Anisotropic thermoelectric properties of crystal-axis oriented ceramics oflayer-structured oxide in the Ca-Co-O system

Anisotropic thermoelectric properties of crystal-axis oriented polycrystals of layer-structured oxide in the Ca-Co-O system was discussed. Plate-like particles of (Ca2.7Bi0.3) (Co3.7Cu0.3)O9+delta were synthesized. To improve the thermoelectric properties, a c-axis oriented polycrystal of (Ca2.7Bi0. 3) (Co3.7Cu0.3)O9+delta was successfully fabricated by uniaxial-pressing an d sintering. The electrical conductivity along the ab-plane was about four times larger than that along the c-axis, while the Seebeck coefficients wer e similar. The thermal conductivity along the ab-plane was more than two ti mes larger than that along the c-axis. The resulting figure-of-merit along the ab-plane was enhanced due to the enhanced electrical conductivity.