TEMPERATURE-INDEPENDENT, CONSTANT E-J RELATION BELOW TC IN THE CURRENT-INDUCED RESISTIVE STATE OF POLYCRYSTALLINE YBA2CU3O7-X

Restoration of the resistive state of bulk YBa2Cu3O7-x between 4.2 K and T(c) was investigated by transport measurements using J > J(c). Unlike the low-T(c) type-II superconductors, where restoration of the normal-state resistivity is obtained by exceeding J(c) by a fraction of J(c), a constant value of resistivity, which was several to many times smaller than that of the normal-state value, was obtained when J(c) was exceeded in bulk YBa2Cu3O7-x samples. This constant E-J slope remained constant up to ten times the transport J(c). Even more surprisingly, this value was constant for a given sample between 4.2 K and T(c). Near T(c) we observed two breaks in the E-J behavior, which we believe correspond to the inter- and intragrain J(c)'s with the high J(c) in agreement with reported values obtained by magnetization. Microstructural results imply that the mechanism for the observed behavior may be weak-link related.