Entropy Engineering Realized Ultralow Thermal Conductivity and High Seebeck Coefficient in Lead-Free SnTe

Tin telluride is a promising lead-free IV–VI thermoelectric compound, while its intrinsic high thermal conductivity limits the further improvement of performance. In this work, the strategy of high-entropy engineering is implemented to reduce the thermal conductivity of SnTe. To increase the configuration entropy of the compound, the solid solutions of (AgxSbxSn1–2x)(SxSexTe1–2x) are successfully synthesized. In (Ag0.15Sb0.15Sn0.7)(S0.15Se0.15Te0.7), the obtained thermal conductivity reaches a very low value of 1.27 W m–1 K–1 at 300 K, which is 85% reduced relative to the pristine SnTe. In spite of the increase of carrier concentration, the Seebeck coefficients of solid solutions are enlarged, originating in the distortion of electron density of states. Finally, the maximum ZT value of 1.02 is reached in (Ag0.15Sb0.15Sn0.7)(S0.15Se0.15Te0.7) at 850 K. This work suggests that high-entropy engineering is an effective strategy for thermoelectric materials.