JPH01143308A - Oxide superconducting coil - Google Patents

Abstract

PURPOSE:To obtain a coil of any given size by stacking a plurality of layers composed of oxide superconductive layers formed like an open helical separated by an air-permeable insulation layer and by connecting them their winding directions of coils in the same direction. CONSTITUTION:In an alumina sintered body, a trough-like body 2 having a notch 1 in the central end of a groove and a trough-like body 4 having a notch 3 in the end of the outer periphery are formed. Oxide superconducting layers 5a and 5b are formed by compressively filling oxide superconductor powder into the grooves of the trough-like bodies 2 and 4. Trough-like bodies 2 and 4 are alternately laminated to obtain a laminate in such a way that the notch 3 of the conducting layer 5b is situated on the outer periphery of a conducting layer 5a, and the notch 1 of another conducting layer 5a is situated on the central end of a conducting layer 5b. The laminate is heat-treated, sintered, and cooled gradually to obtain an oxide superconducting coil. This enables an oxide superconducting coil of a given size to be obtained.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a coil using an oxide superconductor.

(Prior art) In recent years, since it was announced that layered perovskite-type oxides based on Ba-La-Cu-0 may have high critical depletion, research on oxide superconductors has been carried out in various places. (2. Phys, B Condensed Mat
ter64, 189-193 (1986)). Among them, defective perovskite type (LnBa2Cu30□-δ type) with oxygen defects represented by Y-Ba-Cu-0 system.
(δ represents an oxygen defect and is usually 1 or less, [n is Y, L
a, Sc, Nd, Sm, Eu, Gd.

The oxide superconductor of Dy, Ho, Er, Tm, Yb, and [at least one element selected from U, a part of 8a can be replaced with Sr, etc.) has a critical temperature of 90 or higher and a temperature higher than liquid nitrogen. It is attracting attention as a very promising material because it shows a high temperature (Phys, Rev, Lett, V
ol, 58 No. 9.908-910).

By the way, for alloy-based or intermetallic compound-based superconductors, various coils have been investigated for ωI, and NMR
The oxide superconductor is a brittle crystalline oxide, and it is difficult to obtain a wire or tape with good flexibility. It is considered to be extremely difficult to apply this to

Furthermore, even if a coil is molded using an oxide superconductor or its raw material powder and then sintered, it is difficult to introduce oxygen into the oxygen vacancies in the crystal structure of the oxide superconductor to produce superconducting properties. However, after firing, it was necessary to carry out a treatment for introducing oxygen over a long period of time, resulting in extremely low productivity.

(Problems to be solved by the invention) As described above, oxide superconductors have poor flexibility, and even if they are sintered into a coil shape, it is difficult to introduce oxygen into the oxygen vacancies in the crystal structure. It has been extremely difficult to manufacture coils using oxide superconductors.

The present invention was made to solve these problems, and an object of the present invention is to provide an oxide superconductor coil free from the above problems.

[Structure of the Invention] (Means for Solving the Problems) Specifically, in the oxide superconductor coil of the present invention, the plurality of oxide superconductor layers formed in a spiral shape between □ have air permeability. Adjacent ends of adjacent oxide superconductor layers that are laminated with an insulator layer interposed in between are electrically connected so that the winding direction of the coil as a whole is the same. There is.

Many oxide superconductors are known, but
The practical effect is particularly great when a rare-earth element-containing Velor Sky 1-type oxide superconductor with a high critical temperature is used.

The oxide superconductor containing a rare earth element and having a perovskite structure may be one that can practically achieve a superconducting state, such as [nBa2Cu307. , a system (δ represents an oxygen defect and is usually a number of 1 or less, Ln is YXLa, S
c, Nd, Sm, Eu, Gd, Dy, Ho
, Er, Tm.

-5- At least one element selected from vb and [U, 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 perovskite type, such as a 5r-La-Cu-0 system. Rare earth elements are also broadly defined, including Sc, Y and 1. This includes the a series. In addition to the Y-Ba-Cu-0 system, Y is replaced with Eu as a representative system.
, Dy, 110, Er, Tm, Yb, system substituted with rare earth elements such as Lu, 5c-Ba-Cu-0 system, 5r-
Examples include the La-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 follows.

First, the constituent elements of the perovskite oxide superconductor, such as Y, Ba, and Cu, are thoroughly mixed. When mixing,
Oxides such as Y 2 O, [u 2 O, CuO, etc. can be used as raw materials. In addition to these, compounds such as carbonates, nitrates, and hydroxides that are converted into oxides after firing may be used. Furthermore, sikolate etc. obtained by coprecipitation method etc. 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 m
The standard composition is Ba 2 mol and Cu 3 mol for Y 1 mol, but in practice, Ba 2 mol and Cu 3 mol for Y 1 mol
A deviation of approximately 2±0.6 mol and Cu of 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.

