Piezoelectric properties of nonuniform electrets

A simple (double-layer) model of a nonuniform dielectric is presented along with results of effective piezoelectric coefficient measurements for polypropylene-polyurethane structures. The layers were made of polymers with a significantly different mechanical properties (Young´s moduli). The estimated piezocoefficient for the double-layer corona-formed foil electret was on the order of that for PVDF sensors. The present results open new technological possibilities for the penetration of high-sensitivity low-cost piezoelements and extend the family of materials suitable for such sensors