Electric field versus current density curves in melt-textured samples of YBa2Cu3O7-delta under currents well above the critical current

摘要

In this work, we present measurements of the E-J curves of top seeded melt-textured YBa2Cu3O7-delta. The samples, with a typical 0.5 mm(2) cross section, were cut from monoliths grown up to 2 cm in diameter (ab-planes direction) and 0.7 cm in height (c-axis direction). The E-J characteristics were measured up to current densities several times larger than the critical current density J(C). To avoid spurious heating, current pulses up to 200 A and 1-3 ms long were applied through the samples immersed in liquid nitrogen. Measurements were carried out in the temperature range 80-93 K by pressuring the nitrogen bath. An abrupt electric-field jump is observed, in the E-J curves, for a current density J* several times higher than J(C). This jump at J* is to some extent similar to the one observed in thin films. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 3]