Processing yttrium barium copper oxide superconductor in near-zero gravity

Abstract

The effects of processing YBa 2Cu 3O x (Y123) superconductor in the near-zero gravity (0 g) environment provided by the NASA KC-135 airplane flying on parabolic trajectories were studied. A new sheet float zone furnace, designed for this study, enabled fast temperature ramps. Up to an 18 g sample was processed with each parabola. Samples of Y123 were processed as bulk sheets and composites containing Ag and Pd. The 0 g processed samples were multi-phase yet retained a localized Y123 stoichiometry where a single ground-based (1 g) oxygen anneal at temperatures of 800°C recovered nearly 100 vol% superconducting Y123. The 1 g processed control samples remained multi-phase after the same ground-based anneal with less than 45 vol% as superconducting Y123. The superconducting transition temperature was 91 K for both 0 g and 1 g processed samples. Melt texturing of bulk Y123 in 0 g produced aligned grains about a factor of three larger than in analogous 1 g samples. Transport-critical current densities were at or below 18 A/cm 2, due to the formation of cracks caused by the rapid heating rates required by the short time at 0 g.