Ferroelectric order and phase transition in polytrifluoroethylene

Oka, Yoshio; Koizumi, Naokazu; Murata, Yukinobu

doi:10.1002/polb.1986.090240912

Cited by 22 publications

(18 citation statements)

References 24 publications

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“…In the range of 30-50 mol% VDF content, copolymers exhibit a double hysteresis loop at room temperature, implying that polarization reversal occurs through a nonpolar state. [4][5][6] It has been shown that the double loop is converted into a ferroelectric square loop as the temperature is decreased. At high temperatures, they undergo transition to a paraelectric motional phase.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Dielectric Investigation of Trifluoroethylene-Rich Copolymers of Vinylidene Fluoride

Kodama¹,

Furukawa²

1999

Jpn. J. Appl. Phys.

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Phase transition behavior in trifluoroethylene (TrFE)-rich copolymers of vinylidene fluoride (VDF) has been investigated by means of nonlinear dielectric spectroscopy. Unlike VDF-rich copolymers showing a single ferroelectric-to-paraelectric transition, TrFE-rich copolymers undergo two-stage transitions, loss of ferroelectric polarization at a temperature T A and transition into a paraelectric motional phase at a temperature T C . Between T A and T C , they exhibit the D-E double hysteresis loop characteristic of an antiferroelectric. Analysis of such a double loop allowed the estimation of antiferroelectric polarization P A as well as ferroelectric polarization P F . A comparison of the temperature dependences of reciprocal polarizabilities β n (n = 1, 2, 3) with those of P F and P A revealed that β 2 is proportional to P F whereas β 1 and β 3 are proportional to P 2 F + P 2 A . These results are consistent with phenomenological prediction for an antiferroelectric. It was concluded that TrFE-rich copolymers of VDF have an antiferroelectric-like phase consisting of all-trans molecules packed in a disordered manner.

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Section: Introductionmentioning

confidence: 99%

Nonlinear Dielectric Investigation of Trifluoroethylene-Rich Copolymers of Vinylidene Fluoride

Kodama¹,

Furukawa²

1999

Jpn. J. Appl. Phys.

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“…8 However, ferroelectricity has been revealed quite recently in the slow-cooled sample and not in the fastquenched sample of PTrFE, which shows behavior similar to that in the low-VDF copolymers described above. 10 As for the effects of quenching on ferroelectric properties in semicrystalline polymers, Tasaka and Miyata studied copolymers of vinylidene fluoride and tetraftuoroethylene (P(VDF /TFE)) and found that a coercive field is higher in quenched samples than in annealed samples. 11 They also found that the coercive field is inversely proportional to the long period.…”

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confidence: 99%

Structure and Spontaneous Polarization in Fast-Quenched Copolymers of Vinylidene Fluoride and Trifluoroethylene

Oka

Murata

Koizumi

1986

Polym J

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ABSTRACT:Fast quenching from the melt was found to effect greatly the structures and ferroelectric properties of vinylidene fluoride and trifluoroethylene copolymers (P(VDF /TrFE)) in contrast to slow cooling. The results are discussed for high-and low-VDF content divided at about 50 mol% VDF. For the high-VDF copolymers, the quenched samples showed high T, like poled samples, implying an ordered ferroelectric phase. Poling the quenched samples at elevated temperatures produced a ferroelectric polarization the direction of which was restored after cooling from above T,. For the low-VDF copolymers, the quenched samples showed a crystalline phase different from that of the slow-cooled samples, which was found to exist in a metastable state. The quenched samples exhibited no ferroelectricity unlike the slow-cooled samples but poling at elevated temperatures induced pyroelectricity with anomalous temperature dependence. From the present results, the fast quenching seems to produce a phase stable at low temperatures and the poling at elevated temperatures causes crystal growth under an electric field resulting in thermallystable spontaneous polarizations. Crystal structures of the low-VDF copolymers are also speculated based on the present results and published structure models.KEY WORDS Vinylidene Fluoride-Trifluoroethylene Copolymers I Fast Quenching I Melt Crystallization I Ferroelectric Phase Transition I Spontaneous Polarization I Pyroelectricity I Copolymers of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)) have been extensively studied since the discovery of ferroelectricity in samples with high-VDF content as the first clear example of a ferroelectric polymer.1.2 Ferroelectricity originates in the structural characteristics of the PVDF form I crystal, namely, the all-trans chain conformation for the highest polarization and the pseudohexagonal chain packing to facilitate chain rotation by 60° steps. 3.4 The high-VD F copolymers are of great advantage to the formation of ferroelectricity because the form I crystal is adopted by as-crystallized samples and a high degree of crystallinity is attained by heat treatment. On the other hand, copolymers with VDF content lower than 50 mol% have been found by our study to exhibit intricate ferroelectric behavior, for example, a D-E double hysteresis loop and an abnormally low amount of remanent polarization. 5 Ferroelectricity is a crystal property which is expected to be strongly effected by a method of melt crystallization in semicrystalline polymers, i.e., slow cooling or fast quenching. We have developed a method of fast quenching * Present address:

