Y 2 Te 3 : A New n-Type Thermoelectric Material.

Rare-earth chalcogenides Re 3- x Ch 4 ( Re = La, Pr, Nd, Ch = 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 via cation vacancies. In this work, we introduce Y 2 Te 3 , 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 Y 2 Te 3 . 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 zT > 1 can be achieved when Y 2 Te 3 is optimally doped to an electron concentration of 1-2 × 10 20 cm -3 . We use defect calculations to show that Y 2 Te 3 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 Y 2 Te 3 as an n-type TE material.