Abstract Ferroelectric properties of copolymers vinylidene fluoride with trifluoroethylene and tetrafluoroethylene are described special interest in their polarization reversal phase transition behavior. The ferroelectric consists all-trans molecules packed a parallel fashion while adopt irregular TT, TG, T[Gbar] conformations the paraelectric phase. In phase, occurs at very high fields (> 100 MV/m) as result eventual 180° rotations individual chain around axes. switching time ranges from...

Piezoelectric properties of polymeric substances arise from either the poling-induced orientation molecular dipoles (class 1) or uniaxial chiral chain molecules 2). The class 1 polymers include ferroelectric polymers, polar with frozen-in dipole orientation, and composites ceramics. Details poling procedure in representative materials are described, optimum conditions suggested. Resulting piezoelectric pyroelectric activities specified as a function remnant polarization, underlying basic...

Piezoelectric properties have been studied for the composite systems of PZT ceramics and polymers including polyvinylidene fluoride (PVDF), polyethylene (PE), polyvinyl alcohol (PVA). The values piezoelectric constants their temperature frequency dependences were discussed on basis theoretical expressions a two-phase system with spherical dispersions. activity all was mainly ascribed to piezoelectricity ceramics. For PVDF-PZT system, PVDF shown make minor contribution compared that PE-PZT...

Dielectric and piezoelectric responses caused by a high electric field 10-Hz small strain have been simultaneously measured for stretched polyvinylidene fluoride using minicomputer system. The was applied up to 240 MV/m in sinusoidal or triangular wave form the frequency range 10−4–10−2 Hz at temperatures between −100 100 °C. Ferroelectric hysteresis loops were observed even below glass-transition temperature of −60 At 20 °C 120-MV/m gave remanent polarization Pr 50 mC/m2 which resulted...

The complex dielectric, elastic and piezoelectric constants were measured for the composites of epoxy resin ferroelectric PZT ceramics at 10 Hz as a function temperature, magnitudes loss tangents these compared with theoretical predictions. two phase system spherical inclusions expressed in terms properties constituents by use known expressions dielectric constants. observed values d-constant (electric displacement/stress) about 3/4 predicted. In local mode dispersion region near -30°C,...

The linear and nonlinear dielectrical depolarization processes of the copolymer vinylidene fluoride trifluoroethylene have been measured. D vs. E hysteresis loop below room temperature indicates ferroelectricity this copolymer. dielectric anomaly disappearance remnant polarization at T0=70°C suggest that T0 is phase transition from to paraelectricity phase. Results are analyzed on basis Weiss-type semimolecular theory.

Abstract The phase transition in a copolymer of 55% vinylidene fluoride and 45% trifluoroethylene near 70°C has been investigated by measuring the temperature dependence fundamental properties. remanent polarization disappeared 70°C. dielectric relaxation strength showed peak indicating an anomaly time critical slowing down phenomenon. A change crystal lattice spacing associated with strain anomalous specific heat were observed. These results are consistent ferroelectric transition....

Electric-field-induced changes in thickness have been measured interferometrically for thin films of ferroelectric VDF/TrFE copolymers. For sinusoidal fields high enough to induce switching, the strain x direction draws a hysteresis loop butterfly shape while electric displacement D conventional square – E loop. The is shown be proportional 2 . Their ratio gives electrostriction constant κ 33 ranging from -2.1 -2.5 m 4 /C Low-field measurements poled samples with remnant polarization P r...

The ferroelectric switching characteristics of polyvinylidene fluoride have been investigated by the time domain measurement electric displacement under a step-function field up to 200 MV/m at temperatures between −100 and 20 °C. Almost complete reversal polarization is found occur in fairly short if applied sufficiently high. 4 μsec °C increases significantly as either or temperature decreases. rate change greater than associated with single relaxation process. This an indication...

Piezoelectric and pyroelectric properties have been investigated in the 52/48, 65/35, 73/27 mol % copolymers of vinylidene fluoride trifluoroethylene. The transverse longitudinal piezoelectric constants as well elastic constant were determined for undrawn samples a function remanent polarization Pr created by room-temperature poling. shows significant increase with increasing Pr. Thus, d (polarization/stress) tends to saturate at high On an assumption isotropy, true e31 e33...

