THE DISLOCATION UNPINNING FROM STOPPERS IN KBr SINGLE CRYSTALS СAUSED BY ELASTIC STRESSES AND TEMPERATURE

Abstract

The impulse echo-method was applied to study, in the temperature range 300…435 K and at 7.5 MHz frequen-cy, the dislocation attenuation αd(σ) in KBr crystals as a function of static loading in the quasi-elastic strain range. It has been found that the temperature increase at stresses σ > σy (σy is the yield limit of a crystal) leads to the inten-sive dislocations’ unpinning. Consequently, concentration of stoppers, controlling their motion, sharply decreases and the effective length of oscillating dislocation segments increases. As a result of experimental data processing the energy of the impurity atom binding with dislocation U0 was calculated in the following work.