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 th eir heterogeneity on molecular and crystalline level and the nonunifor m distribution of electric charge make it complex. We studied the effe ct of dielectric heterogeneity induced during electric polarization in uniaxially and biaxially oriented PVDF films. Both, pyroelectric and dielectric response of PVDF poled in low de field and corona-charged w as measured over a wide frequency range. We find that heterogeneity on the crystalline level is responsible for the piling up of the field-i nduced electric charges which causes an increase in the relaxation tim e ascribed to the relaxation process in the MHz range. It is also conc luded that the dielectric heterogeneity in is important only in the ca se when the front electrode of the pyroelectric sensor is that which w as grounded during dc poling.