Microstructural Manipulation for Enhanced Average Thermoelectric Performance: A Case Study of Tin Telluride

Abstract

Achieving a high average figure of merit in a low-cost/toxic compound, tin telluride (SnTe), is crucial for thermoelectric applications. Introducing gap-like structures into the rock–salt matrix once elucidated a large potential; however, the poor quantity and controllability of the planar defects become the drawbacks. Here, we demonstrate, by electron microscopy and X-ray diffraction, that dense planar cationic vacancies can be produced in Sb2Te3(Sn1–xGexTe)8 samples for the first time, leading to an effective targeted solution. On the basis of the optimized lattice matrix, a low room-temperature lattice thermal conductivity of ∼0.7 W m–1 K–1 (25% of pristine SnTe) can be achieved. Additionally, the first-principles calculation result reveals that the value of density-of-state effective mass is increased after manipulating the local cation matrix, resulting in an outstanding power factor of ∼2.5 mW m–1 K–2 at 723 K when x = 0.2. Eventually, a competitive maximum figure of merit ZTmax of ∼1.3 at 723 K and an excellent average ZT value of ∼0.78 at 323–773 K are simultaneously realized in Sb2Te3(Sn0.8Ge0.2Te)8. This pioneered study about manipulating gap-like structures and its effects on the transport properties of SnTe-based materials would also provide a promising alternative for pursuing other high ZTave compounds in the future.