Ultrasonic transducers using piezoelectric single crystal perovskites

Solid solutions of the relaxor-based Pb(Zn_1/3Nb_2/3 )O₃ (PZN) and Pb(Mg_1/3Nb_2/3)O₃ (PMN) systems with PbTiO₃ (PT) have been grown in single crystal form. The piezoelectric and dielectric properties of several compositions are reported along various crystallographic directions. The piezoelectric transducer model developed by Kimholtz, Leedom and Matthaei (KLM) was employed to study the behavior of these materials as ultrasonic resonators. Extremely high piezoelectric coupling coefficients (k₃₃ >94%) and a range of dielectric constants (3000-5000) have been observed in these systems on the rhombohedral side of the morphotropic phase boundary (MPB). Relatively low dielectric constants (~1000) and high thickness mode coupling (kt>63%) were observed as typical of tetragonal formulations. The ability to tailor the dielectric and piezoelectric constants with composition and crystal orientation allows the design of very large bandwidth ultrasonic transducers for applications ranging from medical diagnostic imaging to high frequency single element ultrasound backscatter microscopy