Enhanced Thermoelectric Performance of S-Doped AgSbTe₂ via Synergistic Optimization of Electrical and Thermal Transport

P-type AgSbTe2 exhibits great potential due to its high thermoelectric (TE) performance in the medium-temperature range. It is of importance from both scientific and application perspectives to enhance the TE performance of AgSbTe2 by substituting the environmentally harmful and expensive Te with the eco-friendly and cost-effective element S. In this work, we report an enhanced maximum figure of merit zT value of 1.31 at 573 K and an average zT value of 0.87 in the temperature range of 300–623 K for S-doped AgSbTe2, which are increases of about 23% and 30% than those of the undoped sample through the synergistic optimization of the electrical and thermal transport properties. S dopant suppresses the formation of Ag2Te precipitates at the grain boundaries, increases the p-type carrier concentration, and enlarges effective mass, which promotes the power factor. Meanwhile, the thermal conductivities of AgSbTe2–xSx samples decrease due to enhanced phonon scattering caused by S doping. This work demonstrates that the eco-friendly and low-cost substitution for Te with S is promising to advance the applications of AgSbTe2-based TE materials.