Microwave dielectric properties and microstructure of Sm(Mg0.5Ti0.5−xSnx)O3 ceramics

Sm(Mg0.5Ti0.5−xSnx)O3 (x=0.1–0.5) ceramics were prepared by a conventional solid-state ceramic route. The microstructure and microwave dielectric properties were investigated as functions of Sn4+ substitution and the sintering temperature. A pure perovskite structure was obtained for samples with x=0.1–0.4, whereas small amount of second phase Sm2Sn2O7 appears in the sample with x=0.5, which deteriorates the dielectric properties of the ceramics. Sn4+ substitution shows little influence on the sintering densification of the ceramics. With the increase of Sn4+ substitution, the dielectric constant and absolute value of τf for Sm(Mg0.5Ti0.5−xSnx)O3 ceramics decrease and increase, respectively. The Q×f of the ceramics can be improved by appropriate Sn4+ substitution. The Sm(Mg0.5Ti0.2Sn0.3)O3 ceramic sintered at 1625oC for 3 h shows excellent microwave dielectric properties (εr=22.0, Q×f=72300 GHz, τf =−41.8 ppm/°C), indicating that it could be used as a candidate compensate for the material with positive temperature coefficient of resonant frequency.