Thermoelectric performance of codoped (Bi, In)-GeTe and (Ag, In, Sb)-SnTe materials processed by Spark Plasma Sintering

GeTe and SnTe based materials are emerging as viable alternatives for toxic PbTe based thermoelectric materials. Here, a systematic study of thermoelectric properties of Bi and In codoped GeTe, and Sb, In and Ag codoped SnTe alloys processed by Spark Plasma Sintering are presented. We report that codoping of Bi and In to GeTe, (i) enhances the thermoelectric performance by the synergistic effect of nanostructuring, suppression of carrier density and creation of resonant level, which enables to simultaneously enhance the thermopower and reduce the thermal transport, and (ii) promotes the R3m -> Fm-3m structural transition. These cumulative effects help Ge0.93Bi0.05In0.02Te to maintain the peak figure of merit, zT similar to 0.85 over a wide spectrum of temperature from 550 to 773 K, making them a serious candidate for device fabrications. We also report that Sb and In codoping in SnTe enhances the thermoelectric performance, as Sn0.845Sb0.15In0.005Te exhibits an improved zT similar to 0.8 at 823 K, when compared to pristine SnTe. (C) 2018 Elsevier B.V. All rights reserved.