Effect of TiO2 and CaTiO3 additives on the sintering behavior and microwave dielectric properties of Ca(Mg0.92Al0.08)(Si0.96Al0.04)2O6 ceramics

Ca(Mg0.92Al0.08)(Si0.96Al0.04)2O6 ceramics with different amounts of TiO2/CaTiO3 additions were prepared by the solid-state reaction method. The sintering behavior, microstructure and microwave dielectric properties of TiO2/CaTiO3-added ceramics were investigated. The control of the temperature coefficient of resonant frequency (τf) could be achieved by varying the content of TiO2 or CaTiO3. Particularly, TiO2 reacted with the main ceramic phase of Ca(Mg,Al)(Si,Al)2O6 and produced secondary phases of MgTi2O5 and CaTiSiO4O, which lowered the Q×f values of the ceramics. TiO2-added ceramics sintered at 1225 °C with 22 wt% TiO2 additions showed dielectric properties of εr=12.06, Q×f=5940 GHz and τf=2.24 ppm/oC. Comparing with the TiO2-added ceramics, CaTiO3 just existed as a separate component, and the Ca(Mg0.92Al0.08)(Si0.96Al0.04)2O6 ceramic sintered at 1250 °C with 10 wt% CaTiO3 additions showed a good combination of dielectric properties: εr=9.6, Q×f=32,590 GHz and τf=−1.53 ppm/oC.