Development of Bi2Te2.4Se0.6 alloy for thermoelectric power generation applications

The quest for improving eco-friendly renewable energy conversion methods due to the declining resources of conventional energy reserves and a rise in environmental awareness is constantly growing. The thermoelectric method of directly converting thermal into electrical energy is attracting increased attention for such applications and thus enhancing its efficiency is of great importance. The most efficient n-type thermoelectric materials for temperatures up to 300 °C are currently Bi2TexSe3-x based. By optimizing the preparation process while considering the inherent crystallographic anisotropy, the efficiency of such materials can be further improved. In this study the Bi2Te2.4Se0.6 composition was optimized by CHI3 doping, preferred alignment of the crystallographic orientation, and lattice thermal conductivity minimization. The synthesis route included rocking furnace melting, energetic ball milling and hot pressing with optimal parameters for enhancement of the thermoelectric figure of merit, ZT, at temperatures higher than 200 °C, commonly applied in low temperature power generation applications. The transport properties in the directions parallel and perpendicular to the pressing direction were examined. In the direction perpendicular to the pressing axis, a maximal ZT of ∼0.9 was obtained at ∼175 °C, which is as far as we know among the highest ever reported for n-type Bi2TexSe3-x based alloys.