ICT2014 Abstracts

     Significant effort has been expended to reduce the lattice thermal conductivity (k) of thermoelectric materials through mechanisms such as alloying and nanostructuring.  Here, we discuss how tailoring point defect scattering may provide another way to achieve lower k and better thermoelectric performance in materials with a large mass difference between the constituent atoms (e.g., PbS and Mg₂Sn).  We employ a rigorous first principles thermal transport approach which combines full solution of the Peierls-Boltzmann transport equation with interatomic forces determined from density functional theory.  This atomistic approach has demonstrated good agreement with measured k data for a number of systems without use of adjustable parameters.   

     We examine the role of different point defect scattering mechanisms in determining k of a variety of systems, including promising thermoelectric materials Pb(S/Se/Te), Mg₂(Si/Sn) and alloys.  We show that phonon scattering from point defects such as isotopic mass differences, vacancies and substitutional atoms are enhanced in large mass difference materials due to the increased motion of the heavy atoms.    We examine the interplay of phonon-point-defect scattering and phonon-phonon scattering in systems with intrinsically low k, and we quantify the reduction of k with point defect scattering in thermoelectric materials with strain, alloying and nanostructuring.  Further, we compare and contrast k results for which point defect scattering is calculated within the Born approximation versus a Green’s function method.