Mechanisms behind the weighted mobility improvement in FeTe2-CoTe2 thermoelectric solid solution alloys

초록

Fe-based dichalcogenides, captivating interest for their narrow 3d bands and potential as thermoelectric materials, have recently garnered attention. Park et al. reported enhanced zT of 0.18 for (Fe1-xCox )Te2 (x = 0.5) at 600 K, attributing it to the emergence of a fat band near the Fermi level. However, the infuence of alloying-induced band engineering and point defect-mediated phonon scattering remains elusive. Herein, we investigate the impact of compositional variation (x) on elec- tronic transport properties using the Single Kane Band model. Our analysis reveals predominant band convergence (x < 0.5) transitioning to band sharpening (x > 0.5). Notably, the weighted mobility, directly linked to the theoretical maximum power factor, exhibits a pronounced increase with increasing x. To evaluate the strength of phonon scattering by point defects, the Callaway-von Baeyer (CvB) model was employed. Surprisingly, the highest scattering parameter was not observed at x = 0.5 (maximum mixing) but at x = 0.25 and 0.75, signifying stronger phonon scattering at these compositions. Finally, considering the weighted mobility and lattice thermal conductivity, the theoretical maximum zT was calculated. Our fndings predict a potential enhancement of 118 times in zT for x = 0.75 (0.68) compared to the experimental value at x = 0 (0.005). This study underscores the signifcant potential for discovering novel, unexplored metal chalcogenide-based solid solutions with enhanced thermoelectric performance.

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