JPH0719688B2 - Superconductor junction structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a superconductor junction structure for forming superconductivity of an oxide superconductor on a substrate.

"Prior Art" Conventionally, as a joining structure of a superconductor such as a superconducting magnet coil, for example, a structure in which a thin wire made of an alloy superconducting material such as an Nb-Ti alloy is wound around a base made of a normal conductor, or Nb A structure is known in which a compound-based superconducting material such as ₃ Sn is soldered on a substrate, and then the compound-based superconducting material is mechanically cut into a coil shape.

By the way, recently, the La-Ba-Cu-O system whose critical temperature is 50 ° K or higher,
In general, the chemical formula of Y-Ba-Cu-O system is AxByCuzO ₃ (A: Sc, Y, La
Perovskite-type oxide-based superconductors represented by Group IIIA metal elements of the periodic table of ..., Alkaline earth metals of B: Ba, Sr, Be ... are being found one after another. Since these oxide-based superconductors have excellent characteristics such as a higher critical temperature than the above-mentioned alloy-based or compound-based superconductors and being considered as a superconducting material above the liquid nitrogen temperature, they are suitable for superconducting magnet coils and the like. Is expected to be applied and put to practical use.

"Problems to be Solved by the Invention" However, in the above oxide-based superconductor, since the oxide-based superconductor is an oxide, the bonding with a normal conductor made of a metal such as copper is poor. There's a problem.

[Means for Solving the Problems] Therefore, in the junction structure of the superconductor of the present invention, the constituent elements of the base and the oxidation are provided between the base made of the normal conductor and the superconducting layer made of the oxide superconductor. The above problems were solved by forming a grading layer composed of constituent elements of a physical superconductor and increasing the constituent element concentrations of the substrate in the grading layer on the substrate side and on the superconducting layer side.

"Embodiment" FIG. 1 is a diagram showing an embodiment in which the superconductor junction structure of the present invention is applied to a superconductor magnet coil, and reference numeral 1 in the drawing is a superconducting magnet coil. The superconducting magnet coil 1 includes a circular base tube 2, a spiral superconducting circuit 3 formed on the base tube 2, and a grading layer 4 formed between the base tube 2 and the superconducting circuit 3. It consists of

The base tube 2 is made of a normal conductor, and copper is preferably used as the normal conductor. The superconducting circuit 3 is composed of an oxide superconductor formed on the outer peripheral surface of the base tube 2 via a grading layer 4 described later. Here, as the oxide-based superconductor, a perovskite type represented by the chemical formula AxByCuzO ₃ is used. This perovskite type is composed of an oxide powder of a Group IIIA metal element (A in the above chemical formula) of the periodic table, a carbonate powder of an alkaline earth metal (B in the above chemical formula) and a copper oxide powder in an appropriate ratio. It is formed by being mixed and fired, and the mixing ratio of these powders varies depending on the oxide-based superconductor desired.
For example, in the above chemical formula (x + y = 1, z = 1),
The composition is such that (x + y = 2, z = 1) and (x + y = 2, z = 1.25) are satisfied.

The grading layer 4 includes the outer peripheral surface of the base tube 2 and the superconducting circuit 3.
It is formed in a spiral shape between and, and is formed by laminating a plurality of thin single layers 4a, 4b ... As shown in FIG. The single layers 4a, 4b ... Are the elements (that is, scandium (S) that constitute the oxide-based superconductor to be the superconducting circuit 3 described above.
c), yttrium (Y), lanthanum (La), and other lanthanides, Group IIIA metal elements and barium (Ba), strontium (Sr), calcium (Ca), beryllium (Be), and other alkaline earths It has a composition in which an element that constitutes the base tube 2, that is, a copper element is added to a group of metals, copper, and oxygen), that is, a copper element is added in the present embodiment, and the concentration of the copper element is different from each other. Single layer 4a in contact with the base pipe 2
Is a large proportion of the copper element, and the weight ratio of the element forming the above oxide-based superconductor to the copper element is about 1: 4. The weight ratio of the single layer 4b formed on the single layer 4a is about 2: 3, the single layer 4c formed on the single layer 4c is about 3: 2, and the superconductivity formed on the single layer 4c. Single layer in contact with circuit 3
4d has a large proportion of the material composed of the elements constituting the oxide-based superconductor, and the weight ratio thereof is about 4: 1. Due to such arrangement of the single layers 4a, 4b, ..., The grading layer 4 has a concentration gradient in which the concentration of the copper element is high on the base tube 2 side and low on the superconducting circuit 3 side.

