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. We find that Y2Te3 exhibits low kL in agreement with previous experiments. Combined with a large conduction band (CB) degeneracy, Y2Te3 has a high n-type TE quality factor. Interestingly, our electronic structure calculations reveal the presence of multiple low-lying conduction band valleys, which opens opportunities for further improvement of TE performance through band convergence. 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 degenerate 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 make the case for further optimization of Y2Te3 as a n-type TE material.