Polarization Reversal and Double Hysteresis Loop in Copolymers of Vinylidene Fluoride and Trifluoroethylene

Koizumi, Naokazu; Murata, Yukinobu; Tsunashima, H.

doi:10.1109/tei.1986.348913

Cited by 47 publications

(26 citation statements)

References 12 publications

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“…When the applied electric field crosses zero, the 37/63 mol% copolymer returns nearly to a non-polar state whereas the 47/53 mol% copolymer remains in a polar state, as noted by Koizumi et a/. 6 …”

Section: D-e Hysteresis Loopmentioning

confidence: 62%

“…6 reported VDF/TrFE copolymers with VDF content smaller than 50mol% to exhibit a D-E double hysteresis loop, implying a non-polar state between positively and negatively polarized states. They found 7 that X-ray diffraction (110)/(200) changed from a double to single peak when a high electric field was applied and that the structure which gave a double peak corresponds to a non-polar and a single peak to the polar state.…”

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confidence: 98%

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Antiferroelectric-Like Behavior of Vinylidene Fluoride/Trifluoroethylene Copolymers with Low Vinylidene Fluoride Content

Takahashi

Kodama

Nakamura

et al. 1999

Polym J

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ABSTRACT:Yinylidene Fluoride/Trifluoroethylene copolymers with compositions 47/53 and 37/63mol% exhibit a ferroelectric square D-E hysteresis loop at low temperatures (below -40'C) and undergo transition to a paraelectric motional phase near T, = 70"C. At intermediate temperature they exhibit a double-hysteresis loop suggesting that polarization reversal occurs through a non-polar phase. Time domain measurement of polarization reversal shows two-step switching transient consisting of fast depolarization and slow re-polarization processes. The remanent polarization imparted in the ferroelectric phase shows gradual decay on heating and disappears completely well below T,. We conclude that these copolymers take an antifcrroelectric-likc non-polar phase between low temperature ferroelectric and high temperature paraelectric phases.KEY WORDS Yinylidene Fluoride/Trifluoroethylene Copolymer ! Ferroelectricity ! Antiferroelectricity I Double Hysteresis I Switching I Depolarization I Copolymers of vinylidene fluoride (VDF) with trifluoroethylene (TrFE) have attracted much attention for the past fifteen years because of their ferroelectric properties and associated piezoelectric and pyroelectric activities. t -3 Of special importance are copolymers containing 50-80mol% VDF which exhibit fast polarization reversal as well as a clear Curie point Tc. When VDF content exceeds 80mol%, Tc is not observable at atmospheric pressure because it is overtaken by melting. When TrFE becomes a major component, ferroelectricity is obscured and finally disappears in polytrifluoroethylene.The ferroelectric phase of a VDF-rich copolymer consists of all-trans molecules packed in parallel to each other in a pseudo-hexagonal lattice. In the paraelectric phase, molecules undergo active rotational motion by adopting a random sequence ofTT, TG, and TG' bonds. Thus, spontaneous polarization is lost intramolecularly. The transition is of first order judging from thermal hysteresis. The 70/30mol% VDF/TrFE copolymer has Tc at llOoC on heating and 70oC on cooling. As VDF content decreases to 50mol%, thermal hysteresis is lost and the transition becomes second-order.A copolymer with equi-molar composition is complex in that it takes a diffuse phase when cooled from the paraelectric phase. The X-ray diffraction profile associated with (110)/(200) interchain reflections consists of broad double peaks. Tashiro et at. 3 designated such a phase as the "cooled phase" and assigned it to an aggregate of tilted monoclinic crystalline domains connected by gauche or skew bonds. Lovinger et at. 4 and Horiuchi et at. 5 proposed a two-phase structure consisting of well-ordered and less-ordered pseudohexagonal phases. In any case, such a diffuse phase is transformed into a regular ferroelectric phase showing a single (110)/(200) reflection peak by applying a sufficiently high electric field if VDF content is slightly larger than 50 mol%. When VDF content becomes smaller than 50 mol%, the diffuse phase is maintained and ferroelectricity is obscured.Koizumi et at. 6 re...