In order to create the superconducting magnet coil 1 having such a structure, first, as shown in FIG.
A cylindrical single-layer body 5a corresponding to the single-layer 4a is formed by means of sputtering, vacuum deposition, etc., and further the single-layer body 5b,
5c and 5d are sequentially formed. Here, in the case of forming the monolayer body 5a, for example, by firing, powder of the material constituting the monolayer 4a, that is, oxide powder of Group IIIA metal element of the periodic table and carbonate of alkaline earth metal. Chemical formula AxBy when salt powder, copper oxide powder, copper metal powder, etc. are fired and molded
The weight ratio of the oxide superconductor represented by CuzO ₃ to copper is 1: 4.
Are mixed so that water, a binder and the like are appropriately added to form a paste, and the paste is fixed on the base tube 2 and heated and baked. In this case, the monolayer body 5a is the base tube 2
As described above, the proportion of the copper element constituting the is high, and since it has a property close to that of the base pipe 2, it is firmly joined to the base pipe 2. Further, when forming the single-layer bodies 5b, 5c, and 5d, similarly, those which are blended according to the single layer corresponding to each single-layer body and which are adjusted into a paste form are sequentially laminated and fired. Also in this case, since each of the monolayer bodies 5b, 5c, and 5d has a composition close to that of the monolayer body as the lower layer, the monolayer bodies are firmly bonded to these lower monolayer bodies. In the case of firing, firing may be performed for each single layer body, or paste materials corresponding to the respective single layer bodies may be sequentially laminated in advance and fired at once.

Next, on the single-layer body 5d formed on the outermost peripheral side, a paste-like material of the oxide-based superconductor material corresponding to the superconducting circuit 3 is fixed and fired to form a cylindrical superconductor 6
And Also in this case, the superconductor 6 is a monolayer body below it.
Since it has a composition close to that of 5d, it is firmly bonded to the monolayer body 5d. When firing, the superconductor 6 may be formed at the same time as the single-layer body by firing at the same time as the paste-like material that becomes the single-layer body.

After this, this superconducting material 6 and the above monolayers 5a, 5b, 5c, 5d
A known mechanical means such as cutting or a known chemical means such as etching to remove a part of
As shown in FIG. 1, a spiral superconducting circuit 3 is formed and a single layer 4a, 4b, 4c, 4d is formed between the superconducting circuit 3 and the base tube 2.
The grading layer 4 made of is formed to obtain the superconducting magnet coil 1.

In the superconducting magnet coil 1 having such a structure, the grading layer 4 is provided between the base tube 2 and the superconducting circuit 3.
Since the grading layer 4 has a composition close to that of the base tube 2 on the side of the base tube 2 and that of the superconducting circuit on the side of the superconducting circuit 3, the grading layer 4 has characteristics such as expansion coefficient. 2 and the superconducting circuit 3 do not change abruptly and the grading layer 4 changes the difference in these characteristics stepwise, thus preventing inconvenience such as heat shock due to the difference in characteristics such as the expansion coefficient. To be done. Further, since the superconducting circuit 3 and the base tube 2 are not directly joined to each other through the grading layer 4 having a composition close to each other, the superconducting circuit 3 and the base tube 2 having different properties can be joined easily. .

