Impedance studies of free-standing, flexible thin films of PVDF filled with gallium nitride nanoparticles

Flexible, free-standing composite films of poly(vinylidene fluoride) (PVDF) with Gallium Nitride (GaN) as fillers, in varying concentrations, were synthesized by sol-gel method. Modulations in the microstructural, morphological and dielectric properties, due to the addition of fillers, were investigated. Modifications in the spherocrystal structure, their dimensions and their number density were observed. Microstructural studies confirmed the presence of GaN nanoparticles in the matrix. FTIR and Raman spectroscopy revealed the presence of the three polymorphs of PVDF in the composite films. The dielectric constant of the composite films were found to increase with the increase in the filler concentration, to almost similar to 6 times that of the value for the pristine film due to the interfacial polarization playing between the polymer chains and the filler nanoparticles. Low values of dielectric constant at higher frequencies were observed due to the contribution of dipolar polarization. A peak-to-peak voltage of similar to 5.4 V, from a triboelectric nanogenerator fabricated using a 1 wt% composite films, was obtained.