Mechanism of the influence of ultrasonic and electric fields on the vibrational motion of dislocations in the ultrasonic vibration of alkali-halide crystals

Abstract

The influence of electric and ultrasonic fields on the vibrational motion of disolocations in alkali-halide crystals was investigated by the method of current-voltage characteristics I(V) and the measurement of the amplitude dependence of the damping Q⁻¹(ε₀) and the defect of the modulus ΔM/M(ε₀) in a composite piezoelectric oscillator. An abrupt decrease of I(t) is observed at amplitudes of the relative deformation ε₀=10⁻⁶−10⁻⁵. The internal friction at the same ε₀ reveals an amplitude dependence, while establishment of steady values is attained by passage through the maximum of Q⁻¹(t). The electric field shifts the amplitude of the onset of the abrupt decrease of I(t) into the region of smaller ε₀. The displacement of the vibrating dislocation at an amplitude ε₀ corresponding to the onset of the singularity of I(t) is near the value of the radius of the Debye-Hückel cloud surrounding it. The characteristic times of the process correspond to the relaxation time of a free charge in an insulator.