Three-layer piezoelectrets from fluorinated ethylene-propylene (FEP) copolymer films (original) (raw)
Related papers
Journal of Applied Physics, 2018
In ferroelectrets, the piezoelectricity stems from the charges of both polarities trapped on the inner surfaces of the cavities in the material, so that its thermal stability is defined by the stability of the respective charges. In the present work, a template-based lamination technique has been employed to fabricate tubular-channel ferroelectrets from fluoroethylenepropylene (FEP) films. It has been shown that the piezoelectricity in FEP ferroelectrets decays at relatively low temperatures due to the inherently lower thermal stability of the positive charge. In order to improve charge trapping, we have treated both FEP films and inner surfaces of the ferroelectret cavities with titanium-tetrachloride vapor, using the atomic-layer-deposition technique. Using surface-potential-decay measurements on FEP films, we have found that the charge-decay curves shift by more than 100 C to the higher temperatures as a result of the surface treatment. Direct measurements of piezoelectric d 33 coefficients as a function of temperature have shown that the piezoelectric stability is likewise improved with the d 33-decay curves shifted by 60 C to the right. The improvement of electret/ ferroelectret properties can be attributed to the formation of the deeper traps on the chemically modified FEP surface. SEM micrographs and EDS analysis reveal island-like structures with titanium-and oxygen-containing species that can be responsible for the deeper trapping of the electret charges.
Journal of Applied Physics, 2009
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.
Mini‐review: The Promise of Piezoelectric Polymers
2018
Recent advances provide new opportunities in the field of polymer piezoelectric materials. Piezoelectric materials provide unique insights to the fundamental understanding of the solid state. In addition, piezoelectric materials have a wide range of applications, representing billions of dollars of commercial applications. However, inorganic piezoelectric materials have limitations that polymer ferroelectric materials can overcome, if certain challenges can be addressed. This mini-review is a practical summary of the current research and future directions in the investigation and application of piezoelectric materials with an emphasis on polymeric piezoelectric materials. We will assume that the reader is well versed in the subject of polymers, however, not as familiar with piezoelectric materials
The promise of piezoelectric polymers
Polymer International, 2018
Recent advances provide new opportunities in the field of polymer piezoelectric materials. Piezoelectric materials provide unique insights to the fundamental understanding of the solid state. In addition, piezoelectric materials have a wide range of applications, representing billions of dollars of commercial applications. However, inorganic piezoelectric materials have limitations that polymer ferroelectric materials can overcome, if certain challenges can be addressed. This mini‐review is a practical summary of the current research and future directions in the investigation and application of piezoelectric materials with an emphasis on polymeric piezoelectric materials. We will assume that the reader is well versed in the subject of polymers, but not as familiar with piezoelectric materials. © 2018 Society of Chemical Industry
Sensors and Actuators A-physical, 2016
Ferroelectrets are a recent addition to the family of piezoelectric polymers. Ferroelectrets are spacecharge electrets with a heterogeneous and usually cellular foam structure. They are flexible, available in large areas and show strong piezoelectric response. Due to their low acoustic impedance they have strong application potential in airborne ultrasonic transducers. Here, the influence of temperature on the electromechanical and ultrasonic properties of polypropylene (PP) ferroelectrets was addressed. PP ferroelectrets were subjected to repeated temperature variations. The characterization was performed by means of dielectric resonance spectroscopy (DRS) and Laser-Doppler Vibrometry (LDV). Profound variations in the piezoelectric properties during thermal cycling were observed and correlated to the changes in the elastic properties. Exposure to elevated temperatures resulted in a reduction in the piezoelectric response and an increase in the elastic stiffness constant which also shifted the thickness-extension resonance peaks towards higher values. Large differences in piezoelectric properties were discovered between the first and the subsequent cycles. To decrease the influence of temperature cycling on the piezoelectric properties of PP ferroelectrets, annealing was used to advantage. Annealing treatments with different durations and different annealing temperatures were investigated. A particular procedure yielding foam stiffening and a sufficiently high piezoelectric activity was determined and was employed for further investigations. The piezoelectric properties of the annealed ferroelectrets varied much less when compared to non-annealed ferroelectrets. Characterization of thermally cycled annealed and non-annealed films revealed relatively homogeneous phase and amplitude distributions of the surface-vibration below the resonance, which resembles a piston-like response. Piston-like response was not significantly deteriorated by thermal cycling below the resonance frequency. This was corroborated for all samples by measuring the acoustic directivity of them in the farfield, at frequencies below the resonance. At the resonance, much higher distortions of the response were observed as revealed from the phase images.
