Electrical resistivity and thermopower of(La1-xSrx)MnO3 and (La1-xSrx)CoO3at elevated temperatures

Electrical resistivity and Seebeck (S) measurements were performed on (La1- xSrx)MnO3 (0.02 less than or equal to x less than or equal to 0.50) and (La 1-xSrx)CoO3 (0 less than or equal to x less than or equal to 0.15) in air u p to 1073 K. (La1-xSrx)MnO3 (x less than or equal to 0.35) showed a metal-t o-semiconductor transition; the transition temperature almost linearly incr eased from similar to 250 to similar to 390 K with increasing Sr content. T he semiconductor phase above the transition temperature showed negative val ues of S. (La1-xSrx)CoO3 (0 less than or equal to x less than or equal to 0 .10) showed a semiconductor-to-metal transition at similar to 500 K. Domina nt carriers were holes for the samples of x greater than or equal to 0.02 a bove room temperature. LaCoO3 showed large negative values of S below ca. 4 00 K, indicative of the electron conduction in the semiconductor phase. (C) 2000 Elsevier Science Ltd. All rights reserved.