Piezoelectric-Property Adjustment of Cellular Ferroelectrets by Foam-Structure and Geometry Variations

Piezoelectric materials are the active elements in e.g. ultrasound transducers and thus widely used in sensor and actuator systems. The rather recent addition to ultrasonic transducer materials are the so-called ferroelectrets, voided piezoelectric-active polymer films. One type among the most studied ferroelectrets is cellular polypropylene. The properties of ferroelectrets, such as low elastic stiffness, high piezoelectric activity, good matching with air makes them suitable as ultrasonic transducer material. Here, we demonstrate the controlled adjustment of the piezoelectric properties, especially of the resonance frequency of cellular polypropylene films by means of transducer-structure modifications.