Effect of crystalline phase on the dielectric and energy storage properties of poly(vinylidene fluoride)

The crystal structure shows great influence on dielectric and energy storage performance of poly(vinylidene fluoride) (PVDF) films. In this paper, a gamma-phase PVDF film was fabricated by crystallization of PVDF from a DMF solution through a solution-casting method and a quenching treatment. The influences of crystalline phases on the dielectric and energy storage properties of the films were studied. It has been found that, compared with common alpha- and beta-phase, the obtained gamma-phase PVDF film presents much higher relative permittivity of about 9.8 in a 1 kHz electric field. The ferroelectric hysteresis loop investigation indicates that the gamma-phase PVDF film exhibits much slimmer polarization-electric field hysteresis loops than alpha- and beta-phase PVDF films and a high energy efficiency more than 72 % is obtained. This gamma-phase PVDF film also shows low leakage current at high working voltage, which is more desirable and promising for high performance pulse discharge capacitor application.