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 k_t equal to 0.57. As a value of k_t 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 ${\mathrm{(\epsilon }}_{33}^S{\mathrm{/\epsilon }}_0\text{= 30)}$ , 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.