Study of the dielectric properties of barium titanate–polymer composites

A comparative study of complex dielectric properties has been carried out at the X-band of microwave frequencies of composites of barium titanate (BaTiO3) with two different polymer matrices: insulating polyaniline (PANI) powder (emeraldine base) and maleic resin. From these studies, it is observed that the composites of BaTiO3 with maleic resin show normal composite behavior and the dielectric constant follows the asymmetric Bruggeman model. In contrast, the composites of BaTiO3 with PANI show an unusual behavior wherein even at a low concentration of PANI (5 wt.%) there is a drastic reduction in the dielectric constant of BaTiO3. This behavior of the dielectric constant is explained on the basis of coating of BaTiO3 particles by PANI which in turn is attributed to the highly surface adsorbing character. The materials have also been characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and optical microscopy studies.