Effect of the second phase on the microwave dielectric properties of strontium titanate

Abstract

In this study, the effects of the second phase, either in the form of particulate or of lamella, on the microwave dielectric properties are investigated. Strontium titanate (SrTiO3) is considered to be a model system for this examination. Although SrTiO3 is an intermediate compound between SrO and TiO2, the solubilities of SrO and TiO2 in SrTiO3 are extremely low. Excess SrO and excess TiO2 lead to the formation of second phases as Sr3Ti2O7 and TiO2, respectively, within SrTiO3. TiO2 exists as particulates, and its presence marginally affects the microwave dielectric properties of SrTiO3. The Sr3Ti2O7 lamella is located on the long axis of the elongated SrTiO3 grain. With the formation of the Sr3Ti2O7 lamella, the permittivity decreases, and the product of quality factor and resonant frequency increases.