The oxide superconductor thus obtained has oxygen defects δ
Oxygen-deficient perovskite structure (LnBa2C
u3o y-6 (δ is usually 1 or less)).

In addition, Ba can also be replaced with at least one of Sr and Ca, and roughly a part of Cu can be replaced with Ti, V, Cr.
, Hn, Fe.

Substitution with Co, Ni, Zn, etc. is also possible.

The amount of 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 set at 80mo 1% or less, or roughly 20mo 1% or less in practice. shall be.

Furthermore, examples of the breathable insulator used in the present invention include porous ceramic sintered bodies, ceramic paper, and the like. Note that the ceramic sintered body is used in the form of a paste composition, a green sheet, or a sintered body block depending on the purpose.

The coil of the present invention is manufactured, for example, in the following manner using the above-mentioned monthly yield.

First, an oxide superconductor layer or its raw material layer is formed in a right-handed and left-handed open spiral shape. As the raw material for forming the oxide superconductor layer or its raw material layer, oxide superconductor raw material powder, oxide superconductor powder, and oxide superconductor can be used. Formation of the oxide superconductor layer or its raw material layer involves compression molding of the forming raw material, punching of a green sheet of the forming raw material, and slicing of a roll-shaped molded sheet of a laminated sheet of a green sheet of the forming raw material and an insulating green sheet. This can be carried out by screen printing, thermal spraying, sputtering, etc. using a forming material made into a paste.

In addition, the insulator layer may be ceramic paper, a green sheet of porous compound insulator, a block of porous ceramic sintered body, or a spiral groove that accommodates the raw material for forming the oxide superconductor layer. A gutter-like body made of porous ceramics or the like can be used.

These oxide superconductor layers or their raw material layers and insulator layers are alternately stacked and sintered together at a temperature of 850 to 980°C. At this time, the center end of the open helix of the oxide superconductor layer or its raw material layer and the center end of one side adjacent to it, and the outer peripheral end of the open helix and the outer peripheral end of the other side adjacent to this, are electrically connected. are superimposed so that they are connected to each other.

In order to make a perfect connection, apply sufficient amount of oxide superconductor powder, its raw material powder, paste-like material thereof, or highly conductive metal powder such as silver or copper to the above electrical connections. It is desirable to place Note that when the insulator layer is thin, the oxide superconductor layer at the connection portion may be simply exposed to bring the layers into direct contact.

After sintering, oxygen is introduced into the oxygen vacancies in the crystal structure in an oxygen-containing atmosphere at 100 to 700°C, or the crystal is slowly cooled at a rate of about 1°C/min at 600°C or less in an oxygen-containing atmosphere. Superconducting properties are improved by introducing oxygen into the oxygen vacancies.

(Function) The oxide superconductor coil of the present invention is constructed entirely of a sintered body, and is formed in an open spiral at a temperature below the critical temperature from one outer layer of the oxide superconductor layer to the other layer. A current flows in a coil toward the

In addition, since the insulating layer has air permeability, oxygen easily flows through the insulating layer when introducing oxygen into the oxygen vacancies in the crystal.
The heat treatment for introducing oxygen can be completed in a relatively short time.

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

Example 1 As shown in FIG. 1(a), an alumina sintered body is used as the insulating layer, and a spiral groove with a width of 3 mm and a depth of 1 mm that expands to the right is formed. has a trough-like body 2 having a notch 1 at the center end thereof, and an open spiral groove 3 mm wide and 1 mm deep that expands to the left, and has a notch 3 at the outer peripheral end of the groove. 10 and 9 gutter-like bodies 4 having the following shapes were respectively molded.

In addition, 0.5mo 1% of Y2O3 powder, 2mo1% of BaCO3 powder, and 3mo1% of CuO powder were thoroughly mixed, this mixture was fired in the atmosphere at 900°C for 12 hours, and the fired product was pulverized with a ball mill and oxidized. It was made into a superconductor powder.

Next, oxide superconductor powder was compressed and filled into the grooves of the trough-like bodies 2 and 4 to form oxide superconductor layers 5a and 5b. A total of 19 gutter-like bodies 2 and 4 on which these oxide superconductor layers 5a and 5b are formed are placed in the oxide superconductor layer 5a.
The notch 3 of the oxide superconductor layer 5b is located on the outer peripheral edge of the oxide superconductor layer 5b, and the notch 1 of another oxide superconductor layer 5a is located on the central end of the oxide superconductor layer 5b. A laminate was obtained by alternately stacking the trough-like bodies 2 and 4 so that the trough-like bodies 2 and 4 were positioned (FIGS. 1(b) and 1(C)).

