Thermoelectric Properties of (In, Cr) 2 Ge 2 Te 6 Layered Compounds

Abstract

Ternary layered compounds belonging to the M 2 N 2 Q 6 family have recently garnered considerable attention owing to their compositional diversity and intrinsically low thermal conductivity. In this work, we systematically investigate the crystal structures and thermoelectric properties of layered (In, Cr) 2 Ge 2 Te 6 compounds by combining experimental characterizations with first-principles calculations. Cr 2 Ge 2 Te 6 compound exhibits stronger structural anisotropy, a narrower band gap, and higher thermoelectric performance than In 2 Ge 2 Te 6 . Both materials show ultralow lattice thermal conductivity, originating from their low sound velocities and pronounced atom vibration coupling.Moreover, alloying In 2 Ge 2 Te 6 with Cr 2 Ge 2 Te 6 effectively strengthens the point-defect phonon scattering, leading to further reduced lattice thermal conductivity and improved thermoelectric performance. Notably, InCrGe 2 Te 6 exhibits a lattice thermal conductivity as low as 0.85 W m -1 K -1 near room temperature and drops to 0.43 W m -1 K -1 at 750 K, leading to a maximum zT value of 0.38. Further optimization of the carrier concentration is expected to yield higher thermoelectric performance.