Transport Properties Of Manganese Perovskites Bi1-Xcaxmno3 (0.7 <= X <= 0.95)

We report the temperature dependence of electrical resistivity and thermoelectric power of the manganese perovskites Bi1-xCaxMnO3 (0.7 <= x <= 0.95). The resistivity for x = 0.75 and 0.7 is well fitted with rho proportional to exp(1/T)((1/4)) below the charge-ordering temperatures (T-co). The temperature dependence of thermoelectric power for samples with x = 0.8, 0.75 and 0.7 shows the rapid decrease below T-co. In the lower temperatures than T-co, it goes through minimum and absolute thermoelectric power decreases and tends to change the sign. The activation energy was estimated as 57, 64, 148 meV for x = 0.8, 0.75, 0.7 from the linear fits in the form S - 1/T plots. The activation energy increases with decreasing the Ca content in the Bi1-xCaxMnO3 system.