Boosting the thermoelectric performance of SnTe through localized van der Waals gap construction and configurational entropy engineering

Abstract

SnTe, as an environmentally friendly lead-free p-type thermoelectric material, is deemed to have potential applications in the medium temperature range (500–900 K); however, the thermoelectric performance of SnTe materials is limited by intrinsic characteristics such as the low formation energy of Sn vacancies, the low degeneracy of valence bands, and relatively high lattice thermal conductivity. In this study, we begin by alloying non-stoichiometric Ag_1−δSb_1+δTe_2+δ to construct localized van der Waals (vdWs) planar gaps for reducing the lattice thermal conductivity, and then configurational entropy engineering is adopted to optimize its valence band structure. Simultaneously, increasing configurational entropy results in aggravated lattice distortion and consequently a reduced lattice thermal conductivity. Ultimately, we achieved a decent maximal figure of merit ZT of ∼1.23 at 623 K and an outstanding average ZT of ∼0.96 in the temperature range of 323–823 K; remarkably, the room-temperature ZT reaches as high as ∼0.38, which is one of the highest values reported to date. The findings in this study might shed light on future research on SnTe and related material systems.