Piezoelectric properties of electron-irradiated poly (vinylidene fluoride)

Some of the piezoelectric constants of PVDF are strictly stress dependent. This behaviour is assumed to originate in a contribution of the interphase region between crystalline and amorphous phases to the piezoelectric effect in this material. This assumption is supported by the changes in piezoelectricity after irradiation with fast electrons. Such treatment causes crosslinking predominantly in the amorphous regions and, consequently, significant changes in the mobility of molecular electric moments. The piezoelectric constants become smaller upon irradiation, this being caused by a reduced permanent polarization, by increased mechanical stiffness, and by the reduced reorientability of the molecular electric moments in the interphase. One of the nonlinear piezoelectric coefficients changes its sign at a certain irradiation dose.