Variations in the Ferroelectricity and Piezoelectricity of Poly(vinylidene fluoride) Accompanying the Phase Transformation
Kun Liu, Haijun Wang, Mengen Zhao, Yao Wu
Abstract
In this study, the method of coating the surface of α-PVDF films with varying fractions of [BMIM]BF 4 is employed to introduce ion-dipole interaction forces, thereby triggering a solid–solid phase transition to form γ′-PVDF. Furthermore, a detailed investigation was conducted on the effect of the phase transition from α to γ′ on molecular relaxation and ferroelectric, piezoelectric, and dielectric properties. The study revealed that increasing the mass of [BMIM]BF 4 coated on the surface of α-PVDF films could improve the phase transition. However, excessive [BMIM]BF 4 was found to disrupt the surface morphology of the PVDF films. Conversely, limiting the mass of [BMIM]BF 4 applied to the surface facilitated the preservation of an intact surface for γ′-PVDF. Subsequent DMA studies indicated that the phase transition could enhance the interface between the amorphous and the crystalline phases. Achieving the phase transition from α to γ′ allows PVDF to shift from a state of relaxed ferroelectric material to a ferroelectric material, and it also plays a role in elevating piezoelectric performance. Additionally, the ferroelectric and dielectric characteristics show a correlation with the crystallization temperature. As the crystallization temperature decreases, both P max and the dielectric constant exhibit an increase.