Abschirmverhalten von Niob-Zinn-Sintermaterial bei zugabe von fremdelementen

Abstract

After an initial survey on the shielding behaviour of high field superconductors, experiments are reported on the effect of systematic variations in the preparation of NbSn sinter material on the shielding capabilities. Shielding fields up to 45 kA cm −1 for a wall thickness of 1 mm could be obtained by adding Cu, Ag or Au to the unsintered powder mixture and reducing the sintering temperature. To explain this effect we have assumed the existence of an equilibrium between the A15 phase and the liquid in the ternary system at lower temperatures than in the binary NbSn system (limit 920 °C) so that the barrier preventing the relatively rapid formation of the A15 phase in the ternary system is removed. Due to the lowering of the sintering temperature made possible by this process, the critical current density in the A15-phase of the sinter specimen and, correspondingly, the shielding capabilities are increased.