High thermoelectric performance by resonant dopant indium in nanostructured SnTe

TLDR

Lead‑free SnTe is attractive for waste‑heat recovery, but its figure‑of‑merit must approach that of lead chalcogenides. The study investigates whether indium doping can create resonant levels that dramatically increase the Seebeck coefficient of nanostructured SnTe. Resonant levels from indium impurities inside the valence band, confirmed by first‑principles simulations, explain the enhanced Seebeck coefficient. Indium doping, together with reduced grain size from ball milling and hot pressing, raised the peak ZT to ~1.1 at 873 K and improved average ZT.

Abstract

From an environmental perspective, lead-free SnTe would be preferable for solid-state waste heat recovery if its thermoelectric figure-of-merit could be brought close to that of the lead-containing chalcogenides. In this work, we studied the thermoelectric properties of nanostructured SnTe with different dopants, and found indium-doped SnTe showed extraordinarily large Seebeck coefficients that cannot be explained properly by the conventional two-valence band model. We attributed this enhancement of Seebeck coefficients to resonant levels created by the indium impurities inside the valence band, supported by the first-principles simulations. This, together with the lower thermal conductivity resulting from the decreased grain size by ball milling and hot pressing, improved both the peak and average nondimensional figure-of-merit ( ZT ) significantly. A peak ZT of ∼1.1 was obtained in 0.25 atom % In-doped SnTe at about 873 K.