Y2Te3: A New n-type Thermoelectric Material

Rare-earth chalcogenides Re3-xCh4 (Re = La, Pr, Nd, Ch = S, Se, Te) have been extensively studied as high-temperature thermoelectric (TE) materials owing to their low lattice thermal conductivity (kL) and tunable electron carrier concentration via 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 intrinsic transport properties, optimized TE performance, and doping characteristics of Y2Te3. Combined with a low kL, multiple low-lying conduction band valleys yield a high n-type TE quality factor. We find that a maximum figure-of-merit zT > 1.0 can be achieved when Y2Te3 is optimally doped with electron concentrations 1-2 x 10^20 cm-3. We use defect calculations to show that Y2Te3 is n-type dopable under Y-rich growth conditions, which suppresses the formation of acceptor-like cation vacancies. Furthermore, we propose that optimal n-type doping can be achieved with halogens (Cl, Br, 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.