Probing an enhanced anisotropy Seebeck coefficient and low thermal conductivity in polycrystalline Al doped SnSe nanostructure

Abstract

Recently, SnSe based thermoelectric materials attained much interest due to their environment friendly IV–VI semiconductor group. Herein, Al doped SnSe (Sn1−xAlxSe) specimens were prepared by combined ball milling and spark plasma sintering. High resolution transmission electron microscopy analysis of (Sn1−xAlxSe) nanostructure samples confirmed the existence of different crystal defects and dislocation induced by Al doping. Lower thermal conductivity (0.63 W/mK at 750 K) is observed for Sno.92Al0.08Se samples than pristine SnSe (1.14 W/mK at 750 K), which is mainly attributed to various crystal defects, such as lattice dislocation, stacking fault, grain boundary scattering, and excellent anharmonic bonding nature of SnSe. The maximum electrical conductivity is observed for the SAS-2 sample, which correlates well with the low activation energy of 0.20 eV. The minimal doping of Al (SAS-2) decoupled the strong interdependency of electrical and thermal transport properties, leading to a maximum ZT of 0.18 at 743 K. The Al doped SnSe (Sn1−xAlxSe) induced point defects in the sample, which provides a new strategy for waste heat recovery.