Effective polarization fatigue from repeated dielectric barrier discharges in cellular polypropylene ferroelectrets

Abstract

Polarization fatigue is observed when cellular polypropylene (PP) ferroelectrets are subjected to high-voltage cycles. The fatigue rate strongly depends on the amplitude and the number of the applied voltage cycles, whereas the frequency and the waveform of the voltage do not have a strong influence. The much lower piezoelectric activity of significantly fatigued cellular PP ferroelectret films recovers in part after a storage period of typically several hours in ambient air. It is believed that the effective polarization fatigue is mainly caused by the plasma modification of the internal surfaces effected by the repeated dielectric barrier discharges inside the voids.

Fatigue and recovery of cellular-polypropylene piezoelectrets during and after dielectric-barrier discharges

“…It is observed that for severely fatigued samples, the piezoelectricity partially recovers with the storage time after fatiguing [10]. Right after the fatigue process with 1.8×10 5 DBD cycles, a much lower d 33 coefficient of around 15% of the initial value is observed.…”

“…When fatigued samples are stored in the lab for sufficiently long periods, the chargeability of the cavities partially recovers. However, repeated DBDs are detrimental to the stability of the internally trapped charges and hence of the piezoelectricity [10,11].…”

Beneficial and detrimental fatigue effects of dielectric barrier discharges on the piezoelectricity of polypropylene ferroelectrets

“…Our previous study showed that repeated DBDs in air result in significant deterioration of the chargeability of the voids, leading to fatigue in the piezoelectricity in ferroelectrets. 27 In this paper, we present new experimental results to confirm and further illustrate the plasma-polymer interactions during repeated DBDs in the voids as the mechanism of polarization fatigue. We show that the repeated microplasma discharges modify the internal polymer surfaces of cellular ferroelectrets and thus facilitate the charging process, but they also deteriorate the chargeability of the voids, as well as the stability of the piezoelectricity in the cellular polymer, which demonstrates the influence of molecular dynamics and physico-chemical processes.…”

“…Self-healing of the DBD-induced damage over time: Partial recovery of the piezoelectricity Partial recovery of the piezoelectricity in significantly fatigued cellular PP ferroelectrets had already been observed in our previous study and was attributed to the loss of polar low-molecular-weight oxidized material from the internal surfaces of the voids. 27 Figure 1 shows the evolution of the piezoelectric d 33 coefficients as a function of storage time in ambient laboratory conditions for cellular PP films subjected to slight and moderate fatigue. For comparison, the results for one severely fatigued sample are also shown.…”

“…17 However, the fatigue rate of cellular PP ferroelectrets depends mainly on the amplitude and the number of cycles of the driving voltage, and the frequency and the waveform do not have a strong influence. 27 This prompts us to fit the experimental data using an empirical stretched exponential of the form…”