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.