Mechanism of Microwave Dielectric Dispersion in Polycrystalline BaTiO₃

Abstract

The frequency dependence and temperature dependence of the dielectric constant, far infrared reflectivities, grain sizes and densities of polycrystalline BaTiO₃, SrTiO₃ and TiO₂ were measured. From the results obtained, it is shown that, in BaTiO₃, the microwave dispersion occurs only in the ferroelectric phase and the dielectric constant at low frequencies corresponds to that under the condition of constants stress. Thus, it is concluded that the microwave dispersion in polycrystalline BaTiO₃ is due to the transition of the dielectric constant from the value at “free” state to that at “clamped” state with increasing frequency, in the neighborhood of the resonance frequencies of piezoelectric vibration of single domains in grains of this material.