PIEZOELECTRIC PROPERTIES OF Ba2 NaNb5 O15

Abstract
Single‐crystal Ba2NaNb5O15 (z plate) has been found to have a piezoelectric coupling factor in the thickness longitudinal mode kt equal to 0.57. As a value of kt determined by direct measurement, this result is the highest value yet reported for a single‐crystal ferroelectric material usable at and above room temperature. Since this material has good mechanical handling characteristics, a relatively low dielectric constant 33S0 = 30) , and a pure mode of vibration, plates of this material are attractive for applications as high‐frequency longitudinal mode transducers. The approximate values of the thickness shear mode coupling factors for x and y plates are k15 = 0.20 and k24 = 0.20.