The measurement of the temperature dependence elastic, dielectric, and piezoelectric constants for film 55/45% VDF-TrFE copolymer suggests that Curie exists at about 70 °C. lattice spacing sharply changes a range from 55 to 75 remanent polarization is also determined D versus E hysteresis loop below It found spontaneous strain in crystal linearly related square polarization. transition ascribed electrostriction due dipolar orientation.

Experimental procedures and exemplifying results are described in relation to a nonlinear dielectric investigation of ferroelectric polymers. The apparatus developed here was used apply sinusoidal electric field detect fundamental higher harmonic displacements with 0.01% accuracy by means digital sampling Fourier transform techniques. Three types experiments were made for PVDF. Measurements at relatively low fields determined the constants that second-order constant shown reflect polarity...

Ferroelectric switching characteristics of VDF/TrFE copolymers have been investigated over the entire range composition for samples subjected to drawing and/or annealing. Switching phenomena were most remarkably observed in containing 50–80 mol% VDF. The as-cast copolymer exhibits no behavior because high a depolarization field associated with low crystallinity. Draw-induced orientation chain axis parallel film surface causes an increase amount reversed polarization. Annealing at temperature...

Abstract The phase transition and polarization reversal in a copolymer of 65 mol% vinylidene fluoride 35 trifluoroethylene are examined the light phenomenological theory. free energy function expanded even powers determined from remanent polarization, point reciprocal permittivity. linear coefficient takes value common to order-disorder type ferroelectrics. negative sign first nonlinear indicates that is order. causes an anomaly equilibrium kinetic coefficient, on other hand, shows no which...

Polyimide (PI) is a candidate material that showing promise for use in wide range of applications several advanced technologies. In this study, we employed the reprecipitation method and subsequent imidization to prepare unique hollow PI nanoparticles (NPs) by blending suitable polymer porogen with precursor form individual NPs. The structures were induced through phase separation between porogen, process was influenced compatibility two polymers. We then assembled multilayered films...

Ferroelectric switching characteristics have been measured in the 65/35-mol % copolymer of vinylidene fluoride and trifluoroethylene by applying a step-function high electric field up to 100 MV/m at temperatures between −80 90 °C. The amount reversed polarization is 160 mC/m2 being independent applied temperature. time τs follows an exponential law with activation ranging from 0.8 1.8 GV/m. Extrapolation infinite yields ∼1 nsec. Observed transients were fitted function, 1−exp[−(t/τs)n]. It...

Abstract Copolymers of vinylidene fluoride (VDF) and trifluoroethylene (TrFE), with more than 50 mole percent VDF exhibit D-E hysteresis loops at room temperature which are much sharper those exhibited by various crystal phases the PVDF homopolymer. For copolymer samples investigated here, appreciable conductivity develops elevated temperatures in presence electric fields leads to trapped charges polymer film. These then prevent switching dipoles values that were previously applied, is...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDielectric hysteresis and nonlinearity in a 52/48 molcopolymer of vinylidene fluoride trifluoroethyleneT. Furukawa, A. J. Lovinger, G. T. Davis, M. BroadhurstCite this: Macromolecules 1983, 16, 12, 1885–1890Publication Date (Print):December 1, 1983Publication History Published online1 May 2002Published inissue 1 December 1983https://pubs.acs.org/doi/10.1021/ma00246a015https://doi.org/10.1021/ma00246a015research-articleACS PublicationsRequest reuse...

Abstract Some electrical phenomena in amorphous and partially crystalline polymers are studied. The phenomenologically similar to those materials, but their origin is concluded be space charges embedded polymers. Voltage induced across the surfaces of polymer films, i.e., polystyrene, poly(methyl methacrylate), polyethylene, polypropylene, when they vibrated elongation (elongational piezoelectricity) bending (bending piezoelectricity). former attributed a charge distribution which...

A new class of polymer electrolytes, consisting poly(ethylene carbonate) (PEC) and metal salts, is expected to find application in all‐solid‐state batteries because its excellent performance as an electrolyte. To study the ion‐conductive mechanism PEC‐based broadband dielectric spectroscopy used analyze correlation between relaxation ionic conduction PEC‐lithium bis‐(trifluoromethanesulfonyl) imide electrolytes over a broad range salt concentration (0–150 mol%) at 40 °C. The PEC system has...