THERMOPOWER OF YBA2CU3O7-X, ERBA2CU3O7-X

Resistance and absolute thermopower of high-Tc oxide superconductors RBa2Cu3O7-x (R=Y,Er) synthesized by a hot-press sintering technique have been measured in the temperature range of 4300 K. Resistive behavior of all samples is found to be metallic. The thermopower for both compositions is positive above the superconducting transition temperature. The thermopower of as-prepared ErBa2Cu3O7-x samples shows a weak temperature dependence with a negative slope near room temperature, which increases in magnitude as Tc is approached from above. No strong thermopower peak just above Tc has been observed either in YBa2Cu3O7-x or ErBa2Cu3O7-x. Reannealing of an ErBa2Cu3O7-x sample at 500°C for 12 h in flowing oxygen increases the magnitude of the thermoelectric power and the magnitude of its slope without affecting Tc. Comparison of the results with available theory indicates that there is no completely satisfactory theory of electrical transport in these superconducting oxides. © 1990 The American Physical Society.