Thereafter, this laminate was sintered by heat treatment at 980°C for 10 hours in an oxygen-containing atmosphere, and then sintered in an oxygen-containing atmosphere for 6 hours.
An oxide superconductor coil was obtained by slow cooling to 00°C or lower at a rate of 1°C/min.

The critical temperature of this superconductor coil was 94°C.

Example 2 Ceramic paper made of alumina was punched out into a circular shape, and a total of 19 insulator layers were made in two shapes: one with a small hole in the center as a connection part and one with a small hole in the outer edge. Molded.

In addition, oxide superconductor powder was obtained in the same manner as in Example 1,
A binder component and a dispersion medium were added to this oxide superconductor powder to form a paste-like oxide superconductor.

Next, an insulating layer was placed on the binder sheet, and an open spiral pattern was formed by screen printing using a paste-formed oxide superconductor to fill the connection portions. The inter-spiral pattern was unified to either expand to the right or expand to the left depending on the shape of the insulator layer. After the paste-formed oxide superconductor was dried, two insulating layers each having an open spiral pattern were alternately stacked in the same manner as in Example 1 to form a laminate.

The obtained laminate was heat treated in the same manner as in Example 1 to obtain an oxide superconductor coil.

The critical temperature of this superconductor coil was 102°C.

Example 3 A green sheet using alumina powder was punched out in the same manner as in Example 2 to form a total of 18 insulator layers.

Furthermore, a total of 19 open spiral oxide superconductor layers having the same shape as in Example 1 were formed using a green sheet of an oxide superconductor having the same composition as the oxide superconductor used in Example 1.

These oxide superconductor layers and insulator layers were alternately laminated in the same manner as in Example 1 to obtain a laminate.

The obtained laminate was heat treated under pressure in the same manner as in Example 1 to obtain an oxide superconductor coil. At this time, it was confirmed that the green sheets of oxide superconductors were bent by the pressure and came into contact with each other at the connection point between the adjacent oxide superconductor layers via the insulator layer, confirming that they were electrically connected. .

The critical temperature of this superconductor coil was 120°C.

[Effects of the Invention] As explained above, according to the present invention, a coil of any size can be obtained using an oxide superconductor, and it can also be applied to Helmholtz coils and the like.

Further, since a gas-permeable insulating layer between the oxide superconductor layers is used, oxygen can be easily introduced into the oxygen vacancies in the crystal of the oxide superconductor.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a procedure for laminating an oxide superconductor layer and an insulator layer used in the present invention. 2......Trough-like insulator layer having an open helical groove that expands toward the right 4......Having an open helical groove that expands toward the left Trough-like insulator layer 5a...Oxide superconductor layer 5b...Oxide superconductor layer Applicant: Toshiba Corporation Patent Attorney Satoshi Suyama - Figure 1

Claims (7)

[Claims] (1) A plurality of oxide superconductor layers formed in an open spiral are laminated with an air-permeable insulator layer interposed therebetween, and adjacent ends of adjacent oxide superconductor layers are stacked together as a whole. An oxide superconductor coil characterized in that the coils are electrically connected so that the coils are wound in the same direction. (2) The connection between the oxide superconductor layers is between the center end of the open helix of the oxide superconductor layer and the center end of one side adjacent to this, and between the outer peripheral end of the open helix and the other side adjacent to this. The oxide superconductor coil according to claim 1, wherein the outer peripheral end of the oxide superconductor coil is electrically connected to the outer peripheral end of the oxide superconductor coil. (3) The oxide superconductor coil according to claim 1 or 2, wherein the connection between the oxide superconductor layers is made by an oxide superconductor or a normal conductor. (4) The oxide superconductor according to any one of claims 1 to 3, wherein the oxide superconductor is a perovskite-type oxide superconductor containing a rare earth element. coil. (5) The oxide superconductor contains Ln element (Ln is at least one element selected from rare earth elements), Ba and C
The oxide superconductor coil according to any one of claims 1 to 4, characterized in that it contains u in an atomic ratio of substantially 1:2:3. (6) The oxide superconductor is LnBa_2Cu_3O_7
The oxide superconductor coil according to any one of claims 1 to 5, characterized in that it has an oxygen-deficient perovskite structure represented by _-_δ (δ represents an oxygen defect). (7) The oxide superconductor according to any one of claims 1 to 6, wherein the breathable insulator is a porous ceramic sintered body or ceramic paper. coil.