Dielectric/ferroelectric properties of ferroelectric ceramic dispersed poly (vinylidene fluoride) with enhanced beta-phase formation

Free standing and flexible ferroelectric ceramic-polymer composites (PVDF + Phi wt% of BNBT (0.94Na(0)(.)(5)Bi(0)(.)(5)TiO(3)-0.06BaTiO(3))) with 0-3 connectivity were synthesized by solution-casting technique. Composite nature and homogeneous distribution of ceramic filler particles in PVDF were confirmed with x-ray diffraction and scanning electron microscopic analysis. The intensity ratio of beta-phase with respect to alpha-phase i.e., I-20(.2)./I-18.4. (obtained from XRD analysis) and the fraction of electro-active beta phase i.e., F(beta)% (obtained from FTIR analysis) are enhanced with increase in filler concentrations and peaked for 35 wt% of the ceramic filler. An enhancement of the % of crystallinity (calculated from XRD analysis) has been observed with increase in the filler concentrations. The increase of the fraction of beta-phase has been explained on the basis of ion (negatively charged surface ion of the ferroelectric ceramic filler) -dipole (-CH2 dipole of the polymer matrix) interactions, as evidenced from FTIR and UV-VIS absorbance spectra. Relative dielectric permittivity (dielectric constant) and ferroelectric polarization were found to be highest for the composite with 35 we% of ferroelectric ceramic filler. Percolation theory has been successfully employed to explain the observed trend in the dielectric properties with the compositional variation. Significant enhancement in the electro active beta-phase has been correlated with the improved dielectric and ferroelectric properties of the composite