Thermoelectric properties of CaMnO3 system

Ca_1-xRE_xMnO₃ (RE: Nd, Tb, Ho, Yb, Lu, x = 0.1 and 0.2) bulks were prepared by a solid state reaction. They show metallic behavior at temperatures higher than about 400 K and electrical resistivity rho is lower than 12 mOmega cm at 1000 K in air. Absolute values of Seebeck coefficient S increases with temperature up to 973 K for all samples except Ca_0.9Yb_0.1MnO₃ at 973 K. For Ca_0.9Lu_0.1MnO₃, S value reaches -130 muV/K at 973 K. Both thermoelectric properties are dominated mainly by crystallographic structure. Power factor PF (=S²/rho) increases with decreasing cell volume. Thermal conductivity kappa of Yb- and Lu-substituted samples is as low as 1.5 W/m-K² and dimension-less figure of merit ZT reaches 0.16 at 973 K for Ca_0.8Lu_0.2MnO₃ in air.