OXYGEN DIFFUSION AND CHARGE-TRANSPORT IN THE CUPRATE SUPERCONDUCTORS

Heating of epitaxial c-axis oriented films of YBa2Cu3O7-delta and Nd1. 85Ce0.15CuO4-x in a vacuum results in the generation of large voltages between different points of the film, corresponding to electric field s of 1 V cm(-1) or higher. Apparently, these voltages are due to space charges of opposite sign accumulating near the center and the outer b oundary of the sample, respectively, during the out-diffusion of oxyge n. The sign of the voltage is consistent with the out-diffusion of ion ised 0(--). In order to confirm this behavior, the lateral sample geom etry has been varied systematically. The observed effect promises to y ield important new information on the oxygen diffusion process in the cuprates. Copyright (C) 1996 Elsevier Science Ltd