Modern electrets

Ferroelectrets are cellular dielectric materials with an internal bipolar electret charge that exhibit ferroelectric-like hysteresis and switching behavior. Ferroelectrets have found considerable interest for transducer applications, since they mimic piezoelectricity by their unusual electromechanical properties. They offer very high d/sub 33/ transducer coefficients, comparable with ferroelectric ceramics and typically 20 times larger than that of ferroelectric polymers like PVDF. Ferroelectrets therefore offer a huge potential for the development of large area sensors, as well as for acoustical, ultrasonics, biomedical, underwater and nondestructive testing applications.