Y₂Te₃: A New n‑Type Thermoelectric Material

Rare-earth chalcogenides <i>Re</i>_3–<i>x</i><i>Ch</i>₄ (<i>Re</i> = La, Pr, Nd, <i>Ch</i> = S, Se, and Te) have been extensively studied as high-temperature thermoelectric (TE) materials owing to their low lattice thermal conductivity (κ_L) and tunable electron carrier concentration <i>via</i> cation vacancies. In this work, we introduce Y₂Te₃, a rare-earth chalcogenide with a rocksalt-like vacancy-ordered structure, as a promising n-type TE material. We computationally evaluate the transport properties, optimized TE performance, and doping characteristics of Y₂Te₃. Combined with a low κ_L, multiple low-lying conduction band valleys yield a high n-type TE quality factor. We find that a maximum figure of merit <i>zT</i> > 1 can be achieved when Y₂Te₃ is optimally doped to an electron concentration of 1–2 × 10²⁰ cm^–3. We use defect calculations to show that Y₂Te₃ is n-type dopable under Y-rich growth conditions, which suppress the formation of acceptor-like cation vacancies. Furthermore, we propose that optimal n-type doping can be achieved with halogens (Cl, Br, and I), with I being the most effective dopant. Our computational results as well as experimental results reported elsewhere motivate further optimization of Y₂Te₃ as an n-type TE material.