JPH04321552A - Superconducting member - Google Patents

Abstract

PURPOSE:To improve the superconducting characteristics such as critical current density of a superconducting material produced by using a bulk oxide superconductor. CONSTITUTION:Oxide superconductor layers 1 and oxygen-transmission layers 2 made of a material having excellent oxygen permeability such as silver are alternately laminated and the laminate is baked in an oxygen-containing atmosphere to effect the sintering of the layers while uniformly supplying oxygen to the core part of the oxide superconductor layers 1 and to integrate the layers as a superconducting material.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to superconducting members using high temperature superconducting materials such as oxide superconductors.

0003

[Prior Art] In 1986, Bednorz and Mul
Since Ler et al. first reported that La-Ba-Cu-O-based oxides have superconductivity, several oxide-based superconductors having a perovskite structure have been discovered. Many of them have high critical temperature (Tc)
, especially Y-Ba-Cu-O system (Tc=93K
), Bi-Sr-Ca-Cu-O system (Tc=80K
, 108K), Tl-Ba-Ca-Cu-O system (T
c=125K) etc., the Tc is the liquid nitrogen temperature (7
It is attracting attention as it exceeds 7.3K).

[0004] One of the main fields of application of such oxide superconductors is considered to be the field of electric power and energy equipment. The forms of oxide superconductors used in this field can be roughly divided into long wire rods with a sheath material and short bulk wire rods without a sheath material, and each can have various uses. ing. To give a specific example,
Wire materials include wire materials for power transmission cables and superconducting magnets.
Examples of bulk materials include current leads and current limiting elements.

[0005] The above-mentioned current lead connects a power source to superconducting applied equipment such as a superconducting magnet or a superconducting current limiter to supply current, and has the advantage of being able to stably flow a large current and being difficult to conduct heat. This is a necessary condition. Oxide superconductors have low thermal conductivity and can conduct current up to high temperatures without Joule heat generation, making them suitable for current leads. In addition, current flowing through polycrystalline oxide superconductors at present rapidly attenuates in response to magnetic fields, which also makes them useful as current leads and current-limiting elements that are less affected by magnetic fields. is being developed.

[0006]

[Problems to be Solved by the Invention] As mentioned above, one of the application fields of oxide superconductors is the use of bulk materials of oxide superconductors for current leads, etc. The method of manufacturing bulk materials using the solid phase method has the disadvantage that it is difficult to stably obtain materials having a sufficiently large critical current density. Therefore, in order to supply sufficient current to a superconducting magnet or the like, it is necessary to increase the cross-sectional area of the current lead. In this way, increasing the cross-sectional area not only increases the size of the current lead device, but also increases the amount of heat intrusion from the outside, although oxide superconductors have low thermal conductivity.
This results in problems such as reduced functionality of superconducting equipment and increased running costs. For these reasons, it is strongly desired to improve the critical current density of oxide superconducting bulk bodies used as current leads and the like.

Furthermore, the above-mentioned current lead is one application example of a superconducting member using a bulk material of an oxide superconductor, and if it is possible to improve the critical current density of the bulk material of an oxide superconductor, Application to various uses becomes possible.

[0008] The present invention has been made to address these problems, and an object of the present invention is to provide a superconducting member with improved superconducting properties such as critical current density of a bulk material of an oxide superconductor. .

[Configuration of the invention]

0010

[Means for Solving the Problems] That is, the superconducting member of the present invention is a superconducting member using an oxide superconductor, and is constructed by integrally laminating the oxide superconductor and oxygen permeable layers alternately. It is characterized by the fact that

The oxide superconductor used in the present invention is not particularly limited as long as it can realize a superconducting state; for example, an oxide superconductor having a perovskite structure containing rare earth elements, Bi-Sr, etc.
-Ca-Cu-O based oxide superconductor, Tl-Ba-Ca
-Cu-O based oxide superconductor etc. are applied.

Examples of the above-mentioned oxide superconductor containing rare earth elements and having a perovskite structure include RE
M2 Cu3 O 7-δ system (RE is Y, La, Sc
, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm,
At least 1 selected from rare earth elements such as Yb and Lu
M is at least one element selected from Ba, Sr, Ca, δ is an oxygen defect and is usually a number of 1 or less, a part of Cu is Ti, V, Cr, Mn, Fe,
Examples include oxides of Co, Ni, Zn, etc.) which can be substituted with Co, Ni, Zn, etc.

[0013] Furthermore, the Bi-based oxide superconductor has the chemical formula:
Bi2 (Sr,Ca)3 Cu2 Ox Bi2
Sr2 Ca2 Cu3 Ox Bi2 Sr2 C
a3 Cu4 Ox (in the formula, part of Bi can be replaced with Pb, etc., and part of Sr and Ca can be replaced with rare earth elements, etc.), and Tl-Ba-Ca-Cu
The -O-based oxide superconductor also has a similar structure.

