Ultrasonic and Piezoelectric Investigation of Sn 2 P 2 S 6 Type Photosensitive Ferroelectric-Semiconductor Crystals.

The investigation results of ultrasonic and piezoelectric properties of Sn 2 P 2 (S,Se) 6 , CuInP 2 S 6 and CuCrP 2 S 6 ferroelectric-semiconductors single crystals are presented. In Sn 2 P 2 S 6 type crystals ultrasonic attenuation caused by acoustoelectric interaction after illumination showed fast and long term relaxations. Anomalies of ultrasonic velocity and attenuation at phase transitions have been established in CuInP 2 S 6 and CuCrP 2 S 6 crystals. The piezoelectric detection of longitudinal ultrasonic signal by thin plate of CuCrP 2 S 6 crystal was observed. In the high temperature phase pretransitional effects in ultrasonic and piezoelectric properties were clearly seen. Such effects can be determined by polar clusters, existing above phase transition temperature. [ABSTRACT FROM AUTHOR]