Bi-doping effects on the transport properties in La0.7-xBixSr0.3MnOy

DC electrical resistivity (p) and thermoelectric power (TEP) of La0.7-xBixSr0.3MnOy (x = 0, 0.0 5, 0.1, 0.15, 0.2, 0.2 5 and 0.3 at%) manganites have been studied. The resistivity of the samples shows a metal-semiconductor (insulator) transition for x greater than or equal to 0.2. For x = 0. 25 and 0. 3 at%, the compounds exhibit semiconducting behavior down to T = 8 3 K. The TEP for x less than or equal to 0.2 at% is of positive sign above the transition temperature (T-m); it decreases below T-m and has changed sign for T > 300 K. The replacement of the La ion by Bi ion results in a reduction of transition temperature (T-m) (M-S transition) and increasing the value of both rho and TER The value of resistivity activation energy (E-rho) and TEP activation energy (E-s) calculated above T-m. (C) 2004 Elsevier B.V. All rights reserved.