Axial compressive stress for depolarization suppression and source level enhancement of underwater projectors made of [011]-poled PZN-PT single crystals

Lead-based relaxor-PT single crystals of rhombohedral phase, such as Pb(Zn1/3Nb2/3)O3-PbTiO3 and Pb(Mg1/3Nb2/3)O3-PbTiO3, exhibit excellent piezoelectric properties and are candidate active materials for high-performance underwater projectors. However, their low coercive field would cause depolarization under high ac drive field, making them unsuitable for high power applications. The present work investigates the effect of axial compressive stress on the depolarization and phase transition behaviors of [011]-poled 32-mode PZN-5.5%PT single crystals. Our results show that with appropriate compressive stress in the [100]-crystal direction, the magnitude of depolarization field of the crystal can be increased to close to the R-O phase transformation field, enabling the application of higher ac drive field. The result further shows that with optimal axial compressive stress, >5 dB increase in the figure-of-merit (FOM) can be achieved without dc bias. The effect of axial compressive stress on material properties of [011]-poled 32-mode PZN-5.5%PT single crystals are also presented, which are useful for underwater projector design purposes.