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Section: D-e Hysteresis Loopmentioning

confidence: 62%

mentioning

confidence: 98%

Antiferroelectric-Like Behavior of Vinylidene Fluoride/Trifluoroethylene Copolymers with Low Vinylidene Fluoride Content

Takahashi

Kodama

Nakamura

et al. 1999

Polym J

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“…The question of presence of two types of ferroelectric phase for this class of polymers is not new and is often discussed by different authors. 2 The facts of occurrence of two dielectric anomalies in copolymers VDF/TrFE 70/30 or specific shape of ferroelectric switching curves 70 are usually used as arguments. These two phases are designated as LT and QL in terminology of Ref.…”

Section: Resultsmentioning

confidence: 99%

Dielectric relaxation in vinylidene fluoride–hexafluoropropylene copolymers

Kochervinskiĭ

Malyshkina

Markin

et al. 2007

J of Applied Polymer Sci

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The molecular mobility in copolymers of vinylidene fluoride-hexafluoropropylene VDF/HFP of 93/7 and 86/14 ratios has been investigated by means of broadband dielectric relaxation spectroscopy (10 À1 -10 7 Hz), differential scanning calorimetry DSC (À100 to 1508C), and of wide angle X-ray diffraction WAXS. Four relaxation processes and one ferroelectric-paraelectric phase transition have been detected. The process of the local mobility b-(at temperatures below glass transition point) is not affected by chemical composition of the copolymer and the formed structure. Parameters of segmental mobility in the region of glass transition (a a -relaxation) depend on the ratio of comonomer with lower kinetic flexibility. a c -relaxation is clearly observed only in VDF/HFP 93/7 copolymer, which is characterized by a higher crystallinity and a higher perfection of crystals of a-(a p -) phase. Diffuse order-disorder relaxor type ferroelectric transition connected with the destruction of the domains in low-perfect ferroelectric phase in the amorphous regions has been detected for both copolymers. An intensive relaxation process (a-process) was observed for both copolymers in high-temperature region. DSC data shows that it falls on the broad temperature region of aphase crystals melting. It is considered to be connected with the space charge relaxation.

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“…One assumption made in the creep scenario is that the amorphous components can take part in the polarization switching. This has been justified by the double hysteresis in slowly crystallized P(VDF-TrFE) [35]. To further prove that the amorphous components take part in the polarization switching, we have measured the piezoresponse hysteresis loops over many random places in an individual P(VDF-TrFE) nanostripe and presented it in Fig.…”

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confidence: 90%

Two-Step Polarization Switching in Ferroelectric Polymers

Jonas

et al. 2015

Phys. Rev. Lett.

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The correlation between hierarchical structures and polarization switching in ferroelectric poly (vinylidene fluoride-ran-trifluoroethylene) has been probed by combining transmission electron microscopy studies with piezoresponse force microscopy observations. Differences are demonstrated between homogeneous and anisotropic thin films with well-defined lamellar orientation, with the later exhibiting quadrangular domain shape and double hysteresis. We propose that the polarization switching within lamella is dominated by domain wall flow motion, while the amorphous components between lamellae impede full polarization switching. The coupling between lamellae is controlled by a creep process. These results and interpretations explain well the seemingly contradicting polarization reversal dynamics reported and offer opportunities to change domain reversal speed by making ferroelectric polymer nanostructures.

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Polarization Reversal and Double Hysteresis Loop in Copolymers of Vinylidene Fluoride and Trifluoroethylene

Cited by 47 publications

References 12 publications

Antiferroelectric-Like Behavior of Vinylidene Fluoride/Trifluoroethylene Copolymers with Low Vinylidene Fluoride Content

Antiferroelectric-Like Behavior of Vinylidene Fluoride/Trifluoroethylene Copolymers with Low Vinylidene Fluoride Content

Dielectric relaxation in vinylidene fluoride–hexafluoropropylene copolymers

Two-Step Polarization Switching in Ferroelectric Polymers

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