Production of MgO dispersed Bi-2223 superconductor

Details Production of MgO dispersed Bi-2223 superconductor Production of MgO dispersed Bi-2223 superconductor

1996-05-03

2001-04-03

Hughes, S. Thomas (Department: 3726)

Metal working

Method of mechanical manufacture

Electrical device making

C505S433000, C505S425000

Reexamination Certificate

active

06209190

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high T
c
superconductor and more particularly to fine MgO dispersed Bi-2223 high T
c
superconductor.
2. Description of the Prior Art
Since the discovery of high-T
c
oxide superconductor, many studies have been made to obtain wire with high critical current density. Microstructural control is important to keep the high critical current density under magnetic field for practical application of superconducting materials. Major problems in BSCCO superconductors are impurities in grain boundary and degradation of Jc under magnetic field due to flux creep. It is relatively easier to process BSCCO superconducting systems to high Jc as compared to YBCO due to their low melting temperature and aligning texturing by a proper mechanical or thermal processing. However, this system exhibits a serious flux creep behavior under magnetic field, requiring very effective flux pinning centers. In YBCO system, it was reported that finely dispersed non-superconducting 211 particles provided flux pinning mechanism. It seems that non-superconducting fine particle which does not react with superconducting matrix can provide flux pinning mechanism.
It is well known that significant magnetic field penetration can occur in the interior of BSCCO superconductors above a critical magnetic field (Hc 1). If the magnetic flux lines within the superconductor are not strongly pinned in place, then Lorentz forces can cause the flux lines to migrate, resulting in resistive energy dissipation. The BSCCO superconductors have been found to exhibit significant flux creep in modest magnetic fields at temperatures well below the critical temperature.
Therefore, the application of these materials in high magnetic fields is seriously limited unless the flux creep is reduced by enhanced flux pinning. The operating temperature and magnetic field will have to be reduced to less than 30K, and few tesla for the BSCCO system. Based on the observation of Yamaguchi et al. who increased the pinning of YBCO ceramics by the introduction of the second phase [see J. Mater.Res. 6, 1404 (1991)], several researchers claimed that Ca
2
CuO
3
increases the pinning of the 2212 and 2223 phase of the BSCCO superconductors. However, the grains of powdered metallurgically processed ceramics are too large (1-100 &mgr;m) to act as effective pinning centers.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to overcome the flux creep behavior under magnetic field.
In order to accomplish the above object, the present invention uses fine MgO particle. MgO is known not to react with Bi-2223 superconductor and very fine MgO particles such as 100 Å in size are available commercially. The present invention provides a method by which addition of very fine MgO particle in Bi-2223 superconductor can improve the critical current density under magnetic field.
In accordance with the present invention mixture of Bi, Pb, Sr, Ca, Cu salts is pre-reacted to give intermediate phases such as Bi-2223, Bi-2212 and Ca
2
PbO
4
because it is known that the complete conversion to Bi-2223 is very sluggish.
The pre-reacted powder is mixed with the appropriate amount of fine MgO particles and heat-treated to give B-2223 superconductor in which fine MgO particles are embedded. The resulting microstructure is such that fine MgO particles are trapped inside the Bi-2223 grains. When MgO particles are located at grain boundaries of Bi-2223 grains they provide weak links which decrease the critical current density.


REFERENCES:
patent: 5028585 (1991-07-01), Spencer
patent: 5061683 (1991-10-01), Horowitz
patent: 5079215 (1992-01-01), Kugimiya et al.
patent: 5118659 (1992-06-01), Lafon et al.
patent: 5152973 (1992-10-01), Spencer
patent: 5238911 (1993-08-01), Kuwajima et al.
patent: 5284822 (1994-02-01), Sakai et al.
patent: 5409890 (1995-04-01), Yamamoto et al.
patent: 0564238 A1 (1993-10-01), None
patent: 5-310428 (1993-11-01), None
Yoo et al., “Effect of MgO Particles on Microstrucutral Development and Superconducting Properties of Bi-2223 Phase”; IEEE Transactions on Applied Superconductivity, vol. 5, No. 2, Jun. 1995, pp. 1479-1481.
Ko et al., “Fabrication and Properties of Ultra Fine MgO Added Bi-2223/MgO/Ag Tapes”; Advances in Super Conductivity, Proceedings of the 8th International Symposium on Superconductivity (ISS '95), Oct. 30-Nov. 2, 1995;ISTEC, vol. 2; pp. 839-842.

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