LAUSR

Abstract The phase formation, microstructure, chemical structure, and microwave (MW) dielectric properties of the composite ceramics (1- x )Mg (1.04–3/2 y ) Ce y TiO 3 - x CaTiO 3 (MCT-CT) have been investigated systematically. The CaTiO 3 and MgTiO 3 phases coexist well with the formation of secondary phase MgTi 2 O 5 based on X-ray diffraction. Chemical structure analysis reveals the existence of oxygen vacancies ( V O • • ) whose concentrations increase with x , which consequently induce microwave dielectric loss. It has demonstrated that the behaviors of Q×f are influenced strongly by the phase composition and vacancy defects. Although an increasing amount of CaTiO 3 can improve the dielectric constant (e r ) of the sample slightly, it renders a decrease in the Q×f value instead. The τ f value is strongly correlated to the compositions and the existing phases that can be controlled. An excellent combination of the MW dielectric properties e r ∼23, Q × f ∼70, 800 GHz, and τ f ∼0 ppm/°C was obtained at x =0.08, sintered at an optimal temperature of 1300 °C/3 h.