Hot deformation induced bulk nanostructuring of unidirectionally grown p-type (Bi,Sb)2Te3 thermoelectric materials

Abstract

Nanostructuring has proved effective in improving the figure of merit in the widely used Bi₂Te₃ based thermoelectric materials. In this work, a hot deformation induced in situ nanostructuring process is directly applied to the commercial unidirectionally grown p-type Bi_0.5Sb_1.5Te₃ ingots to explore the possibility of commercial application of the “top down” nanostructuring approach, and the thermoelectric properties are investigated over a wide temperature range of 15 K to 520 K. In comparison to the commercial zone melted ingot and the hot pressed sample, it is found that the hot deformed samples exhibit much less texture and significantly reduced lattice thermal conductivity due to in situ formed nanostructures and defects. A high ZT of ∼1.3 is achieved near room temperature, ∼50% improvement compared to that of the zone melted ingot. The hot deformation process thus provides a promising top down approach to prepare high performance Bi₂Te₃ based thermoelectric materials in a way that is more readily incorporated into the existing procedure of device manufacturing.