Barium titanate and the dielectric response of polystyrene-based composites

Barium titanate (BaTiO₃) is characterized by real permittivity values as high as 10,000, depending upon structure. Consequently, in this work, this material was chosen to serve as a high permittivity filler for polystyrene (PS) based composites. In order to determine the influence of particle dimensions on the permittivity of the composite, the filler size was varied by means of ball milling, from the as-received microscopic filler size, to the mesoscopic and nanometric range. Filler size was measured by scanning electron microscopy (SEM). To explore the influence of fillgrade and particle size on the effective permittivity, a range of different composites was produced and subjected to dielectric spectroscopy. The results obtained were compared with effective medium theories. Since neither the Maxwell Garnet nor Bruggeman equations were able to reproduce the dependency of permittivity on composition seen experimentally, the Lichtenecker Rother equation was chosen and found to provide a good fit for the experimental data.