Boosting the thermoelectric properties of layered SnSb2Te4 compound by microstructure regulation combined with heterovalent halogen substitution

The layered IVV2Te4-based compounds have recently received significant attention due to their intrinsically low lattice thermal conductivities. However, the influence of microstructure regulation and halogen doping on their thermoelectric properties has been scarcely studied. In this work, we systematically investigated the anisotropic thermoelectric transport properties of pristine SnSb2Te4 compounds with varied microstructures manipulated by ball milling. With the help of thermoelectric transport models, the optimal ball milling time is estimated based on the calculation of quality factor. Furthermore, the remarkably improved Seebeck coefficient is achieved by the introduction of halogen elements into Te sites, which is attributed to reduced carrier concentration and converged carrier pockets. As a result, a maximal zT ∼0.4 at 725 K is achieved in SnSb2(Te0.94I0.06)4 sample aligned with the SPS pressure direction with a ball-milling time of 1 h, which demonstrates a 35% enhancement over the pristine sample. This work provides an insightful guide to elevate the thermoelectric properties of layered IVVI2Te4-based compounds.