Phonon conduction in PbSe, PbTe, and PbTe1−xSex from first-principles calculations

Abstract

We apply first-principles calculations to lead selenide (PbSe) and lead telluride (PbTe) and their alloys (PbTe[subscript 1−x]Se[subscript x]), which are potentially good thermoelectric materials, to investigate their phonon transport properties. By accurately reproducing the lattice thermal conductivity, we validate the approaches adopted in this work. We, then, compare and contrast PbSe and PbTe, evaluate the importance of the optical phonons to lattice thermal conductivity, and estimate the impacts of nanostructuring and alloying on further reducing the lattice thermal conductivity. The results indicate that (1) the optical phonons are important not only because they directly comprise over 20% of the lattice thermal conductivity but also because they provide strong scattering channels for acoustic phonons, which is crucial for the low thermal conductivity; (2) nanostructures of less than ~10 nm are needed to reduce the lattice thermal conductivity for pure PbSe and PbTe; and (3) alloying should be a relatively effective way to reduce the lattice thermal conductivity.