Neutron Scattering Measurements of Temperature-Dependent Phonon Spectra in Thermoelectric Materials PbTe and (Ag,Sb)Te$_{2}$*

The thermoelectric materials PbTe and (Ag,Sb)Te$_{2}$, which both crystallize in the rocksalt structure, have attracted much attention due to their high \textit{zT} values. Prior theoretical and experimental studies have investigated the phonon dispersions of PbTe, and the importance of the electron-phonon and phonon-phonon couplings has been recognized. However, phonons have not been investigated in details in (Ag,Sb)Te$_{2}$. Also, little is known about the phonon linewidths, which directly correlate with the lattice thermal conductivity. In order to better understand the microscopic origins of the lattice thermal conductivity, time-of-flight and triple-axis inelastic neutron scattering measurements were performed as a function of temperature in both compounds. The results of phonon linewidths and their systematic dependence on temperature are presented, providing a direct measurement of the contribution of phonons to the total thermal conductivity.