Improved Thermoelectric Performance of CuSbS through Gd-Substitution Induced Enhancement of Electronic Density of States and Phonon Scattering.

CuSbS has aroused great interest because of its earth-abundant constituents and intrinsic low thermal conductivity. However, the applications of CuSbS are hindered by its poor thermoelectric performance. Herein, it is shown that Gd substitution not only causes a significant increase in both electrical conductivity σ and thermopower but also leads to dramatic drop in lattice thermal conductivity . Consequently, large reaches 0.94 at 749 K for CuGdSbS, which is ∼41% higher than the value of undoped sample. Rietveld refinements of XRD results show that accompanying inhibition of impurity phase CuSbS, the number of Cu vacancies increases substantially with substituted content ( ≤ 0.3), which leads to reduced owing to intensive phonon scattering by the point defects and increased σ arising from the charged defects (). Crucially, synchrotron radiation photoelectron spectroscopy reveals substantial increment of electronic density of states at Fermi level upon Gd substitution, which is proven, by our first-principle calculations, to originate from contribution of Gd 4f orbit, resulting in enhancement of . Our study provides us with a new path to enhance thermoelectric performance of CuSbS.