PIEZOELECTRIC COMPOSITES WITH HIGH-SENSITIVITY AND HIGH CAPACITANCE FOR USE AT HIGH-PRESSURES

A new type of piezoelectric composite has been developed for oceanographic applications. The composites have a large figure of merit (d(h) . g(h) or d(h) . g(h)/tan-delta), a large dielectric constant (K) and low dielectric loss, as well as great mechanical strength. A shallow cavity between the PZT ceramics and thick metallic electrode is designed to convert a portion of the z-direction stress into a large radial and tangential stress of opposite sign, thereby causing the d33 and d31 contributions to d(h) to add rather than subtract, and raising the figure of merit. Theoretical stress analysis was carried out using an axisymmetric finite element method. Experimental results show that the d(h) g(h), K and withstandable pressure are extremely high.