Processing yttrium-barium-copper oxide superconductor zero gravity using a double float zone surface

The effects of processing YBa2Cu3Ox (Y123) superconductor in the near-zero gravity (0g) 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-gram sample was processed with each parabola. Samples of Y123 were processed as bulk sheets, composites containing Ag and Pd, and films deposited on single crystal Si and MgO substrates. The 0g-processed samples were multi-phase yet retained a localized Y123 stoichiometry where a single ground-based (1g) oxygen anneal at temperatures of 800 C recovered nearly 100-volume percent superconducting Y123. The 1g processed control samples remained multi-phase after the same ground-based anneal with less than 45 volume percent as superconducting Y123. The superconducting transition temperature was 91 K for both 0g and 1g processed samples. A 29 wt.% Ag/Y123 composite had a transition temperature of 93 K. Melt texturing of bulk Y123 in 0g produced aligned grains about a factor of three larger than in analogous 1g samples. Transport critical current densities were at or below 18 A/cm2, due to the formation of cracks caused by the rapid heating rates required by the short time at 0g. Y123 deposited on single crystal Si and MgO in 0g was 30 vol.% y123 without an anneal. A weak superconducting transition at 80 K on MgO showed that substrate interactions occurred