Mechanistic Insights into Surface Oxidation and Oxygen Diffusion in Bismuth Telluride Thermoelectrics

The thermal stability of bismuth telluride (Bi 2 Te 3 ) nanoparticles, a benchmark bismuth-chalcogenide thermoelectric material, critically depends on the coupled effects of surface reactions and oxygen transport. Through integrated thermal, structural, and microscopic analyses, this work establishes a detailed mechanistic understanding of the oxidation-driven degradation of Bi 2 Te 3 in various environments. The results reveal a sequential transformation pathway in which initial surface chemisorption and oxide nucleation form a compact passivating layer, shifting the process from surface-controlled to diffusion-controlled oxidation. At elevated temperatures, the sublimation of Te creates nanoscale defects and channels that enhance oxygen transport, thereby reestablishing surface-oxidation-controlled kinetics and accelerating degradation. High resolution transmission electron microscopy (HRTEM) analysis provided direct nanoscale evidence of oxide phase evolution, defect formation, and interface restructuring, validating the proposed mechanism. Kinetic modeling further supports these observations by correlating changes in activation energy ( E α ) with transitions between surface- and diffusion-limited regimes. Overall, this study offers mechanistic insights into oxygen-mediated degradation pathways that influence the operational stability and performance of Bi 2 Te 3 -based thermoelectric materials in energy-conversion applications.