Robert Y. Ting
U.S. Naval Res. Lab., Underwater Sound Reference Detachment, P. O. Box 568337, Orlando, FL 32856-8337
New emphasis on active sonar applications requires the development of compact, high-power sonar projectors. For low-frequency use, one desires to be able to drive the transducer elements at high electric field levels in order to achieve large strains. The conventional lead--zirconate--titanate (PZT) ceramics have been widely used for the design and fabrication of sonar projectors, but these ceramics suffer the shortcomings of strain limitation and nonlinear properties under high drive. In recent years, the Navy has been developing new electrostrictive ceramics of the lead--magnesium--niobate family, because these electrostrictive ceramics can produce much greater strains than the PZTs. In particular, a new class of lead--magnesium--niobate lead--titanate (commonly called PMN--PT) solid solution compositions has been found to offer the combined advantages of high-strain, low-dielectric, and hysteresis losses. The development of these materials is summarized, and the test results from prototype transducers fabricated using the new electrostrictive PMN--PTs are also presented. [Work supported by ONR/T.]