BEHAVIOR OF PIEZOELECTRIC CERAMICS UNDER VARIOUS ENVIRONMENTAL AND OPERATION CONDITIONS OF RADIATING SONAR TRANSDUCERS

Design of transducers for lower frequency, high power density, and deeper submersion puts increasing demands on piezoelectric transducer materials. It has been demonstrated that appropriate lead titanate zirconate ceramics can operate under high bias stress and at high power levels without failure. However, changes in physical properties, especially in permittivity as a result of a change in static compressive stress and changes in permittivity and tan delta with drive amplitude, have become increasingly of concern. The mechanisms whereby the nonlinear characteristics of ferroelectric ceramics bring about dependence of physical properties on electric and mechanical stress are discussed. The basic differences in behavior under high electric and mechanical stress of alkaline earth-substituted lead titanate zirconate ('hard') and donor- doped lead titanate zirconate ('soft') are outlined. Data are given also for a new 'very hard' lead titanate zirconate, PZT-8. Stabilizing treatments which tend to minimize pressure effects are described. Emphasis on behavior under environmental and operating conditions is placed on the following: (1) Variations in the piezoelectric constant d sub 33 and permittivity with static compressive stress parallel to the polar axis. (2) Changes of permittivity with time under maintained stress. (3) Changes of permittivity and tan delta with electric field at various levels of compressive stress parallel to the polar axis. (4) Variations in permittivity and d sub 33 with stress cycling (stress parallel to the polar axis). Presented at Navy Seminar on Piezoelectric Ceramics, 24-25 Sep 1964, Washington, DC.