Abstract
Multi-layer ferroelectrets consisting of fluoroethylenepropylene (FEP) copolymer and open-porous expanded polytetrafluoroethylene (ePTFE) films exhibit stable internal electret charges, high piezoelectric coefficients and heat resistance, making them promising candidates for wearable sensors or nanogenerators in body-area networks. Here, three- and five-layer (FEP/ePTFE/FEP and FEP/ePTFE/FEP/ePTFE/FEP) ferroelectret stacks were laminated and poled in a corona discharge. The resulting charge distributions were measured by use of the pulsed electro-acoustic (PEA) method and revealed that charges of opposite polarity were trapped at the interfaces between the FEP and ePTFE layers. Thus, the existence of one macro-dipole in the three-layer structure and of two macro-dipoles in the five-layer structure was directly shown for the first time. Moreover, electric-displacement-versus-electric-field (D-E) loops revealed that remnant polarization is given by the number of macro-dipoles in the respective stack. Due to the addition of the macro-dipoles, the piezoelectric d 33 coefficient of the FEP/ePTFE/FEP/ePTFE/FEP stack reaches 200 pC/N even under a potentially non-uniform compression of the soft ePTFE layers. The results should be useful for a better understanding and a performance optimization of ferroelectrets in self-powered intelligent devices.
Original language | English |
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Article number | 145502 |
Number of pages | 7 |
Journal | Journal of Physics D: Applied Physics |
Volume | 57 |
Issue number | 14 |
DOIs | |
Publication status | Published - 2024 |
Funding
The authors are very grateful to Professor George Rossetti for providing the PM3500 d 33 meter for the piezoelectrical measurement and to BHA Altair, LLC, a Parker Hannifin Company, for providing the expanded PTFE films employed in this study.Keywords
- charge distribution
- charge-spring model
- ePTFE + FEP ferroelectret
- piezoelectricity