Piezoelectricity of porous polytetrafluoroethylene single- and multiple-film electrets containing high charge densities of both polarities

Künstler, W.; Xia, Zhang; Weinhold, Till J.; Pucher, A.; Gerhard, Reimund

doi:10.1007/s003390050002

Cited by 78 publications

(26 citation statements)

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“…In such systems quasi-static piezoelectriclike coefficients up to 600 pC/N have been obtained in a composite consisting of hard and soft fluoropolymer films. [32,33] The pyroelectric coefficient of cellular materials is of opposite sign to those of ferroelectric polymers and other ferroelectric materials. [20] An increase of the temperature enhances the sample thickness due to thermal expansion, and thus also increases the macroscopic dipole moments of the voids and the charges on the electrodes, which gives a positive pyroelectric coefficient p 3 .…”

Section: Piezo-and Pyroelectricity Of Internally Charged Cellular Polmentioning

confidence: 98%

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

2005

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Cellular polymers can be internally charged by "microstorms" (silent or partial discharges) within the voids of the polymer foam. The resulting material, which carries positive and negative charges on the internal void surfaces, is called a ferroelectret. Ferroelectrets behave like typical ferroelectrics, hence they provide a novel class of ferroic materials. The soft foams are strongly piezoelectric and can be used, in a wide range of applications, as transducers for interconverting mechanical and electrical signals. Herein, an overview is provided on the preparation of cellular polymers by physical foaming (extrusion, biaxial stretching, and controlled inflation by pressure treatments), on their charging by "microstorms", on their piezo- and pyroelectricity, and on analogies to ferroelectrics. Finally, a survey of selected applications is presented.

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Section: Piezo-and Pyroelectricity Of Internally Charged Cellular Polmentioning

confidence: 98%

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

2005

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“…For example, KACPRZYK elaborated on a two-layer system of corona charged PP and PU films (77) , and GERHARD-MULTHAUPT et al investigated stacks of corona charged porous and non-porous PTFE (78) and reported piezoelectric d 33 coefficient of up to 35pC/N. Even higher values of up to 150pC/N were obtained by KUNSTLER et al with single la yers of porous PTFE carrying a bipolar space charge (79) . However, most significant new class of cellular space charge electrets is based on a concept reported by KIRJAVAINEN (80) .…”

Section: Piezoelectric Applicationsmentioning

confidence: 91%

“…In addition, several other polymers have been shown to have potentially useful piezoelectric properties, such as polyamides (45) , copolymers of vinylidene cyanide (VDCN) (46) , polyureas (47) and polyurethane (PU) (48) mainly due to their lightweight and flexibility. The two layer approach has been investigated with the polypropylene (PP) and PU foams (49) , whilst further research has been investigated on stacks of corona-charged porous and non-porous PTFE (50) and reported piezoelectric d 33 coefficient values of up to 35pC/N and as high as 150pC/N has been obtained with single layer of porous PTFE (51) . Cellular PP foams are usually produced in a modified blow extrusion process (52,53) .…”

Section: Materials Characteristicsmentioning

confidence: 99%

“…Piezoelectricity has been described as coupling between a quasi-static electric field and dynamic mechanical motion. Equation (1) below represents constitutive (51) equation of linear piezoelectricity and is based on principle of energy conservation. www.intechopen.com where and are stress and strain tensors that satisfy the condition of symmetry, respectively, and and represents electric flux density and the electric field, respectively.…”

Section: Simple Quantitative Theory Of Piezoelectricitymentioning

confidence: 99%

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Ceramic Based Intelligent Piezoelectric Energy Harvesting Device

Patel¹

2011

Advances in Ceramics - Electric and Magnetic Ceramics, Bioceramics, Ceramics and Environment

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“…Fluoropolymer piezoelectric charge electrets are also considered in [14,15], with a maximum d 33 = 150 pC/N [15]. The concept of the piezoelectric charge electret, as shown schematically in Fig.…”

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confidence: 99%

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

Neugschwandtner¹,

Schwödiauer²,

Bauer‐Gogonea³

et al. 2000

Appl Phys A

102

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Large piezoelectric d 33 coefficients around 600 pC/N are found in corona-charged non-uniform electrets consisting of elastically "soft" (microporous polytetrafluoroethylene PTFE) and "stiff" (perfluorinated cyclobutene PFCB) polymer layers. The piezoelectric activity of the twolayer fluoropolymer stack exceeds the d 33 coefficient of the ferroelectric ceramic lead zirconate titanate (PZT) by more than a factor of two and that of the ferroelectric polymer polyvinylidene fluoride (PVDF) by a factor of 20. Soft piezoelectric materials may become interesting for a large number of sensor and transducer applications, in areas such as security systems, medical diagnostics, and nondestructive testing. 77.84.Jd; 85.50.+k Piezoelectricity is the basis for a large number of sensor and transducer applications. Mass products emerge in security systems, medical diagnostics and nondestructive testing [1]. Basic science benefits from resonant ultrasound spectroscopy for the determination of acoustical properties of materials with sample masses of only a few µg [2]. Sensitive and low-cost piezoelectric materials are in high demand for these applications. In this rapid communication, very large piezoelectric coefficients are reported in charged heterogeneous electret films, surpassing all materials known so far. A heterogeneous two-layer electret stack, based on exceptionally stable fluoropolymer charge electrets is proposed and experimentally demonstrated. Preliminary results indicate not only very large, but also long-term stable piezoelectric effects, most promising for applications in sensor and transducer devices. PACS:Piezoelectric material constants relate second-order symmetric tensors (stress T or strain S) to vectors (displacement D or electric field E). Since electric field and stress are independent variables easily to control experimentally, the most often used piezoelectric tensor is the third-rank d-tensor relating displacement D and stress T (direct piezoelectric effect) or strain S and electric field E (inverse piezoelectricIn piezoelectric sensors and thickness mode resonators, the d 33 coefficient is employed, 3 denotes the polar axis and the contracted notation is used. A necessary condition for the occurrence of piezoelectricity is the absence of a center of symmetry, piezoelectric materials are therefore intrinsically anisotropic. Large piezoelectric coefficients are usually found in ferroelectric crystals and polymers. The most widely employed piezoelectric material, lead zirconate titanate (PZT), with a composition near the morphotropic phase boundary between the rhombohedral and tetragonal phase shows a d 33 coefficient of 220 pC/N [4]. Since the use of lead-containing materials is environmentally hazardous, the development of new piezoelectric materials is a matter of urgency. For a large number of applications, e.g. in medical ultrasound, low-density piezoelectric materials (such as polymers) are interesting, with an acoustic impedance matched to that of the human body. Unfortunately, the d 33 coeff...

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Piezoelectricity of porous polytetrafluoroethylene single- and multiple-film electrets containing high charge densities of both polarities

Cited by 78 publications

References 1 publication

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

Ceramic Based Intelligent Piezoelectric Energy Harvesting Device

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

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