinkage rate, which can prevent deterioration of superconducting properties and make it difficult to use as a coil. It is also possible to prevent a decrease in mechanical strength.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Example 1 0.5mol of Y2O3 powder as raw material for oxide superconductor
%, BaCO3 powder 2m01%, CuO powder 3m01%
Mix these thoroughly and heat at 900°C in the air for 12
After firing for a period of time, the fired product was ground in a ball mill to obtain an oxide superconductor powder. Next, 20 parts by weight of ethyl cellulose was added to 100 parts by weight of this oxide superconductor powder together with an organic solvent as a binder and mixed to obtain a mixture.

In addition, 1mo1% of Y2O3 powder is used as a raw material for electrical insulators.
, 1 mO1% of BaCO3 powder and 1 mO+% of CuO powder were mixed thoroughly and then heated at 600°C in the atmosphere.
After firing for 2 hours, the resulting fired product was treated in the same manner as in the case of the oxide superconductor described above to obtain a mixture.

Next, these mixtures are extruded separately using two extruders, and each of the obtained extrudates is wound up on a drum so that the oxide superconductor and the electrical insulator are alternately located, and the oxidized A spiral molded article was obtained in which a physical superconductor and an electrical insulator were alternately laminated.

Thereafter, the obtained spiral molded product was heat-treated at 500°C to thermally decompose the organic component, and then heated at 930°C in an oxygen-containing atmosphere for 2 hours.
After baking the oxide superconductor and electrical insulator for 4 hours, they are slowly cooled to 600°C or less at a rate of about 1°C/min in an oxygen-containing atmosphere to dissolve the crystal structure of the oxide superconductor. Oxide superconducting coils were obtained by introducing oxygen into the oxygen vacancies.

A perspective view of this coil is shown in FIG. In Figure 1,
The oxide superconducting coil 1 is formed by alternating oxide superconductors and electrical insulators in a spiral shape. Further, a cross section taken along the line AA' in FIG. 1 is shown in FIG. 2. In Figure 2,
Components common to those in FIG. 1 are designated by the same reference numerals as in FIG. 1.

The critical temperature of the oxide superconducting coil obtained in this way is 9
1K, and the critical current density was 240A10+f.

Example 2 To 100 parts by weight of oxide superconductor powder obtained in the same manner as in Example 1, 15 parts by weight of polyvinyl butyral as a binder and 1,1.1-t-lichloroethane and n as a solvent were added.
- Parts by weight of butanol were added and mixed, and after smoothing with a doctor blade, heat treatment was performed to obtain a green sheet with a thickness of 100 μm.

In addition, a green sheet of an electrical insulator made of Y 2 B a Cu O' 5 was obtained in the same manner.

Each of these green sheets is 0.5x 120c
Cut into pieces of m size, 3 pieces for oxide superconductors,
After stacking two electrical insulators, the oxide superconductor and the electrical insulator were alternately stacked in a spiral shape to form a laminate.

Thereafter, the laminate was heated at 930°C in an oxygen-containing atmosphere for 24 hours.
After firing the oxide superconductor and electrical insulator for a period of time, the oxide superconductor and the electrical insulator are slowly cooled at a rate of about 1 °C/min to 600 °C or less in an oxygen-containing atmosphere to form oxygen vacancies in the crystal structure of the oxide superconductor. Oxygen was introduced to obtain an oxide superconducting coil.

The critical temperature of the oxide superconducting coil obtained in this way is 9
0 K, and the critical current density was 140 A/cm.

[Effects of the Invention] As explained above, since the oxide superconducting coil of the present invention can be obtained without converting the oxide superconductor into a wire, it becomes easy to manufacture the oxide superconducting coil using the oxide superconductor. . Furthermore, since a winding process is not required, there is no deterioration in superconducting properties due to mechanical stress during winding, and product variation is also significantly reduced.

Furthermore, when firing oxide superconductors and electrical insulators,
Since the difference in shrinkage is small, it suppresses the occurrence of cracks and distortions that occur on the bonding surface due to differences in shrinkage during manufacturing, and prevents the deterioration of the superconducting properties of the oxide superconductor and the mechanical strength of the coil. It can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the oxide superconducting coil of the present invention obtained in Example 1, FIG. 2 is a sectional view taken along line 8-A' in FIG. FIG. 2 is a schematic diagram showing one method for obtaining a physical superconducting coil by extrusion molding. 1... Oxide superconducting coil 2...
...Oxide superconductor 3...Electric insulator Applicant Toshiba Corporation Patent attorney Sa Suyama −

Claims (4)

[Claims] (1) Oxide superconductor and general formula Ln_2MCuO_5
(Ln is Y, La, Sc, Nd, Sm, Eu, Gd,
An electrical insulator made of ceramics represented by at least one element selected from Dy, Ho, Er, Tm, Yb, and Lu; M is at least one element selected from divalent alkaline earth metals. An oxide superconducting coil characterized in that the coils are formed in close contact with each other and are alternately formed in a spiral shape. (2) The oxide superconducting coil according to claim 1, wherein the oxide superconductor is a perovskite-type oxide superconductor containing a rare earth element. (3) The oxide superconductor contains Ln element (Ln is at least one element selected from rare earth elements), Ba and C
The oxide superconducting coil according to claim 1 or 2, characterized in that the oxide superconducting coil contains u in an atomic ratio of substantially 1:2:3. (4) The oxide superconductor is LnBa_2Cu_3O_7
The oxide superconducting coil according to any one of claims 1 to 3, characterized in that it has an oxygen-deficient perovskite structure represented by _-_δ (δ represents an oxygen defect).