Acoustic emission from ferroelectric crystals

As the spontaneous polaristion in a ferroelectric is reversed by an applied electric field, short duration ultrasonic signals are produced which degrade into the geometric normal vibrational resonance modes of the crystal. Simultaneous visual observation and monitoring of the ultrasonic signals show that these acoustic emissions produced as Pb5Ge3O11 and Gd2 (MoO4)3 are taken round the hystresis loop result from domain wall nucleation and collapse.