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

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(Sn_1-xGe_xTe)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 ZT_max of ∼1.3 at 723 K and an excellent average ZT value of ∼0.78 at 323-773 K are simultaneously realized in Sb₂Te₃(Sn_0.8Ge_0.2Te)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 ZT_ave compounds in the future.