Post‑Extrusion Annealing Enhances Thermoelectric Performance of Hot‑Extruded p‑Type Bi0.3Sb1.7Te3

Bismuth telluride Bi2Te3-based alloys are currently the most widely used near-room-temperature thermoelectric materials. However, the poor mechanical properties of the zone melting (ZM) method and the inferior electrical properties of the powder metallurgy method have limited their further applications. In this study, p-type Bi0.3Sb1.7Te3 polycrystalline bulk materials were prepared by the hot extrusion (HE) combined with well-tuned heat treatment. Three different routes were compared: annealing prior to hot extrusion (AN+HE), hot extrusion followed by annealing (HE+AN), and a combination of pre‑extrusion annealing, hot extrusion, and post‑extrusion annealing (AN+HE+AN). Among the three routes, the HE+AN sample exhibits the highest Seebeck coefficient of 212 μV K-1 and the highest power factor of 61.5 μW cm-1K-2, leading to a maximum thermoelectric figure of merit ZT of 1.28 for p-type materials at room temperature. This outstanding performance is attributed to the effective elimination of deformation‑induced antisite defects during post‑extrusion annealing, which simultaneously reduces the carrier concentration and enhances the carrier mobility. These results demonstrate that the post‑extrusion annealing step is indispensable to achieve a microstructure with minimal defects and optimized texture, making it a promising route for high‑performance p‑type bismuth telluride thermoelectrics.