High power factor and ultra-low lattice thermal conductivity in Sn1−xWxTe alloys via interstitial defects modulation

Abstract

SnTe, a potential substitute for excellent medium-temperature thermoelectric (TE) material PbTe, has recently attracted much attention in TE energy conversion. Herein, we demonstrate a rare and effective strategy to synergistically optimize the electrical and thermal transport properties of SnTe by introducing Tungsten(W) interstitial defects. Concretely, the formation energy of intrinsic Sn vacancy defects is reduced by introducing W-interstitial defects, thus increasing the hole carrier concentration and overall electrical conductivity. Meanwhile, the increase of band degeneracy (band flattening and valence band convergence) markedly enhances the Seebeck coefficient, which exhibits the high average power factor of ∼17.79 μWcm−1K−2. Moreover, the lattice thermal conductivity is significantly reduced to 0.46 Wm−1K−1, which arises from the enhancement of phonon scattering caused by various processes including dislocations, crystal defects and multiscale nanoprecipitation. These combined effects lead to a maximum ZT value of ∼0.79 at 823 K for Sn0.97W0.03Te, especially the average ZT value remarkably increased to 0.26. Conclusively, unlike conventional work to optimize electrical transport performance (reducing hole carrier concentration), this work provides an innovative strategy to significantly improve the electrical properties of SnTe through the modulation of W-interstitial defects.