Dielectric properties of BaTiO3-nylon composites

Barium-titanate-nylon composites have been prepared by mixing finely powdered BaTiO₃ in a viscous solution of nylon dissolved in formic acid. The dielectric constant showed a peak around 40 volume percent composition of BaTiO₃. A comparison of the theoretical density with measured densities showed that the porosity of samples increased with an increasing concentration of BaTiO₃. The dielectric constant was theoretically calculated for a three-phase system i.e., BaTiO₃-nylon and air. The fraction of air was estimated from the difference in the measured and theoretical density. The experimentally observed dielectric behavior could be fitted to the theoretical curve by assuming a lower value for the dielectric constant of BaTiO₃. The lower value of the dielectric constant in finely powdered samples may be caused by the nonferroelectric surface layers of low dielectric constant at the boundary of the crystallites