Band convergence and nanostructure modulations lead to high thermoelectric performance in SnPb0.04Te-y% AgSbTe2

Abstract

SnTe is a lead-free and promising mid-temperature thermoelectric material while its performance is largely hindered owing to the relatively high hole carrier concentration originating from the existence of extraordinary Sn vacancies in intrinsic SnTe. In this study, we firstly introduced excess Pb into SnTe matrix to compensate the Sn vacancies, leading to the greatly decreased carrier concentration. Then, we found that the ternary compound AgSbTe2 plays synergistic roles in optimizing the thermoelectric transport properties of SnTe. Namely, alloying AgSbTe2 can induce the electronic band convergence and band flattening in SnTe, leading to the significantly enhanced band effective mass (m∗) and Seebeck coefficient. Additionally, alloying AgSbTe2 produces plentiful Ag-rich nanoprecipitates, which strengthens the scattering of phonons, leading to the lowest lattice thermal conductivity of ∼0.47 Wm−1K−1. By this stepwise strategy, an outstanding ZT value ∼1.1 can be attained at 823 K for the SnPb0.04Te–12%AgSbTe2 sample, while an average ZT can be obtained ∼ 0.72 from 400 K to 800 K for sample SnPb0.04Te-12%AgSbTe2. Our study further reveals the great potential for SnTe as promising thermoelectrics.