Investigation of Ultrasonic and Acoustoelectric Properties of Ferroelectric-Semiconductor Crystals

The ultrasonic velocity and attenuation anomalies were observed near phase transitions (PT) in CuInP₂(S,Se)₆ semiconductor crystals, where S was partially substituted by Se. It was shown that, crystals became piezoelectric not only in low temperatures below PT in ferroelectric phase but also at room temperature, which is far above the phase transition and under DC bias electric field, the electrostriction induced piezoelectricity appears. The anomalies of ultrasonic velocity, attenuation, second harmonic, and acoustoelectric voltage were also observed near the phase transitions in Cu ₆ PS ₅ I single crystals. These crystals belong to the polar symmetry group 3m at room temperature and exhibit a ferroelastic phase transition at 270 K.

Keywords:

• Ferroelectric-semiconductor
• phase transition
• ultrasonic properties
• acoustoelectric effect

Acknowledgments

Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005;