Advances in the study of piezoelectric polymers
Russian Chemical Reviews, 2019
The literature review based on the works published over the last decade concerns the progress in research on innovative piezoelectric materials with current or potential practical applications. At the beginning, the nature of piezoelectric phenomenon is clarified. The main emphasis is put on presentation of polymers, biopolymers and polymer composites as well as hybrid materials with piezoelectric properties. Moreover, carbon nanomaterials are also included. These materials have recently become an intensively developing field, as evidenced by numerous scientific publications. Furthermore, the recently reported main methods of characterizations and selected examples of modern applications of piezoelectric materials in various fields (electronics, industry, medicine) have been discussed. The bibliography includes 217 references.
Nanostructured piezoelectric polymers
Journal of Applied Polymer Science, 2014
Among the wide variety of piezoelectric materials available, polymers offer an interesting solution because of their high mechanical flexibility, easy processing, and conformable features; they maintain good ferroelectric and piezoelectric properties. The most prominent examples of these are poly(vinylidene fluoride) (PVDF) and its copolymer, poly(vinylidene difluoride-trifluoroethylene) [P(VDF-TrFE)]. An attractive prospective consists of the preparation of nanostructured polymers. It has been shown that the dimensional confinement of such macromolecules down to the nanoscale can improve their piezoelectric properties because the tailoring of the chemical structure is performed at the molecular level. In this review, we show how nanostructured polymers can be obtained and discuss reports on the ferroelectric and piezoelectric properties of nanostructured PVDF and P(VDF-TrFE) materials. In particular, we show how dimensional confinement leads to piezoelectric nanostructures with relevant performances, with a focus on the macromolecular structural arrangement that enhances their behavior. Experimental results and applications are also reported to compare the performances of different nanostructuration processes and the polymer efficiencies as piezoelectric materials.
Journal of Applied Polymer Science, 2004
Piezoelectricity of ferroelectric thin polymer films strongly depends on the poling condition. We can classify them as conventional electrical and novel nonelectrical poling. These experiments show the comparative results on piezoelectricity induced from various poling processes (i.e., electrical corona poling, nonelectrical surfaceenergy poling, and a combination of both methods simultaneously in various poling conditions). The most interesting result confirmed that the piezoelectricity increased significantly when the combination poling was applied with appropriate metal substrate and temperature decreasing rate.
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2005
Piezoelectric cellular polypropylene films, socalled ferroelectrets, are assembled in a stack with two active transducer layers. The stack is characterized with respect to its linear and quadratic response in a frequency range from 1 kHz to 80 kHz. A relatively smooth frequency response in the sound-pressure level is found for the individual layers as well as for both layers driven in phase. The piezoelectric response of the two-layer stack is twice the response of an individual layer over a rather broad frequency range. Furthermore, the influence of the preparation conditions on the resonance frequency and the effect of the quadratic distortion on the radiated sound are investigated both for the individual transducer films in the stack and for the stack system as a whole. Michael Wegener was born on September 24, 1968, in Neuruppin, Germany. He studied physics and mathematics at the University of Potsdam, Potsdam, Germany, from 1990 to 1995. In February 2000, he received a Ph.D. degree in physics. Major topics of his Ph.D. work were the electrical properties of polymers (mainly pyro-, piezo-, and ferroelectricity) and their variation during and after electrical, thermal, and chemical parameter changes.