It has been shown in the present work that the analytical expression of phonon-phonon scattering strength as obtained by Roufosse and Klemens together with an exponential factor can account for most of the observed phonon resistivity of Ge in both the high- and low-temperature regions. For the low-temperature region we have taken the results of Geballe and Hull for both the natural and isotopically enriched samples of Ge. For the high-temperature region we have considered the experimental results of Glassbrenner and Slack. As an additional example of the application of Klemens's expression, we have considered the phonon conductivity results for KCl in both the low- and high-temperature regions. The low-temperature results are taken from Seward's paper and the high-temperature data for KCl are from the measurements made by Devyatkova and Smirnov. For KCl, Klemens's expression, however, overestimates the three-phonon scattering strength by a factor which lies between 10 and 20 in both the low- and high-temperature regions. The form chosen for the phonon-phonon relaxation rate in the present paper has the merit of going smoothly from a correct high-temperature form to a form which approaches (but does not quite equal) the correct low-temperature form.

• Received 17 September 1974

DOI:https://doi.org/10.1103/PhysRevB.15.1219