Engineering the thermal phonon spectrum for thermoelectric energy conversion

Abstract

The efficiency of thermoelec. (TE) devices depends on materials with low thermal cond., among other properties, but thermal phonons are sufficiently poorly understood that achieving this low thermal cond. remains challenging. Recent works have demonstrated that the thermal phonons responsible for heat conduction possess a broad mean free path spectrum, yet this spectrum remains unknown for most materials and is often approximated using av. values. In this talk, I will describe our efforts to directly measure and engineer the thermal phonon spectrum using computation and expt. Exptl., I will describe our efforts to directly measure the phonon mean free path spectrum using a new exptl. technique. Computationally, I will demonstrate the importance of considering the size distribution of nanostructures to achieve the min. thermal cond. in solids.