Role of Bi doping in thermoelectric properties of CaMnO3

Electron-doped perovskite Ca1−xBixMnO3 (x = 0, 0.02, 0.03, 0.04, 0.06 and 0.10) was prepared by a conventional solid-state reaction method. Their homogeneity was confirmed using X-ray diffraction and their thermoelectric properties were measured up to 973 K. The results indicate that both the electrical resistivity and the absolute value of the Seebeck coefficient decrease with increasing Bi doping level; this behaviour is indicative an increase in carrier concentration with Bi content. The maximum power factor (4.67 × 10−4 W m−1 K−2) was achieved at 423 K for Ca0.97Bi0.03MnO3 which is four times larger than that of the undoped CaMnO3. The lowest thermal conductivity (1.4 W m−1 K−1) was obtained at 973 K for the same composition (x = 0.03). The maximum ZT value obtained was ∼0.25 at 973 K for x = 0.03; a threefold increase over that of undoped CaMnO3.