Importance of the metal–polymer interface for the piezoelectricity of polyvinylidene fluoride

Abstract

The piezoelectric effect in films of polyvinylidene fluoride (PVF2) is investigated using optical and ultrasonic detection techniques. From the analysis of the vibrational resonance frequencies of a freely suspended film we conclude that the polarization induced in PVF2 is inhomogeneous across the volume of the sample. Poling the foils in a sandwich configuration or using blocking electrodes, we can clearly demonstrate that the piezoelectric effect in PVF2 originates from the positive metal electrode. Monitoring the time dependence of the piezoelectric effect during the poling process, a fast and slow component are observed. Using a blocking electrode, however, the same dynamical poling behavior is found only if the contacting metal electrode is positive. In view of these observations, which clearly demonstrate the importance of the metal–polymer interface for the strong piezoelectricity of PVF2, the existing theoretical models, based on the bulk properties of the polymer, are critically reviewed.

Observation of charge compensated polarization zones in polyvinylidenefluoride (PVDF) by piezoelectrically generated pressure step wave (PPS) response

“…1, a piezoelectric active layer at the positive poling electrode in agreement with the results of other authors [3], [4] for thermally poled films; whereas in films poled by corona discharge, see Fig. 2, an internal piezoelectric active zone without signal contributions at the film boundaries has been found.…”

Polarization of block textured films of ferroelectric copolymers of vinylidene fluoride with tetrafluoroethylene in an external field

“…If we assume that the pyro and piezocoefficients are proportional to the value of P r [1][2][3], the response to the heat impulse and the pressure wave of polarized film, in accordance with our data, should be higher on the anode side than on the cathode side. Indeed, this phe nomenon was observed in [42,43]. As mentioned above, the effect of the number of polarization cycles on change in the parameters of the current-voltage characteristics (Fig.…”

Charge distribution and transport in polymers

“…Charge injection and charge-dipole interaction have long been considered important factors for the generation and stabilization of the permanent polarization in PVDF and in its copolymers [5,96]. During the last decade, the evidence in favor of a model based on the key role of injected charges has been strengthened by a number of significant experiments by Eisenmenger and his coworkers [97-1061. supported by studies in some other laboratories .…”