1.3 - Thermal transport by phonons in thermoelectrics

Abstract

Thermoelectric materials are capable of directly converting heat into electricity by the Seebeck effect, which are applicable to a wide range of industrial applications. For semiconductor thermoelectrics, one of the most effective ways to enhance their performance is to use nanostructures to significantly reduce their lattice thermal conductivity, which is governed by lattice vibrations referred to as phonons, without dramatically sacrificing their electrical properties. Hence, the transport of phonons in nanostructured thermoelectrics is of crucial importance. This chapter stresses the basic concepts and fundamental principles of the transport of phonons in nanostructured materials. Starting with the concepts of phonons and phonon Boltzmann transport equation, we can derive the phonon gas model for thermal conductivity. Various scattering mechanisms of phonons that affect the thermal conductivity in nanostructured materials, well-established theoretical and experimental methods used for the investigation of phonon transport, and examples in terms of manipulating phonons with nanostructures in the field of thermoelectrics are described.