Non-equilibrium strategy for enhancing thermoelectric properties and improving stability of AgSbTe₂

Inorganic thermoelectrics have progressed in leaps and bounds in the recent years. This is largely driven by the advancements in both physical understanding coupled with structural properties. In particular, p-type AgSbTe₂ has recently emerged as one of the best thermoelectric materials for low and medium temperature applications. Nevertheless, it suffers from longstanding stability and inconsistency problems, which results in n-type Ag₂Te precipitates and drastic deterioration in performance. In this work, we trace the origin of the variability of thermoelectric properties of AgSbTe₂ found in literatures to the cooling rate during synthesis. Furthermore, we demonstrate a non-equilibrium annealing strategy to achieve consistent properties. Ultimately, a peak zT of 1.15 at 623 K was achieved for optimally annealed and quenched pristine AgSbTe₂. Importantly, in the absence of dopant to fully stabilize the AgSbTe₂ phase, we propose limiting its application to the vicinity of room temperature for cooling, and above 633 K for waste heat harvesting.