MICROSTRUCTURE AND ELECTROMAGNETIC CHARACTERISTICS OF MULTIFILAMENT V3SI SUPERCONDUCTORS

The V3Si multifilamentary superconductor, which can be fabricated by c ontrolling the diffusion reaction between V and Cu-Si solid-solution a lloy, 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 th e present study, the flux pinning mechanism and the ac loss characteri stics are investigated in correlation with metallurgical microstructur e. 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 pe rpendicular 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 similar to 3 times larger than that of grain boundaries. It was revealed that the V5Si3 layer is effective i n suppressing the proximity coupling between filaments and hence to re duce the hysteresis loss.