Broadband ultrasonic transducers using a using a LiNbO{sub}3 plate with a ferroelectric inversion layer

摘要

We have found a domain inversion phenomenon induced by simple heat treatment of LiNbO{sub}3. In such a piezoelectric plate with an inversion layer, even-order thickness-extensional modes as well as odd-order modes can be excited piezoelectrically. Therefore, the ultrasonic transducer using such a piezoelectric plate is expected to operate in a wide frequency range. In this paper it is shown that broadband ultrasonic transducers can be obtained at certain thickness ratios of inversion layer to plate and that the transducer characteristics differ depending on whether the inversion layer is on the front side or on the backside. The broadband characteristics are experimentally demonstrated by fabricating transducers with 9MHz or 75MHz center frequency using a 36° rotated Y-cut LiNbO{sub}3 plate with a ferroelectric inversion layer.