Microwave dielectric properties of Ca0.4−xMgxSm0.4TiO3 ceramics

• New dielectric properties of Ca0.4−xMgxSm0.4TiO3 ceramics were investigated.
• With increase of x, the dielectric properties decrease with decreasing tolerance factor.
• An improvement of Q × f value and τf were achieved by Ca0.4−xMgxSm0.4TiO3 system.
• Second phases were formed and affected the dielectric properties of Ca0.4−xMgxSm0.4TiO3 system.
• The εr~55, Q × f ~2000 GHz, and zero τf were obtained for Ca0.2Mg0.2Sm0.4TiO3 ceramics.

Ca0.4−xMgxSm0.4TiO3 ceramics were prepared by the conventional solid-state reaction method to investigate the effects of composition and sintering conditions upon microstructures and microwave dielectric properties. The sintered Ca0.4−xMgxSm0.4TiO3 ceramics have a permittivity in the range 88.3–55, the quality factors from 17,000 to 2000 GHz, and the variation of temperature coefficient of resonant frequency from 135 to −1 ppm/°C with increasing the composition x. The optimized microwave dielectric properties with high dielectric constant of 55, low Q × f value about 2000 GHz, and near zero τf value were obtained for Ca0.2Mg0.2Sm0.4TiO3 ceramics sintered at 1250 °C for 3 h, which was promising candidate as a high dielectric constant, and low Q × f value and τf value microwave material for fabrication of tunable microwave substrates.