Phonon Scattering by Cottrell Atmospheres Surrounding Dislocations

Cottrell atmospheres modulate the solute concentration of alloys and lead to fluctuations in phonon velocity essentially proportional to the dislocation strain field. Normally one regards point defects as ineffective in scattering phonons at the very low temperatures when the thermal resistance due to dislocations is important. However, the modulation of the impurity concentration about the dislocations increases the phonon scattering by dislocations if heavy impurities are associated with positive dilatation, or light impurities with negative dilatation, and decreases phonon scattering for the opposite combinations. Cottrell atmospheres may thus account for an apparent dependence of phonon scattering by dislocations on the solute content of alloys, as well as changes in the lattice thermal conductivity with aging.