A15 Nb3(AlGe) superconductors prepared by transformation from liquid quenched body-centered cubic phase

Abstract

A supersaturated body-centered cubic (bcc) solid solution of Nb 3(Al1-xGex) up to x = 0.3 has been prepared by the liquid quenching on a hot Cu substrate. The quenched materials are then transformed to the A15 structure by annealing above 800°C. Following the transformation, the critical temperature rises above 18°K. The A15 phase converted from the bcc phase has an extremely small grain size of a few hundred angstroms, resulting in a high critical current density Jc in high magnetic fields. Jc of 3.5×105 A/cm2 at 4.2°K and 16 T has been achieved in the Nb3(Al 0.8Ge0.2) sample annealed at 850°C for 7 h.