Improved thermoelectric performance of (Fe,Co)Sb3-type skutterudites from first-principles
Winnie K. Wong-Ng, Izaak Williamson, Logan J. Her, Xianli Su, Yonggao Yan, Lan Li
Skutterudite materials have been considered as promising thermoelectric candidates due to intrinsically good electrical conductivity and tailorable thermal conductivity. Options for improving thermal-to-electrical conversion efficiency include identifying optimal materials, adding filler atoms, and substitutional dopants. Incorporating filler or substitutional atoms in the skutterudite compounds can enhance phonon scattering, resulting in reduction of thermal conductivity, as well as improving electrical conductivity. The structures, electronic properties, and thermal properties of double-filled Ca0.5Ce0.5Fe4Sb12 and Co4Sb12-2xTexGex compounds (x = 0, 0.5, 1, 2, 3, and 6) have been studied using density functional theory-based calculations. Both Ca/Ce filler atoms in FeSb3 and Te/Ge substitution in CoSb3 cause a decrease in lattice constant for the compounds. As Te/Ge substitution concentration increases, lattice constant decreases and structural distortion of pnicogen rings in the compounds occurs. This indicates a break in cubic symmetry of the structure. The presence of fillers and substitutions causes an increase in electrical conductivity and a gradual decrease in electronic band gap. A transition from direct to indirect band-gap semiconducting behavior is found at x = 3. Phonon density of states for both compounds indicate phonon band broadening by the incorporation of fillers and substitutional atoms. Both systems are also assumed to have acoustic-mode-dominated lattice thermal conductivity. For the Co4Sb12-2xTexGex compounds, x = 3 has the lowest phonon dispersion gradient and lattice thermal conductivity, agreeing well with experimental measurements. Our results exhibit the improvement of thermoelectric properties of skutterudite compounds through fillers and substitution.
, Williamson, I.
, Her, L.
, Su, X.
, Yan, Y.
and Li, L.
Improved thermoelectric performance of (Fe,Co)Sb3-type skutterudites from first-principles, Journal of Applied Physics, [online], https://doi.org/10.1063/1.4940952
(Accessed December 4, 2023)