Dielectric properties of BaTiO3-based ceramics measured up to GHz region

A new measuring method and analyzing procedure were proposed to determine the complex dielectric constant of materials with relatively high dielectric constant by a lumped impedance measurement using impedance analyzer. Samples used for the measurement were (Ba_0.6Sr_0.4)TiO₃ (BST) and Ba(Zr_0.25Ti_0.75)O₃ (BZT) ceramics. Micro planar electrodes were formed on the surface of samples by electron beam lithography followed by lift-off method. Complex admittances of these samples were measured up to 3 GHz at different temperatures. Electromagnetic simulations were performed for determining the relative dielectric constant and dielectric loss. The complex dielectric constant vs frequency curves of Ba(Zr_0.25Ti_0.75)O₃ showed a broad dielectric relaxation, while that of (Ba_0.6Sr_0.4)TiO₃ was almost flat up to 3 GHz on high-temperature side of T _m at which dielectric constant shows maximum value. Dielectric dispersion properties were discussed from the viewpoint of diffuse phase transition in ferroelectrics.