Ferroelectric ceramics and composites for piezoelectric transducer applications

A concise overview of ferroelectric ceramics and composites, which constitute the backbone of transducer applications such as actuators, sensors, energy harvesting, and storage are provided. For piezoelectric composites based on ferroelectric ceramics, underlying principles are developed using linear equations of state for piezoelectricity and the concepts of crystalline anisotropy, symmetry, composite connectivity, and form factor engineering as unifying themes. Emphasis is given to diphasic piezoelectric composites which have revolutionized transducer engineering in fields such as sonar and medical ultrasound imaging. It is shown that through judicious selection of a ferroelectric ceramic in conjunction with an inactive material such as a polymer or metal, effective material properties exceeding the performance of single-phase ceramics can be achieved. The application of traditional composite strategies and advances in fabrication technologies to rapidly growing fields such as dielectric energy storage and piezoelectric energy harvesting are also discussed.