Functional characterization of piezocrystals monitored under high power driving conditions

Relaxor-based ferroelectric single crystals such as PMN-PT are known to exhibit high piezoelectric properties compared with conventional piezoelectric ceramic materials, such as PZT-8. With advances in piezoelectric material development, including compositional engineering, single crystals with higher rhombohedral-to-tetragonal phase transition temperature (T_RT), higher coercive field (E_C) and higher mechanical quality factor (Q_M) have emerged, the principal example being Mn:PIN-PMN-PT. The improvements have opened up a wider application range, including more demanding high power applications where the performance of conventional materials may deteriorate at elevated temperatures resulting from intrinsic loss mechanisms. Characterization of these piezocrystals under practical and active conditions is therefore important, improving understanding of material behavior and facilitating transducer design in finite element analysis for demanding applications. In this paper, we report an active piezoelectric material characterization system that allows high resolution impedance spectroscopy under conditions similar to those experienced by piezoelectric materials in high power ultrasonic applications. The temperature consequent on the drive voltage is adaptively stabilized using a control algorithm. System function has been verified by testing with a Mn:PIN-PMN-PT thicknessextensional plate and functional characterization has been conducted on Generation I, II and III piezocrystals, with detailed analyses and comparisons of performance stability and material property variation with temperature.