Preexisting polarization and influence of electrode materials on PVF2 electrets as determined by thermal pulse and pyroelectric methods

Abstract

A number of polyvinylidene fluoride (PVF₂) electrets were prepared with different permutations of gold and aluminum electrodes and poled with dc fields up to 160 MV m⁻¹ at room temperature. Polarization distributions were measured by the thermal pulse method and pyroelectric coefficients were determined. Quantitative measurements were made of a significant level of polarization in nominally unpoled PVF₂ and a contact electrification mechanism was proposed. No consistent effects of electrode materials on polarization distribution were found. PVF₂ poled at room temperature has its highest polarization near the center of the thickness in contrast to the results on samples poled at elevated temperatures and cooled inhomogeneously with the field applied.