Giant Electrostriction Enabled by Defect-Induced Critical Phenomena in Relaxor Ferroelectric Polymers

Abstract

Polymers that generate large shape changes under electric stimulation are of great interest for many applications. Recently, it was shown that converting a small amount of chlorofluoroethylene (CFE) in relaxor ferroelectric poly­(vinylidene fluoride–trifluoroethylene–CFE) (PVDF-TrFE-CFE) terpolymer into fluorinated alkyne (FA) creates P­(VDF-TrFE-CFE-FA) tetrapolymers with giant electromechanical (EM) response at ultralow electric fields (<50 MV/m). We investigate the microscopic origin of this effect and show that converting the bulky CFE into small-size FA defects dramatically weakens the relaxor behavior. Importantly, P­(VDF-TrFE-CFE-FA) tetrapolymers with near 2 mol % FA exhibit a diffused critical endpoint transition region at which the energy barriers for switching from nonpolar to polar molecular conformations become small. Consequently, a small change of the electric field induces a large electroactuation, which can enable novel applications. This work opens up a totally new approach to designing ferroelectric polymers that generate large responses at ultralow electric fields.

Recent Progress on Structure Manipulation of Poly(vinylidene fluoride)‐Based Ferroelectric Polymers for Enhanced Piezoelectricity and Applications

“…[47] The working mechanism of this method is shown in Figure 5e, [48] where a voltage generator applies an electric field to the piezoelectric material, and then the induced strain is detected by a high-resolution displacement sensor, such as the photonic sensor (or called Fotonic sensor, MTI optical fiber measurement system, fiber-optic probe), [48][49][50] laser displacement sensor (or called laser Doppler vibrometers), [51,52] and linear variable differential transformer (LVDT). [29,53] Generally, two different inverse piezoelectric coefficients are obtained from the S-E loops, i.e., the d ij calculated as the slope the S-E loops at low electric fields (below the coercive field, E c ), [30,36] and the largesignal d ij * measured at high electric fields using the equation, [47] d ij * = S max /E max , where S max and E max are the maximum strain and the maximum electric field, respectively. The d ij is accurate to evaluate the intrinsic piezoelectricity.…”

A self-actuated electrocaloric polymer heat pump design exploiting the synergy of electrocaloric effect and electrostriction

“…This reveals that the polarization of the tetrapolymer peaks at the terpolymers with 1.9 mol% FA-the same composition of the ECE peak. The peak position of polarization also suggests that 1.9 mol% FA tetrapolymer locates at a composition that close to the end critical point, which is considered as an efficient approach to enhance EM and EC performances of ferroelectric relaxors [28][29][30][31]. ∆S and P data were used to determine the phenomenological β coefficient, ∆S = 1 /2 β P 2 (figure 1(e)).…”

Electron-beam writing of a relaxor ferroelectric polymer for multiplexing information storage and encryption

“…12 Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CTFE)) is a chemically inert material, and its domain-controllable strategies are complicated and tedious for chemical modifications. [13][14][15][16] Several efforts have been devoted to patterning ferroelectric polymer nanostructures using highresolution and well-defined anodic aluminum oxide (AAO) molds 17,18 or a hundred-nanometer-level silicon mold. 19,20 Nanoconfined crystallization in the mold is conducive for the formation of one-type orientation domains, thus showing excellent data storage behavior for single-dimensional FeRAM.…”