Study on the enhancement of ferroelectric β phase in P(VDF-HFP) films under heating and poling conditions

Abstract

Free-standing, flexible films of poly(vinylidene fluoride–hexafluoropropylene) (P(VDF-HFP)) were prepared by spin coating technique, and the effects of heat treatment and poling on the formation of electroactive β phase were studied. The X-ray diffraction, Fourier-transform infrared spectroscopy, Field emission scanning electron microscopy and Atomic force microscopy studies proved that the melt-quenching process influences the transformation of non-ferroelectric α phase to ferroelectric β-phase, when compared to heat-drying process. The variation in the β-phase content resulted in the enhanced ferroelectric response in the melt-quenched samples, which was proved by the dynamic contact electrostatic force microscopy (DC-EFM) studies and also by the ferroelectric hysteresis. The polarization switching behavior of the films was also investigated with DC-EFM. The electrical poling at 30MV/m further enhanced the ferroelectric nature of the films by 29–30%. The films exhibited high dielectric constant, low dielectric loss, and low-leakage current, and it was identified that the leakage current in the films was originated due to the Schottky emission.