Ultrahigh thermoelectricity obtained in classical BiSbTe alloy processed under super-gravity.

Abstract

Thermoelectric materials allow direct conversion between heat and electricity and may be useful for power generation or solid-state refrigeration. However, improving thermoelectric performance is challenging because of the strong coupling between the electrical and thermal transport properties. We demonstrate a new super-gravity-field re-melting fabrication technology that synergistically optimizes the thermoelectric performance. Using a super-gravity field, the brittle (Bi,Sb)₂Te₃ alloy undergoes unusual plastic deformation and forms mounts of microstructure defects, which is rarely observed in common fabrication process. As a result, the microstructure reconstruction and carrier concentration optimization were simultaneously realized, resulting in an ultra-low lattice thermal conductivity of <0.25 W/m K and a record-high figure of merit of >1.91 in the BiSbTe alloy. The strong enhancement of thermoelectric properties was validated in a thermoelectric module with high conversion efficiency of 6.4% and corresponding output power density of 0.34 W/cm² when subjected to a temperature difference of 185 K. This work highlights a new super-gravity strategy to achieve a high thermoelectric performance, which may be applicable to other thermoelectric materials.