Acousto-optic study of nonlinear acoustic properties of layered materials

The investigation of acoustic properties in layered crystals KY(MOo(4))(2) and Si20Te80 isotropic alloy with nanocrystallite inclusions has been carri ed out. The acousto-optic and pulse-echo techniques were used. The measurem ents of ultrasound velocity and attenuation, and also sound wave spectrum e volution along different crystallographic axes in wide ranges of frequency (14-1800 MHz) temperatures (90-300 K) and sound intensities (0.04-100 W cm( -2)) were fulfilled. Extremely large values of nonlinear coefficients and a nharmonicity constants of longitudinal photon modes across the layers and c rystallite boundaries have been found. It has been shown that anharmonicity of the bonding force across the layers determines the anisotropy of the me chanical strength in layered crystals.