Effect of electroactive phase transformation on electron structure and dielectric properties of uniaxial stretching poly(vinylidene fluoride) films

Abstract

The effect of stretching conditions, such as stretching ratios, temperatures and rates of extension, on the relative fraction of b-phase and electron structure as well as dielectric properties of poly(vinylidene fluoride) (PVDF) films was investigated. The fraction of b-phase in PVDF film increases greatly and reaches the peak of 93% after uniaxial stretching. Meanwhile, stretched spherulites and micro-strips paralleling with the stretching direction were observed in the matrix by atomic force microscopy (AFM).The results of fine structure of fluorine and carbon elements in PVDF, identified by X-ray absorption near edge structure (XANES), indicate that the coordination between F and H atoms of the adjacent chains is produced and thus enhances the dielectric response of the stretched film. As a result, the dielectric constant of the stretched film increases by 50% and achieves up to 12.1, as well as the dielectric loss being as low as 0.02.

Structural, dielectric and piezoelectric properties of 0–3 PZT/PVDF composites

“…These disadvantages limit their use in applications where flexibility is desired. Polymers such as PVDF are known for their flexibility, mechanical strength, piezoelectric properties and can easily conform to different shapes and structures [6][7][8][9]. The search for the new materials which can combine the complementary features of a polymer and a ceramic has led to the significant research in the field of composite materials [10][11][12][13].…”

Primary and secondary crystallization of fast-cooled poly(vinylidene fluoride) studied by Flash DSC, wide-angle X-ray diffraction and Fourier transform infrared spectroscopy

“…Although the β‐phase holds the thermodynamically most stable zigzag conformation with spontaneous alignment of C − F dipoles perpendicular to the c ‐axis in the crystalline region, PVDF commonly forms α‐phase crystals containing solidified antiparallel dipoles at ambient temperatures, which are bad for its ferroelectric performance. Such a situation can be changed by employing uniaxial stretching, an electric poling field, nucleation substrate, high pressure, nano‐droplets or nano‐clay composites to generate a high content of β‐phase for good ferroelectric performance.…”

Large d33and enhanced ferroelectric/dielectric properties of poly(vinylidene fluoride)-based composites filled with Pb(Zr0.52Ti0.48)O3nanofibers

“…As the breakdown strength decreases dramatically when the volume fraction of PZT nanofibers is larger than 8.7 vol.%, the maximum electric field applicable to the nanocomposites decreases substantially. The β-phase with all-trans bond (TTTT) conformation possess the highest net dipole moment among the four different polymorphs, which displays large piezoelectric and dielectric properties 38 . As seen, when the content of PZT nanofibers is < 5.2 vol.%, the maximum polarization of the composite films increases mildly from ~ 2.1 µC/cm 2 for the pristine PVDF to ~ 2.9 µC/cm 2 at 5.2 vol.% of PZT nanofibers.…”