Optimizing thermoelectric performance of SnTe via alloying with AgSnSe2 and PbTe

Eco-friendly SnTe is considered as one of the potential candidates to replace PbTe for thermoelectric applications. Unfortunately, pristine SnTe possesses a relatively high thermal conductivity, which is detrimental for its performance. Generally, introducing additional phonon scattering through atomic disorder is a simple and reliable method to suppress the thermal conductivity of a material. However, the strong disorder is usually harmful for the electrical conductivity. In this study, we attempted to simultaneously optimize the electrical conductivity and thermal conductivity of SnTe. A strong atomic disorder was introduced via alloying with AgSnSe2, which decreased the thermal conductivity significantly. Also, AgSnSe2 showed a donor behavior in the AgSnSe2-alloyed SnTe; the increased carrier concentration compensated for the decrease in the carrier mobility and rendered a good electrical conductivity in the alloyed samples. Based on the experimental data, (SnTe)0.95(AgSnSe2)0.05 shows the best thermoelectric performance. To further improve the performance, lead (Pb) was substituted for Sn in (SnTe)0.95(AgSnSe2)0.05, and (Sn0.875Pb0.125Te)0.95(AgSnSe2)0.05 achieved the ZT of 0.86 at 600 °C.