Microstructure and microwave dielectric properties of xSm(Mg _0.5Ti_0.5)O₃-(1 - X)Ca_0.8Sr _0.2TiO₃ ceramics

xSm(Mg_0.5Ti_0.5)O₃-(1 - x)Ca _0.8Sr_0.2TiO₃ (x = 0.50-0.95) ceramics are prepared by a conventional solid-state ceramic route. The microstructure and microwave dielectric properties are investigated as a function of the x-value and sintering temperature. The single phase solid solutions were obtained throughout the studied compositional range. The variation of bulk density and dielectric properties are related with the x-value. Increasing sintering temperature can effectively promote the densification and dielectric properties of xSm(Mg_0.5Ti_0.5)O₃-(1 - x)Ca _0.8Sr_0.2TiO₃ ceramic system. With the content of Sm(Mg_0.5Ti_0.5)O₃ increasing, the temperature coefficient of resonant frequency τ_f value decreased, and a near-zero τ_f could be obtained for the samples with x = 0.80. The optimal microwave dielectric properties with a dielectric constant ε_r of 30.1, Q × f of 115,000 GHz (at 8.0 GHz), and τ_f of 8.9 ppm/°C were obtained for 0.80Sm(Mg _0.5Ti_0.5)O₃-0.20Ca_0.8Sr _0.2TiO₃ sintered at 1,550 °C for 3 h, which showed high density and well-developed grain growth.