DC electrical resistivity (r) and thermoelectric power (TEP) of La0.7xBixSr0.3MnOy (x=0, 0.05, 0.1, 0.15, 0.2, 0.25
and 0.3 at%) manganites have been studied. The resistivity of the samples shows a metal–semiconductor (insulator)
transition for xX0.2. For x=0.25 and 0.3 at%, the compounds exhibit semiconducting behavior down to T=83 K. The
TEP for xp0.2 at% is of positive sign above the transition temperature (Tm); it decreases below Tm and has changed
sign for T4300 K. The replacement of the La ion by Bi ion results in a reduction of transition temperature (Tm) (M–S
transition) and increasing the value of both r and TEP. The value of resistivity activation energy (Er) and TEP
activation energy (Es) calculated above Tm.