Effective enhancement of dielectric properties in cold-pressed polyvinyledene fluoride/barium titanate nanocomposites

Abstract

The dielectric behaviour of a polymer/ceramic composite (PCC) based on ferroelectric polymer [polyvinylidene fluoride (PVDF)] and nano-barium titanate (n-BaTiO3), prepared under the novel cold pressing method, was investigated. Large enhancement of effective dielectric constant (ɛeff ~ 450) with lower loss tangent (tan δ ~ 0.9) at 50 Hz was observed for the PCC with 0.60 as the volume fraction of n-BaTiO3 into the PVDF matrix. The enhancement of ɛeff is attributed to the large interfacial polarisation arising due to the charge storage at the interfaces of the spherulites of PVDF and at the polymer/filler interfaces of PCC. The dielectric results have been explained on the basis of sum effect with the help of the standard Yamada model at 1 kHz, while the low-frequency dielectric behaviour has been explained qualitatively as a combination of both interfacial polarisation at the interfaces of the spherulites and the sum effect of the Yamada model. The achieved lower tan δ for the PCC as compared to the polymer/metal composites (PMC) is attributed to the highly insulating nature of PVDF and semiconducting n-BaTiO3. The thermal stability of the composites is also maintained due to the higher melting temperature (170 °C) of PVDF. The cold-pressed PCC based on PVDF will act as better polymer dielectric for electrical energy storage applications as compared to the reported cold-pressed PMC and the cold pressing may be an effective method of preparation (since the unnecessary introduction of thermal disorder is avoided in this method) in developing polymer dielectrics.