Attaining high mid-temperature performance in (Bi,Sb)(2)Te-3 thermoelectric materials via synergistic optimization

For decades, zone-melted Bi2Te3-based alloys have been the most widely used thermoelectric materials with an optimal operation regime near room temperature. However, the abundant waste heat in the mid-temperature range poses a challenge; namely, how and to what extent the service temperature of Bi2Te3-based alloys can be upshifted to the mid-temperature regime. We report herein a synergistic optimization procedure for Indium doping and hot deformation that combines intrinsic point defect engineering, band structure engineering and multiscale microstructuring. Indium doping modulated the intrinsic point defects, broadened the band gap and thus suppressed the detrimental bipolar effect in the mid-temperature regime; in addition, hot deformation treatment rendered a multiscale microstructure favorable for phonon scattering and the donor-like effect helped optimize the carrier concentration. As a result, a peak value of zT of similar to 1.4 was attained at 500 K, with a state-of-the-art average zT(av) of similar to 1.3 between 400 and 600 K in Bi0.3Sb1.625In0.075Te3. These results demonstrate the efficacy of the multiple synergies that can also be applied to optimize other thermoelectric materials.