Anisotropic Thermoelectric Properties of Crystal-Axis Oriented Ceramics of Layer-Structured Oxide in the Ca-Co-O System

Abstract

Anisotropic thermoelectric properties of crystal-axis oriented polycrystals of layer-structured oxide in the Ca-Co-O system was discussed. Plate-like particles of (Ca_2.7Bi_0.3) (Co_3.7Cu_0.3)O_9+δ were synthesized. To improve the thermoelectric properties, a c-axis oriented polycrystal of (Ca_2.7Bi_0.3) (Co_3.7Cu_0.3) O_9+δ was successfully fabricated by uniaxial-pressing and sintering. The electrical conductivity along the ab-plane was about four times larger than that along the c-axis, while the Seebeck coefficients were similar. The thermal conductivity along the ab-plane was more than two times larger than that along the c-axis. The resulting figure-of-merit along the ab-plane was enhanced due to the enhanced electrical conductivity.