Local domain inversion in ferroelectric crystals and its application to piezoelectric devices

The authors report local domain-inversion phenomena in LiNbO₃ and LiTaO₃ plates and discuss applications of antipolarity domains to various piezoelectric devices. Ferroelectric local domain inversion takes place in LiNbO₃ during the Ti diffusion process at around 1000°C, depending on the conditions. Similar domain inversion is caused by proton exchange followed by heat treatment, or even by heat treatment alone at higher temperatures. These domain-inversion phenomena can be caused in local region of plates without applying electric fields. The resulting domains have a reversed polar crystal axis and therefore have various constants opposite in sign to those in the original crystal. Applications described include bending vibrators and hysteresis-tree actuators, VHF and UHF ultrasonic transducers, and surface acoustic wave (SAW) devices