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.