A two-step synthesis process of thermoelectric alloys for the separate control of carrier density and mobility

Abstract

It is challenging to improve the thermoelectric figure-of-merit as its constituent terms such as Seebeck coefficient, electrical conductivity, and thermal conductivity, are inter-related in the way that the enhancement of one term leads to the degradation of others. Therefore, it is highly desirable to design a new synthesis process that allows us to independently control these terms. Here, we report a simple, two-step process combining spark plasma sintering (SPS) and post-annealing (PA) to separately control the carrier density and mobility in the p-type (Bi0.2Sb0.8)(2)Te-3. High-temperature SPS enables enhancing the carrier mobility by reducing scattering sites such as grain boundaries. Then, the following PA at a lower temperature allows tailoring the carrier density without the degradation of mobility. Beyond bismuth telluride-based, room-temperature thermoelectric materials, we believe that our result will provide an insight for the performance enhancement of other thermoelectric materials such as oxide and skutterudite. (C) 2017 Elsevier B.V. All rights reserved.