The effect of dielectric heterogeneity on the pyroelectric response of PVDF

Understanding the dynamical response to the applied electric and heat field is crucial in pyroelectric applications of polymers, although their heterogeneity on molecular and crystalline level and the nonuniform distribution of electric charge make it complex. We studied the effect of dielectric heterogeneity induced during electric polarization in uniaxially and biaxially oriented PVDF films. Both pyroelectric and dielectric response of PVDF poled in low dc field and corona-charged was measured over a wide frequency range. We find that heterogeneity on the crystalline level is responsible for the piling up of the field-induced electric charges which causes an increase in the relaxation time ascribed to the relaxation process in the MHz range. It is also concluded that the dielectric heterogeneity in is important only in the case when the front electrode of the pyroelectric sensor is that which was grounded during dc poling