Template-based fluoroethylenepropylene piezoelectrets with tubular channels for transducer applications

Abstract

Polarization switching at the nanoscale in ferroelectric copolymer thin films Appl. Phys. Lett. 99, 142904 (2011) Tunable temperature dependence of electrocaloric effect in ferroelectric relaxor poly(vinylidene fluoridetrifluoroethylene-chlorofluoroethylene terpolymer Appl. Phys. Lett. 99, 052907 (2011) Beneficial and detrimental fatigue effects of dielectric barrier discharges on the piezoelectricity of polypropylene ferroelectrets J. Appl. Phys. 110, 024108 (2011) Energy harvesting by nonlinear capacitance variation for a relaxor ferroelectric poly(vinylidene fluoridetrifluoroethylene-chlorofluoroethylene) terpolymer Appl. Phys. Lett. 98, 222901 (2011) Photocrosslinking of ferroelectric polymers and its application in three-dimensional memory arrays Appl. Phys. Lett. 98, 183302 (2011) Additional information on J. Appl. Phys. We describe the concept, the fabrication, and the most relevant properties of a piezoelectric-polymer system: Two fluoroethylenepropylene ͑FEP͒ films with good electret properties are laminated around a specifically designed and prepared polytetrafluoroethylene ͑PTFE͒ template at 300°C. After removing the PTFE template, a two-layer FEP film with open tubular channels is obtained. For electric charging, the two-layer FEP system is subjected to a high electric field. The resulting dielectric barrier discharges inside the tubular channels yield a ferroelectret with high piezoelectricity. d 33 coefficients of up to 160 pC/N have already been achieved on the ferroelectret films. After charging at suitable elevated temperatures, the piezoelectricity is stable at temperatures of at least 130°C. Advantages of the transducer films include ease of fabrication at laboratory or industrial scales, a wide range of possible geometrical and processing parameters, straightforward control of the uniformity of the polymer system, flexibility, and versatility of the soft ferroelectrets, and a large potential for device applications e.g., in the areas of biomedicine, communications, production engineering, sensor systems, environmental monitoring, etc.

Fluoroethylenepropylene ferroelectrets with patterned microstructure and high, thermally stable piezoelectricity

“…Since the thermal stability of d 33 in ferroelectrets is dependent on the retention of the internal space charges, two approaches are possible to achieve this goal. One is the development of new ferroelectrets based on thermally stable electret materials, such as cross-linked PP (XPP) [10], cycloolefines (COC) [11], polyethyleneterephthalate (PET) [12], polyethylene-naphthalate (PEN) [13], and fluorocarbon polymers [14][15][16][17][18][19][20][21][22][23][24][25]; the other is chemical modification, such as surface modification of cellular PP by using fluorination [26]. Of these two approaches, the former one, in particular the one using fluorocarbon films, has shown the most promise.…”

Fluoropolymer piezoelectrets with tubular channels: resonance behavior controlled by channel geometry

“…With the availability of the thermo-forming techniques and the resulting rather uniform void geometries, new processes were recently developed for also controlling the geometrical parameters of the voids in the multi-layer systems [19,20]. Here, one of these techniques, i.e.…”

Piezoelectric performance of fluor polymer sandwiches with different void structures

“…If devices based on piezoelectrets are to work at elevated temperatures, then thermally stable piezoelectrets are required. Therefore, with increased understanding of piezoelectrets, most of which relates to commercially available polypropylene (PP) piezoelectrets having relatively low thermal stability, thermally stable piezoelectrets have been actively developed either by fabricating films based on thermally stable materials [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] or modifying existing PP films [21,22].…”