Polymer composites with the dielectric constant comparable to that of barium titanate ceramics

It has been found that CdO/polymer composites exhibit unusually high dielectric constant, much higher than that of BaTiO3/polymer composites, and comparable in magnitude to the dielectric constant of pure BaTiO3. While the dielectric constant of a BaTiO3/polymer composite at 1 kHz is below 20 at 20% volume fraction of BaTiO3, the dielectric constant of the corresponding 20% CdO/polymer composite is 2200. For both composites the relationship between logarithm of dielectric constant of the composite and volume fraction of the filler is linear within the range of useful filler contents where the composites are easily processable. Extrapolation of the data to 100% of the filler content yields the estimates of effective dielectric constants of pure fillers, which are of the order of 103 for BaTiO3 and 1015 for CdO. Thus, CdO behaves as a material with extremely high dielectric constant, when embedded into a polymer matrix. Preliminary data obtained for another composite based on tungsten dioxide (WO2) indicate that WO2 is another high-k filler.