Naval Device Applications of Relaxor Piezoelectric Single Crystals

"The properties of single crystal piezoelectrics will be exploited for broad bandwidth, high frequency sonar. Crystal sonar investigations based on Tonpilz transducers utilizing the "33" resonance mode have shown limitations on bandwidth due to less thanideal resonator aspect ratio. This is a result of the crystals' low elastic stiffness, which leads to short resonators with large lateral dimensions. To address this issue an alternative design is proposed utilizing the "31" resonance mode with theresonating length oriented along the crystallographic direction. Crystals with this orientation are known to have high properties; and since prestress for such a design would be applied perpendicular to the poling direction, "31" mode Tonpilzelements may exhibit lower loss and higher reliability than "33" mode designs. The feasibility of "31" mode Tonpilz resonators will be determined through property measurements and finite element analysis. For the Phase I Option a prototype single elementTonpilz will be constructed and tested. The targeted application for this work is broadband (>100%), high frequency (45 kHz) synthetic aperture arrays for unmanned underwater vehicles. A feasibility study of crystals for high frequency (>100 kHz) sidelook sonar is also proposed. High frequency sonar is becoming ever more important to the Navy through expanded use of unmanned underwater vehicles (UUV). Proposed missions for many UUV's involve