Y2Te3: A New n-Type Thermoelectric Material

Abstract

Rare-earth chalcogenides Re_3-xCh₄ (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 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 zT > 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.

Keywords: chalcogenide; defects; dopants; electrical transport; thermoelectrics.