Further, as the constituent material of the oxygen permeable layer in the present invention, it is possible to use, for example, metal materials such as silver, gold, platinum, and nickel. For example, silver itself is difficult to oxidize, as can be seen from the fact that it is also used as a sheath material for oxide superconductors, and it allows oxygen to permeate through it, functioning as an oxygen supply source for oxide superconductors. . Further, the oxide superconductor is not reduced to lose its superconductivity, and the oxide superconductor is not combined with the oxide superconductor to form a new compound. Furthermore, it has low electrical resistance and is rich in ductility and malleability, so that sufficient contact with the oxide superconductor can be obtained.

A specific form of the superconducting member of the present invention is, for example, as shown in FIG. 1, in which oxide superconductor layers 1 and oxygen permeable layers 2 are alternately laminated and these are integrated. Can be mentioned. Further, the overall shape may be selected depending on the member to which it is applied; for example, if it is used as a current lead, the lead shape may be casing-like. Also, if used as a current limiting element,
It may have a similar shape or may have a meander shape or the like. In addition, the oxygen permeable layer may be in the form of a sheet, but it is also possible to use a shape such as a net or a punched sheet that allows adjacent oxide superconductors to come into direct contact with each other. preferable. This makes it possible to further ensure the soundness of the superconducting member (sintered body).

The superconducting member of the present invention is manufactured, for example, by the method shown below.

That is, first, individual oxide superconductor layers are formed. This oxide superconductor layer may be formed by forming oxide superconductor powder into a sheet by a doctor blade method or the like, or may be a green compact of oxide superconductor powder. Next, these oxide superconductor layers and oxygen permeable layers having similar external shapes are alternately laminated, and then fired in an oxygen-containing atmosphere to integrate and sinter them. Further, after sintering, heat treatment in oxygen or the like is performed as necessary.

[0018]

[Operation] In the superconducting member of the present invention, since an oxygen permeable layer made of silver or the like is interposed between the oxide superconductors,
When sintering the oxide superconductor, oxygen is uniformly supplied to the inside of the oxide superconductor by the oxygen permeable layer. Therefore, the entire oxide superconductor comes to exhibit healthy superconducting characteristics, and it becomes possible to improve, for example, the critical current density of the superconducting member.

[0019]

[Embodiments] Hereinafter, embodiments of the superconducting member of the present invention will be described.

Example First, raw material powder for an oxide superconductor was prepared as follows. Y2 O3 powder, BaCO3 powder and C
uO powder in atomic ratio Y:Ba:Cu=1:2:3
After weighing out a predetermined amount and thoroughly mixing it, it was heat-treated in the atmosphere at 860° C. for 24 hours, and ground in a mill to obtain calcined powder. Next, an appropriate amount of an organic binder and a dispersion medium were added to the above calcined powder, and after thorough mixing, a 130 mm x 13 piece was prepared using a doctor blade method.
A sheet-like product measuring mm×0.9 mmt was molded.

Next, the above-mentioned sheet-like material and a silver net having a thickness of 0.5 mm and having the same external shape were laminated alternately so that the outermost layer was an oxide superconductor layer, and the sheets were pressed together. They were roughly integrated by pressing to produce a 15-layer laminate. Thereafter, the above laminate was fired in oxygen at 900°C for 24 hours, and further held at 500°C for 12 hours during cooling to obtain the desired superconducting member.

On the other hand, as a comparison with the present invention, a molded product having a similar shape was produced by press molding using the above-mentioned calcined powder, and then fired in oxygen at 900°C for 24 hours. A similar holding treatment was performed during the firing to obtain a sintered body of an oxide superconductor having the same shape as the above-mentioned superconducting member after firing.

[0023] When the critical current density of the superconducting members of Examples and Comparative Examples thus obtained was measured under the conditions of 77K and 0T, it was found that the superconducting members of Examples had a critical current density of 2000A/
cm2, which was a good value, whereas the superconducting member according to the comparative example only obtained a low value of 500 A/cm2.

[0024]

As explained above, according to the superconducting member of the present invention, a uniform superconducting state can be obtained throughout the interior due to the oxygen supplying ability of the oxygen permeable layer, so that the superconducting properties of the superconducting member as a whole can be improved. It becomes possible to achieve this goal. Therefore, it becomes possible to use the bulk material of the oxide superconductor for various superconducting members including current leads, current limiting elements, and the like.

[Brief explanation of the drawing]

FIG. 1 is a partially cross-sectional perspective view showing the configuration of an example of a superconducting member according to the present invention.

[Explanation of symbols]

1...Oxide superconductor 2...Oxygen permeable layer

Claims (1)

[Claims] 1. A superconducting member using an oxide superconductor, characterized in that the oxide superconductor and oxygen permeable layers are alternately laminated and integrated.