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“…Considering thej-E and D-E curvves in Figures 12 and 13, the peak at Eh is due to a polarization process and the peak at E 1 , to a depolarization process. X-Ray diffraction studies under an electric field in previous studies revealed that X-ray patterns at 18-20° in 2 0 changed from single to double peak when the field increased to field E 1 and the pattern changed from a double to single peak when the field further increased to Eh.11- 13 These results were found in the repeated cycles of a high electric filed. Thus, the X-ray pattern gave a single peak at A and a double peak at B or C in Figure 13(a).…”

Section: Crystal Structure Of Slowly Cooled Samplesmentioning

confidence: 89%

“…4 In contrast to copolymers with high VDF content, copolymers with high TrFE content and even PTrFE showed two current peaks in polarization current density j vs. E curves which corresponded to the double hysteresis in D-E curves. X-Ray measurements under high electric field revealed that the two current peaks were related to a phase transition between two slightly different crystal structures.11- 13 These structures were characterized by double and single peaks around 18-20° in X-ray diffraction angle 20 and were referred to as D and S phases, respectively. It was inferred from density and remanent polarization data that molecular chains with T 3 GT3G conformation were packed antiparallel and parallel for the D and S phases, respectively.…”

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Relaxation and Transition of Copolymers of Vinylidene Fluoride and Trifluoroethylene with High Trifluoroethylene Content

Murata

1988

Polym J

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ABSTRACT:Dielectric behavior and related properties were investigated for copolymers of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) with TrFE content from 35 to 87mol%.Three dielectric loss peaks, designated as /3', {3, and T, were observed in increasing order of temperature. The {3' relaxation was predominant in samples with high crystallinity for all copolymers and was connected with molecular motion around defects due to anomalous linkages of head-to-head and tail-to-tail of TrFE rich sequences. The f3 relaxation found in samples with low crystallinity was related to micro-Brownian motion of VDF rich sequences in main chains for 35 to 67mol% TrFE copolymers. In copolymers with 71 and 87mol% TrFE, the f3 relaxation was considered to consist of two components, fJ. and /Jc, due to the local molecular motions in amorphous and crystalline regions, respectively. The T, loss peak was related to a transition between the phase of antiferroelectric nature and paraelectric phase for 48 to 87mol% TrFE copolymers. The transition for 63 and 71 mo!% Tr FE copolymers exhibited characters of the first or second order of the transition, depending on the physical properties observed. Pressure dependence of the T, transition temperature was smaller for 63 and 71 mo!% TrFE copolymers than that for 48 and 35mol% TrFE copolymers.KEY WORDS Vinylidene Fluoride-Trifluoroethylene Copolymer / High Trifluoroethylene Content/ Dielectric Relaxation/ Defect/ Head-to-Head/ Tail-to-Tail / Phase Transition / The relaxation behavior of copolymers of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) with high TrFE content was studied by dynamic mechanical measurements. IX and {3 relaxations due to micro-Brownian motion ofTrFE and VDF rich sequences were found at 313 and 250 K, respectively, for copolymers with 48 to 71 mol% TrFE. 1 Yagi also found two relaxations connected with micro-Brownian motion for copolymers with 40 to 63 mol% Tr FE in dynamic mechanical study. 2 Furukawa et al. 3 studied dielectric behavior of VDF-TrFE copolymers with the entire range of comonomer content and found a relaxation at 253 K at 1 kHz. The relaxation at 253 K was ascribed to the same type of molecular motion in the amorphous region as that of the transformation of trans and gauche at the ferroelectric to paraelectric transition. Koizumi et al. 4 found {3 relaxation due to micro-Brownian motion around 250 K and y relaxation connected with local molecular motion in frozen glassy state at lower temperature. Different relaxation mechanisms were presented for relaxation around 253 K by these authors. For polytrifluoroethylene (PTrFE) two types of relaxation in the crystalline region were found below room temperature and considered to be due to reorientation of main chains around row vacancy defects at chain ends and molecular motion of disordered chains around anomalous linkages such as 771

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Ferroelectric order and phase transition in polytrifluoroethylene

Cited by 22 publications

References 24 publications

Nonlinear Dielectric Investigation of Trifluoroethylene-Rich Copolymers of Vinylidene Fluoride

Nonlinear Dielectric Investigation of Trifluoroethylene-Rich Copolymers of Vinylidene Fluoride

Structure and Spontaneous Polarization in Fast-Quenched Copolymers of Vinylidene Fluoride and Trifluoroethylene

Relaxation and Transition of Copolymers of Vinylidene Fluoride and Trifluoroethylene with High Trifluoroethylene Content

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