PULSED CRITICAL CURRENT MEASUREMENTS ON YBCO WIRES AND SCREEN-PRINTED FILMS

Measurements of critical current densities in YBCO wires and thick films have been made using a pulsed current facility to avoid problems from ohmic heating at the electrical contacts. The measurements on bulk ceramic and extruded wire samples are considered in terms of thermally activated voltage arising from the unpinning of flux lines and a steady state flux flow regime. For textured thick film samples produced by screen-printing, critical current densities in excess of 500 A cm-2 at liquid nitrogen temperature have been achieved. The properties of such films are highly dependent on processing temperature and, in contrast to bulk and wire samples, the critical currents in such films are highly anisotropic with respect to field direction relative to the current. Also, their resistance in the flux flow regime relative to their normal state resistance is almost two orders of magnitude smaller than observed for bulk samples. © 1990.