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

The authors report local domain-inversion phenomena in LiNbO/sub 3/ and LiTaO/sub 3/ plates and discuss applications of antipolarity domains to various piezoelectric devices. Ferroelectric local domain inversion takes place in LiNbO/sub 3/ during the Ti diffusion process at around 1000 degrees 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.<
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