High temperature thermoelectric properties of Ca1-xDyxMnO2.98 (x=0, 0.05, 0.10, 0.15, 0.20) have been measured in the temperature range from 300 to 1273K. Ca1-xDyxMnO2.98 (x=0.10, 0.15, 0.20) exhibited the metal-insulator transition in the relation between electrical resistivity and temperature, and the transition temperature increased with increasing x. Electrical resistivity in the metallic region decreased with increasing x content, reflecting the increase of Mn3+ ions, and the absolute value of Seebeck coefficient (α) also decreased. Thermal conductivity (λ) did not considerably change with increasing x content. Among substituted CaMnO3, the highest figure of merit of Z=1.05×10-4K-1 was obtained for x=0.05 and 0.10 at 773K, while a Z=1.63×10-4K-1 was obtained for x=0.20 at 1273K.
2003 The Ceramic Society of Japan