High frequency dielectric relaxation in polymers filled with ferroelectric ceramics

We investigated the dielectric relaxation process in high-dielectric constant polymer composite films filled with barium titanate particles. In order to extend the dielectric measurements to the microwave range, we employed a new broadband measurement technique where a thin film capacitance terminating a coaxial waveguide is treated as a transmission line. The complex permittivity, measured at frequencies of 100 Hz to 10 GHz for several films 50 μm to 100 μm thick with a dielectric constant of 3.2 to 30, was fitted to a dielectric model expressed as a superposition of Havriliak-Negami functions. An intrinsic high frequency relaxation process has been identified. It was found that the position of the loss peak depends primarily on the relaxation of the polymer matrix, while its magnitude is amplified by the volume fraction and permittivity of the ferroelectric component.