Boosting Thermoelectric Performance of SnTe by Selective Alloying and Band Tuning

SnTe-based compounds have attracted increasing attention in recent years as lead-free thermoelectric materials. However, the thermoelectric performance of pristine SnTe is poor because of its overhigh lattice thermal conductivity and low Seebeck coefficient. In this study, we demonstrate that SnSe alloying considerably frustrates heat conduction in SnTe while preserving high charge carrier mobilities, by taking GeTe alloying as a comparative study. Based on these findings, we proceed to substitute Sn atoms by Cd in SnTe-SnSe alloys. This proves to be an efficient way of converging the two valence bands of SnTe, leading to remarkably improved Seebeck coefficients with the highest value approaching 200 mu V/K at elevated temperatures. Consequently, the thermoelectric dimensionless figure of merit ZT reaches similar to 0.9 at 873 K for the sample with nominal composition of Sn0.96Cd0.04Te0.88Se0.12, which is over 60% improvement over pristine SnTe. Our work highlights the importance of selective alloying and band tuning in engineering bulk thermoelectric materials. (c) 2022 Elsevier Ltd. All rights reserved.