Evaluation of dielectric models for ceramic/polymer composites: Effect of filler size and concentration

All models predict an increase in dielectric constant with increasing filler content. On the other hand, this increase is different for different models, showing the relative importance of the different interactions. Experimentally, the size of the inclusions plays an important role in determining the dielectric behavior of a composite, especially at the nanoscale. Effects occurring at the interface between the filler particles and the matrix become important as the relative surface area at the interface increases. Models not including fitting parameters do not properly represent the increase in dielectric constant with increasing filler content and none of them seem to properly represent the dielectric behavior of nanocomposites. In this way, the effects contemplated by the models - interactions between the particles, interactions with the field, depolarization factor or shape parameter - are not sufficient to account for the variations of the dielectric behavior related to the sizes of the particles.