日本金属学会誌

J. Japan Inst. Metals, Vol. 62, No. 8 (1998),
pp. 727-734

Microstructure and Electromagnetic Characteristics of MultifilamentV3Si Superconductors

Takao Takeuchi, Yoshihiro Nemoto, Hiroshi Maeda, Kikuo Itoh,Kiyoshi Inoue}$ Research Group, Leader}, Michio Kosuge, Michinari Yuyama and Hitoshi Wada

Tsukuba Magnet Laboratory, National Research Institute for Metals, Tsukuba 305-0003

Abstract:

The V3Si multifilamentary superconductor, which can be fabricated by controlling the diffusion reaction between V and Cu-Si solid-solution alloy, is promising as a new A15-type multifilamentary conductor for ac use, since it is possible to leave appropriately a normal-conducting V5Si3 layer as a high-resistivity barrier around V3Si filaments. In the present study, the flux pinning mechanism and the ac loss characteristics are investigated in correlation with metallurgical microstructure. Angular dependence of flux pinning force with respect to the field direction, for a flattened conductor, was well fitted to the proposed model in which two kinds of ellipsoidal-microstructure are mutually perpendicular and act as pining centers, respectively. We could thereby confirm that both the grain boundary and the superconducting(S)/normal conducting(N) interface act as the pinning centers. Elemental pinning force of the SN interface is 2{~}3 times larger than that of grain boundaries. It was revealed that the V5Si3 layer is effective in suppressing the proximity coupling between filaments and hence to reduce the hysteresis loss.


(Received March 9, 1998; In Final Form May 27, 1998)

Keywords:

flux pinning center, superconducting/normal conducting interface, grain boundary, hysteresis loss, high resistivity barrier, V5Si3 layer, proximity coupling


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