Structure and properties of rapidly quenched microcrystalline alloys with immiscible elements: The case of superconducting PbBiGe

Abstract

The preparation of PbBiGe ribbons including finely dispersed immiscible particles of germanium was investigated under two different experimental conditions: rapid quenching under helium gas with a substrate velocity of 50 m s − and slow quenching under vacuum with a substrate velocity of 3 m s −1. These latter conditions have been chosen in order to approach those of the glass-coated melt-spinning process used previously by Goto giving high T c superconducting materials. The melt-spinning process has been found to result in the preparation of superconducting material having a mixed structure of cubic germanium particles finely dispersed in a PbBi matrix consisting of the two ε(h.c.p.) and bismuth (h.c.p.) phases. Susceptibility measurements reveal that the bulk nature of superconductivity remains unchanged, and resistive measurements show no significant drop in T c. Possible mechanism for superconductivity able in some cases to give rises in T c will be discussed with respect to those given earlier.