Double ferroelectric‐to‐paraelectric transition in 70/30 vinylidene fluoride‐trifluoro ethylene copolymer as revealed by dielectric spectroscopy

Abstract

The variation of dielectric properties with temperature in the 1 kHz to 1 GHz frequency range for the 70/30 copolymer of vinylidene fluoride with trifluoroethylene has been associated to two processes: the β relaxation process associated with the glass transition of the amorphous phase and the ferroelectric‐to‐paraelectric crystal transition. The β process follows a Vogel‐Fülcher behavior exhibiting an anomaly in the vicinity of the crystal transition. Analysis of the ferroelectric‐to‐paraelectric Curie transition reveals the existence of a double relaxation maximum in the dielectric losses. Results have been interpreted in terms of the Havriliak‐Negami relaxation function. The variation of the relaxation strength and of the broadening parameter has been investigated as a function of temperature. The obtained results are discussed in terms of a two‐step phase transformation mechanism for the Curie transition: a first transition from the low temperature “all‐trans” ferroelectric phase to a more defective phase; a second transition from the latter phase to the final paraelectric structure. © 1994 John Wiley & Sons, Inc.

Ferroelectricity and molecular dynamics of poly(vinylidenefluoride-trifluoroethylene) nanoparticles

“…. This can be attributed to the segmental relaxation associated to the glass transition in agreement with previous reports [41][42][43]. In this type of polymers the segmental relaxation has been labeled as β-relaxation since dynamical mechanical analysis shows another relaxation, labeled originally as α, associated to the crystalline phase appearing at higher temperatures [41,42].…”

“…A dramatic increase of the intensity of the relaxation is observed as the ferroelectric-paraelectric transition is approached. It has been proposed that for this type of copolymers the intense relaxation observed centered around 10 8 Hz appears as a consequence of the onset of rotational motion of the molecules within the paraelectric crystalline phase [41,43]. This process coexists with the segmental relaxation, β, occurring in the amorphous phase.…”

“…Broadband dielectric spectroscopy (BDS) can also be used to characterize the ferroelectric nature of P(VDF-TrFE) copolymers [41][42][43][44]. .…”

Pyroelectric polymer electrets

“…Multiple phase transitions were also reported from dielectric measurements by Ezquerra et al [57] and from thermally stimulated depolarization by Faria et al [58]. However, the consequences of these results for the piezo-and pyroelectric response have not been investigated so far.…”

Density Fluctuations and Phase Transitions of Ferroelectric Polymer Nanowires

“…Differentiating Equation 2 with respect to temperature leads to which yields a proportionality between the first derivative of permittivity and the first derivative of density, i.e., ${{\partial {\varepsilon} '} \over {\partial T}} \sim {{\partial {\rho} } \over {\partial T}}$ , and, hence the sensitivity in ${{\partial {\varepsilon} '} \over {\partial T}}$ to accurately describe phase transitions, as exemplified in Figure 2 for PVDF‐TrFE. Numerous dielectric studies on the permittivity of PVDF‐TrFE exist in the literature;25–29 however, the use of the first derivative of ε ′ to assess density fluctuations has not been reported so far.…”