where C p = 7/2 k B is the constant-pressure heat capacity for a diatomic molecule assuming an ideal gas behavior, S 0 = 205 J mol -1 K -1 , 76 k B is the Boltzmann constant and p 0 O 2 is the partial pressure under standard conditions i.e., p 0 O 2 = 1 atm. In order to suppress the formation of Y 2 O 3 at a given temperature (T ), p O 2 should be lower than the value fixed by the three-phase equilibrium regions. Our analysis shows that, at 1000 K, p O 2 must be lower than at least 3.3 × 10 -27 atm (Y-poor condition) to prevent the formation of Y 2 O 3 . Such low oxygen partial pressure is currently not achievable even in ultra-high vacuum systems (10 -13 atm), suggesting oxidation of Y 2 Te 3 is imminent. However, the above analysis assumes thermodynamic equilibrium, whereas oxidation is often kinetics and diffusion-limited. It is possible that surface oxidation will protect the bulk from further oxidation, as is observed in other chalcogenide-based thermoelectric materials e.g., SnSe and Sc 2 Te 3 . Therefore, we recommend that future experimental studies of Y 2 Te 3 pay close attention to the pres-ence of oxide inclusions in the bulk, as reproducibility has proven difficult in oxidized rare-earth thermoelectric materials such as La 3-x Te 4 .