Damping of Dislocations in Lead Single Crystals

Measurements have been made of the attenuation of longitudinal waves along the 〈110〉 direction in a lead single crystal over a frequency range from 30 to 150 Mc/sec and in a temperature range from 60° to 300°K. The attenuation can be divided into a square-law frequency term and a term consistent with the theoretical form of dislocation attenuation at high frequencies. By determining the high-frequency asymptote of the dislocation internal friction and by assuming a reasonable dislocation density, the drag coefficient for the dislocations can be evaluated. The measurements are consistent with the sum of a phonon scattering term and a phonon viscosity term. The square-law attenuation is about twice as large as the thermoelastic loss and over a temperature range is in agreement with the sum of a thermoelastic loss plus a phonon viscosity loss.