Figure shows the convex hull formed by the stable competing phases in the binary Y-Te chemical space. The allowed range of ∆µ Y and ∆µ Te for the phase stability is set by the two-phase equilibrium of Y 2 Te 3 with either YTe 3 or YTe (Table ). Here, the equilibrium between Y 2 Te 3 and YTe 3 is denoted as "most Ypoor" condition since Y 2 Te 3 is stable under these thermodynamic conditions despite being compositionally Y-deficient. In a similar fashion, the two-phase equilibrium with YTe is denoted as the Under the most Y-poor condition (Figure ), Y 2 Te 3 is an intrinsic semiconductor with the equilibrium Fermi energy (E F,eq ) pinned near mid-gap, yielding a net hole concentration of 1.1 × 10 16 cm -3 at T = 923 K, which is the typical solid-state synthesis temperature. We find that Y 2 Te 3 cannot be doped n-type under Y-poor conditions because the low formation energy of acceptorlike cation vacancies (V Y ) indicates that electrons generated by a donor dopant will be charge compensated by the holes produced by V Y . Similarly, it will be difficult to dope Y 2 Te 3 p-type under Y-poor conditions due to the low formation energy of the amphoteric anti-site defect Te Y . At Fermi energies closer to the valence band, Te Y acts as a singly-charged donor defect such that holes introduced by an extrinsic p-type dopant will be charge compensated by the electrons from Te Y . As a result, we predict that it will be difficult to dope Y 2 Te 3 either n-or p-type under Y-poor conditions, and will remain an intrinsic semiconductor with low free carrier concentrations.