Dielectric studies of polystyrene-based, high-permittivity composite systems

In this paper, we report on a dielectric study of a series of composite systems based upon a polystyrene matrix (έ_m ~2.7) containing dispersed particles of lead zirconate titanate (PZT) and barium titanate (BaTiO₃) (in both cases, έ_p ~1000). These components were chosen to give a high dielectric contrast within the system and, because polystyrene is readily etched using permanganic reagents, the size and distribution of particles within the matrix could be readily determined by scanning electron microscopy. We report on the effect of composition on the effective permittivity of the composite; the precise composition of each system was determined by thermogravimetric analysis. The results obtained are compared with theoretical models. We show that, in systems with high dielectric contrast between the matrix and the particles, the variation in relative permittivity with filler loading is best described by the Lichtenecker Rother model.