Effects of substituting La3+, Y3+ and Ce4+ for Ca2+ on the high temperature transport and thermoelectric properties of CaMnO3

摘要

We report the high temperature transport and thermoelectric properties of Ca1-xRxMnO3 (R = La, Y and Ce) perovskites in the electron-doped range. The substitution of different valence ions has a similar effect on the thermoelectric properties of this system. Resistivity and thermopower change regularly as the enhancement of doping level; they are both determined mainly by electron concentration. Thermal conductivity is dependent mainly on the weight of R ions, and it decreases monotonically with increasing doping content. The optimal electron concentration is around 0.1-0.12 for thermoelectric performance; in this range the ZT value of Ca0.9La0.1MnO3 exceeds 0.12 at 1000 K, exhibiting a good high temperature thermoelectric applied potential. Besides, the hopping nature of the charge carriers is well explained in the framework of polaron theory. The high temperature thermopower values which are inconsistent with nominal Mn3+ ion t(2g)(3)e(g)(1) configuration are also discussed.