Advanced FeTiNbO6/poly(vinylidene fluoride) composites with a high dielectric permittivity near the percolation threshold

Abstract

FeTiNbO6 (denoted as FTN) is a recently discovered giant dielectric material with high Curie temperature (550 K). In this work, well dispersive FTN particles with mean particle size about 500 nm were synthesized by the improved solid-state reaction method. Using FTN particles as fillers and poly(vinylidene fluoride) (denoted as PVDF) polymer as matrix, multi-volume ratio (0%–60%) homogeneous ceramic/polymer composites have been prepared through a hot-pressing technology. At the same filling content, the FTN/PVDF composites display higher dielectric permittivity compared to the normal reported BaTiO3/PVDF composites, even larger than that of PVDF based composites using giant dielectric CaCu3Ti4O12 as filler. Especially, for 40 vol. % FTN/PVDF composites, the dielectric permittivity is as high as 181 measured at 100 Hz and 25 °C. Through the theoretical analysis correlated with structure evolution observation, it is deduced that the high dielectric performance originates from the combined effect of a variety of factors, such as giant dielectric semiconducting FTN particles, the micro-capacitor structure, and percolation phenomenon at appropriate volume fraction of FTN. Moreover, FTN/PVDF composites present strong dielectric relaxation behavior, which results from the superposition of the dielectric relaxation between PVDF and FTN. These flexible, easy processing FTN/PVDF composites with large dielectric permittivity values could find applications as new generational embedded capacitors.