Although the grading layer 4 is formed of a plurality of single layers in the above embodiment, it may be formed of a single layer having a copper element concentration gradient. In that case, the single layer is formed. To do so, for example, a tube body made of an oxide-based superconductor is formed, then cylindrical copper is inserted into the inner hole of the tube body, and then the tube body and copper are heated and melted by an appropriate means. Copper is diffused into the tubular body, after which the cylindrical copper is removed to obtain a tubular monolayer having a copper concentration gradient.

Further, in the above-mentioned embodiment, a circular tube-shaped superconducting magnet coil is shown, but in addition, as shown in FIG. 4, for example, a spiral superconducting circuit 8 is formed on a disk-shaped substrate 7, and A superconducting magnet coil in which a grading layer 9 is formed between the superconducting circuit 8 and the superconducting circuit 8 may be used.

Further, the present invention may be applied to the superconducting wire 10 as shown in FIG. The superconducting wire 10 is formed by forming a superconducting layer 13 made of an oxide superconductor on a base wire 11 made of a normal conductor such as copper, aluminum or tin sulfide with a grading layer 12 interposed therebetween. Here, the grading layer 12 is
It has a composition in which the elements that form the baseline 11 are added to the elements that form the superconducting layer 13, and the concentration of the elements that form the baseline 11 is high on the baseline 11 side and low on the superconducting layer 13 side. It is a thing.

"Effects of the Invention" As described above, the joining structure of the superconductor of the present invention has a structure in which the constituent element of the base and the oxidation are provided between the base made of the normal conductor and the superconducting layer made of the oxide superconductor. Since a grading layer made of constituent elements of the physical superconductor is formed and the constituent element concentration of the substrate in the grading layer is high on the substrate side and low on the superconducting layer side, characteristics such as expansion coefficient are The characteristics of these characteristics are gradually changed by the grading layer without abruptly changing between the substrate and the superconducting layer, and therefore heat shock and the like due to the difference in characteristics such as the expansion coefficient can be prevented. Therefore, it is possible to prevent inconvenience such as thermal distortion due to temperature change. Moreover, since the superconducting layer and the base are not directly joined to each other through the grading layers having similar compositions, the superconducting layer and the base having different properties can be easily joined.

[Brief description of drawings]

1 to 3 are views showing an embodiment in which the superconductor junction structure of the present invention is applied to a superconducting magnet coil. FIG. 1 is a partial sectional view showing the superconducting magnet coil. FIG. 4 is an enlarged cross-sectional view of a main part, FIG. 3 is an enlarged cross-sectional view of a main part for explaining a method of manufacturing the superconducting magnet coil, and FIG. 4 is another embodiment in which the present invention is applied to the superconducting magnet coil. FIG. 5 is a schematic diagram of a superconducting magnet coil, and FIG. 5 is a diagram showing an embodiment in which the present invention is applied to a superconducting wire,
It is a schematic block diagram of a superconducting wire. 1 ... Superconducting magnet coil, 2 ... Base tube, 3, 8 ...
… Superconducting circuit, 4, 9, 12 …… Grading layer, 7…
… Substrate, 10 …… Superconducting wire, 11 …… Base line, 13 …… Superconducting layer.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shotaro Yoshida 1-5-1, Kiba, Koto-ku, Tokyo Within Fujikura Electric Wire Co., Ltd. (72) Inventor Shoichi Hasegawa 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Line Co., Ltd. (72) Inventor Hiroshi Yamanouchi 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Line Co., Ltd. (72) Inventor Shigeyoshi Yokoyama 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd.

Claims (1)

[Claims] 1. A junction structure of a superconductor in which a superconducting layer made of an oxide superconductor is formed on a base made of a normal conductor, wherein a constituent element of the base is provided between the base and the superconducting layer. A superconductor junction structure characterized in that a grading layer made of the constituent elements of the oxide-based superconductor is formed, and the constituent element concentrations of the base in the grading layer are high on the base side and low on the superconducting layer side. .