Peculiarities of dislocation generation by block boundaries in alkali halide crystals during ultrasonic vibrations

The generation of dislocations by block boundaries in alkali-halide crystals under the action of ultrasound was investigated making use of a computer defet modeling method. Ultrasonic vibrations were excited in a double piezoelectric oscillator at the frequencies 60 and 73 kHz. Specimens of KCl and KBr with =0° and =30°, where is the angle between the fourfold axis and the propagation direction of the ultrasound, were investigated. The change in the dislocation structure was determined from the volt-ampere characteristics. It was established that the dislocation sources located near the block boundaries started to operate at stress values one third of those at which other sources operated. Modeling showed that the existence of boundaries had a significant effect on the operation of small-size sources. The experimental estimate of the reduction of the critical stress exceeds the theoretical one.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 52–55, March, 1984.