Transduction modality near instability in domain engineered relaxor ferroelectric single crystals

A transduction modality based on inter-ferroelectric (FE) transitions in domain engineered single crystals, poised near an instability via mechanical clamping is reviewed. The phase transition is associated with strain levels that are much higher than what could be achieved using the linear piezoelectric mode. They are also accessible at significantly lower drive fields compared to the free state. The large FE-FE polarization change accompanying the phase switching has been utilized to demonstrate the vast electromechanical and thermal energy conversion capabilities of this sensing modality. The harvested mechanical energy density per cycle is nearly two orders of magnitude larger than that of linear piezoelectric bimorphs operating in a resonance-mode. Additionally, being a non-resonant modality, the problems associated with matching the harvester's frequency to that of the structure (for maximum output) are obviated. Magnetoelectric energy harvesters and sensors have demonstrated similarly large coefficients. Compact broadband sound projectors fabricated using this modality have delivered 10-15 dB more source level over two and half octaves compared to the linear piezoelectric mode counterpart. Ongoing research in utilizing this modality in electro-optic modulation is discussed. Advances that have occurred over the last decade in fundamental understanding of this transduction modality and device physics are presented. It is our intent that this up-to-date review will stimulate interest in the applied physics community to further explore the benefits of this transduction modality. This review also summarizes fundamental knowledge gained of relevant issues. The focus of this review is on single crystals and thus the recent work on lead free ceramics is not addressed.