Enhanced thermoelectric performance in AgSbTe₂ with extremely low thermal conductivity via grain boundary defects.

This article focuses on enhancing the thermoelectric (TE) performance of AgSbTe₂ by Fe doping to optimize electrical conductivity and reduce lattice thermal conductivity through grain boundary defect engineering. The Fe-doped AgSbTe₂ exhibits a synergistic effect where grain boundary trapping states enable thermally activated carrier release and an energy filtering effect, resulting in a high power factor and a 33% reduction in glass-like thermal conductivity. This leads to a peak dimensionless figure of merit (zT) of 1.8 at 623 K and an average zT of 1.4 between 323–623 K, marking significant improvement over the pristine material. Additionally, nickel (Ni) was identified as an effective contact layer material due to its matched thermal expansion coefficient and low interfacial resistivity, enabling single-leg TE devices with approximately 10% conversion efficiency. The study provides insights into defect engineering and device fabrication strategies for mid-temperature TE applications using lead-free AgSbTe₂-based materials.