The electric behavior of PVDF and P(VDF-TrFE) during corona poling

Preliminary results of measurements made with β-PVDF (uniaxially and biaxially drawn samples), α-PVDF, and P(VDF-TrFE) (60/40 e 70/30 mol.%) are presented, and a procedure for estimating their polarization and the coercive field is described. It is demonstrated that the corona triode with constant current allows one to study the properties of ferroelectric polymeric films under corona poling. It is found that the poling curves of β-PVDF and P(VDF-TrFE) can be reasonably fitted by a model which considers a transport of an excess of free charge, a polarization dynamics given by dP/dt=(P_s-P)/τ (τ∝E^-n, where E is the electric field), and assuming a field-dependent dielectric constant. This model gives a polarization distribution uniform in the region near the back electrode and zero at the sample surface