Thermal Annealing Study of High-T C Ybacuo and Bisrcacuo Superconducting Wires
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THERMAL ANNEALING STUDY OF HIGH-T
c
YBaCuO AND BiSrCaCuO
SUPERCONDUCTING WIRES Y. D. Yaoa,
J. W. Chenb, Y. Y. Chena
P. C. YaoC,
S. J
W. S. Perna, H. A. Yongb, Yangc and S. E. HsuC
I.
N. LinC
a Institute of Physics, Academia Sinica, Taipei, Taiwan, R.O.C. B Department of Physics, National Taiwan University, Taipei, Taiwan, R.O.C. c Materials R & D Center, Chung Shan Institute of Science and Technology, Lungtan, Taoyuan, Taiwan, R.O.C.
ABSTRACT High-T YBaCuO and BiSrCaCuO Superconducting wires have been fabricated by powder metallurgy technique. Copper and silver tubes were used as the external jackets. Thermal annealing treatments for all the wire-type samples were performed between 773 K and 1223 K. Both electrical and magnetization studies show that the superconducting properties can be improved after properly thermal annealing these samples with silver jacket. Our experimental results show that proper thermal annealing treatment can enhance the intragrain critical current density more than 100 times; however, the intergrain critical current density improves only a few times.
INTRODUCTION The discovery of YBaCu oxide superconductor with T exceeding the liquid nitrogen temperature [1] promised wide application in future technology. One of the most intense efforts in research and development for these high T superconductors recently is directed towards the thin film [2] for electronic use and the wire [3-8] for energy use. The cold powder metallurgy technique was used to fabricate the conventional A15 superconducting thin wires [9]. However, it has not been sure if the high T oxide superconductors can be fabricated into a long wire type to be used for superconducting magnets. Therefore, we are very interested to fabricate YBaCuO and BiSrCaCuO superconductors thin wires and to study their physical properties. In this paper, we presented the experimental results of thermal annealing study of high-T YBaCuO and BiSrCaCuO thin wires by powder metallurgy technique, and their significance are discussed.
EXPERIMENTAL PROCEDURE Samples for this study were prepared by using high purity Y2 0, Bi 2 Co , BaCo 3 , SrCo 3 , CaCo 3 , and CuO powders. The proper mixed powders, i-paced in alumina crucibles, were heated in flowing oxygen for 16 hours at 1223 K for YBaCuO superconductors and 1133 K for BiSrCaCuO superconductors. The process was repeated after pulverizing of the treated mixture. The resultant oxide compound was packed into both Cu and Ag tubes with outer diameter of 12.7 mm for Cu tubes and 10.0 mm for Ag tubes. This composite was swaged and wire drawn to final size. Swaging techniques were used for Mat. Res. Soc. Symp. Proc. Vol. 169. G1990 Materials Research Society
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Fig. 1. Micrograph of polished cross section of a BiSrCaCuO thin wire (diameter: 1.0 mm) with copper tube as the external jacket.
the preliminary stages, and the remaining deformation to a wire with a final diameter of roughly 1.0 mmwas made by wire drawing. Nominal areal reduction ratio of about 160 were obtained without any intermed
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