Polarization study of poly(vinylidene fluoride) films under cyclic electric fields

Poly(vinylidene) fluoride (PVDF) is a prototypical piezoelectric polymer, which exhibits a strong piezoelectricity after a poling treatment. In this work, we investigate the polarization behaviors of PVDF film under cyclic electric fields by measuring polarized currents. A compensation method is used to distinguish the polarized current from the capacitive and resistive currents. The PVDF samples with a thickness of 20 or 30 μm and an electrode area of 3 × 3 or 4 × 4 mm 2 are employed, respectively. From the observations, we find that the electrode area does not affect the current density, but a thicker film has a higher residual polarization due to its larger fraction of effective switchable dipoles. The amplitude of the applied field primarily determines the residual polarization. Impressively, an α ‐ to β ‐phase transformation occurs above 225 MV · m −1 and the polarized current reaches the maximum and becomes converges at 350 MV · m −1 . Moreover, a high degree and reproducible residual polarization is obtained through gradually increasing applied field from 50 to 350 MV · m −1 , and the relative standard deviation is 3.74% for 20 available samples. Furthermore, a dipole switching model is used to describe the polarization behaviors of PVDF with a form of f ( E ) = Ae − B | E + C | and the fitting parameters give a further illustration of polarization behaviors in PVDF. POLYM. ENG. SCI., 60:645–656, 2020. © 2020 Society of Plastics Engineers