Thermally stable dynamic piezoelectricity in sandwich films of porous and nonporous amorphous fluoropolymer

Porous amorphous fluoropolymer films of very low stiffness were produced by a solvent evaporation technique. Corona-charged sandwich films consisting of a porous and a nonporous layer exhibit piezoelectric thickness-extension resonances in their dielectric spectrum, through which the temperature dep endence of their dynamic stiffness, coupling factor, and piezoelectric coef ficient could be determined. Their strong piezoelectricity with coefficient s of up to 600 pC/N at temperatures of at least 120 degreesC could make the se polymer electret films interesting candidates for sensor and actuator ap plications in elevated temperature environments. (C) 2001 American Institut e of Physics.