Critical current density of Ba2Y1Cu3O7−x superconducting filaments produced by various suspension spinning conditions

Abstract

The suspension spinning of a Ba2Y1Cu3Ox superconductor under various conditions was studied to prepare a long filament with high Jc. The oxide powder was suspended in a PVA solution containing a dispersant. The viscous suspension was extruded as a filament into a precipitating medium and coiled on a winding drum. The obtained filament was heated to remove volatile components and to generate the layered perovskite phase. The spinning was examined in an aqueous system and a nonaqueous system. The filament with higher Jc was obtained for the nonaqueous solution. The Jc was dependent on the fineness of the starting oxide powder, solvent, precipitating medium, degree of polymerization of PVA, the kind of dispersant used, and the oxide powder contents of the spinning dope, as well as the heating condition. The highest Jc value obtained by resistivity measurement at 77 K and zero field, 680 A/cm2, was attained for the filament spun under optimum spinning conditions. The magnetization curve of the filament showed that the material was a type II superconductor. The hysteresis of thin filaments was relatively small compared with that for the thick filaments. The Jc at 79 K, estimated from the magnetization curve, was one order of magnitude higher than the Jc measured by the resistivity method and decreased drastically with increasing field.