Tuning Ferroelectricity in PVDF-TrFE through Thermal Treatment-Dependent Crystal Orientation

The ferroelectric properties of poly-(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) films are critically dependent on its molecular orientation, due to the dipole-electric field match problem. This study systematically investigates the impact of the recrystallization temperature and cooling rate on crystal orientation and resultant ferroelectric performance during melt recrystallization of PVDF-TrFE thin films on mica substrates. The collective analysis of two-dimensional (2D) grazing incidence wide-angle X-ray diffraction (2D-GIWAXD), atomic force microscope (AFM), Fourier transform infrared-grazing incidence reflection absorption spectroscopy (FTIR-GIRAS), and polarization-electric field (P-E) hysteresis measurement data reveals that recrystallization at lower temperatures (25 °C) with a faster cooling rate (100 °C/min) facilitates the formation of edge-on lamellar structures and enhanced ferroelectric performance. During the melt recrystallization of PVDF-TrFE films, mica substrates can promote the formation of more edge-on lamellae compared to glass or silicon substrates. These findings provide an effective approach to modulate the ferroelectric properties of PVDF-TrFE thin films from melt on mica substrates.