Ultra-low lattice thermal conductivity and superior electronic transport properties endow high thermoelectric performance in Sn0.5Pb0.5O oxide-based superlattice

Abstract

Inspired by recent experimental synthesis of prototypical Sn(1−x)Pb(x)O under ambient and high-temperature conditions, we systematically construct layered Sn(1−x)Pb(x)O alloys across a range of compositions. Herein, we study the thermoelectric properties of layered Sn(1−x)Pb(x)O compositions using the first-principles-based density functional theory and density functional perturbation theory calculations. Our results show that Sn(1−x)Pb(x)O compositions exhibit very low lattice thermal conductivity (κl) of 2.94 and 1.83 W/m K for x = 0.5 and 1, respectively, at 300 K. Such remarkably low κl of Sn0.5Pb0.5O and PbO primarily originates from pronounced phonon softening and coupling of phonon branches driven by the presence of mass anisotropy and symmetry breaking induced by Pb substitution. Furthermore, in our present study, the inclusion of Fröhlich interaction addresses limitations in the conventional deformation potential theory formalism, allowing for a more rigorous and accurate assessment of carrier mobility. Interestingly, Sn0.5Pb0.5O reveals superior Seebeck values for both charge types, with 1127.4 μV/K (p-type) and −1078.4 μV/K (n-type) at 300 K, compared to SnO and PbO, attributed to its higher band effective mass and moderate carrier concentration within the system. Moreover, our results reveal that Pb substitution in Sn0.5Pb0.5O benefits n-type transport by increasing carrier concentrations; however, it adversely affects p-type conductivity due to heavier hole effective masses and reduced mobility. Henceforth, leveraged by the superior phononic and electronic transport properties, Sn0.5Pb0.5O composition emerges as a superior n-type thermoelectric material that outperforms the other two systems, as its ZT reaches a significant maximum value of 3.19 at 900 K.