Oxygen diffusion and charge transport in the cuprate superconductors

Heating of epitaxial c-axis oriented films of YBa2Cu3O7-δ and Nd1.85Ce0.15CuO4-x in a vacuum results in the generation of large voltages between different points of the film, corresponding to electric fields 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 boundary of the sample, respectively, during the out-diffusion of oxygen. The sign of the voltage is consistent with the out-diffusion of ionised O-. In order to confirm this behavior, the lateral sample geometry has been varied systematically. The observed effect promises to yield important new information on the oxygen diffusion process in the cuprates. Copyright © 1996 Elsevier Science Ltd.