Ferroelectric imprint and polarization in the amorphous phase in P(VDF-TrFE)

Abstract

Poly(vinylidene fluoride-trifluoroethylene) is a ferroelectric copolymer. It is considered a promising candidate for sensors, nonvolatile memory applications, and energy harvesting. However, imprint, a phenomenon associated with ferroelectric polarization, changes reversibly the material properties over time. In particular, imprint results in an increase of the ferroelectric polarization switching time and the coercive field, as well as in the decay of the remanent polarization and the permittivity. We present a concept to explain imprint and present experimental evidence supporting this concept. In this concept, an internal electric field arises as a consequence of the interaction between ferroelectric dipoles and relaxational dipoles present in the crystalline and the amorphous phase, respectively. We use an extended Weiss mean field approach and show that this internal field results in the experimentally observed imprint. In addition, we show that the imprint can be largely suppressed by increasing the copolymer's crystallinity.