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

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 (SrTiO 3 ) is considered to be a model system for this examination. Although SrTiO 3 is an intermediate compound between SrO and TiO 2 , the solubilities of SrO and TiO 2 in SrTiO 3 are extremely low. Excess SrO and excess TiO 2 lead to the formation of second phases as Sr 3 Ti 2 O 7 and TiO 2 , respectively, within SrTiO 3 . TiO 2 exists as particulates, and its presence marginally affects the microwave dielectric properties of SrTiO 3 . The Sr 3 Ti 2 O 7 lamella is located on the long axis of the elongated SrTiO 3 grain. With the formation of the Sr 3 Ti 2 O 7 lamella, the permittivity decreases, and the product of quality factor and resonant frequency increases.