Thermoelectric properties of highly textured (ZnO)5In2O3 ceramics

Abstract

Textured bulk ceramics of the layer-structured homologous compound (ZnO)5In2O3 were fabricated by the reactive templated grain growth (RTGG) technique and the thermoelectric properties evaluated. Plate-like ZnSO4·3Zn(OH)2 particles were mixed with In2O3 powders and the mixture was tape cast to form a sheet, such that the ZnSO4·3Zn(OH)2 platelets were aligned parallel to the sheet surface; the sheets were then sintered to form a single phase of (ZnO)5In2O3 with the c-axis perpendicular to the sheet surface. The electrical conductivity, σ, was found to be highly anisotropic in the textured specimen; that is, σ (in the ab-plane) > σ (along the c-axis). The textured specimen shows a porous microstructure and exhibits lower thermal conductivity than a dense ceramic specimen with random orientation. As a result, the thermoelectric figure of merit of the textured (ZnO)5In2O3 specimen is nearly three times as large as that of the randomly oriented specimen.