Phase transition, microstructure and microwave dielectric properties of α-CaSiO3 ceramics with SiO2 addition

The effect of SiO2 addition on phase transition, microstructure and microwave dielectric properties of α-CaSiO3 ceramics was reported for the first time. The X-ray diffraction analysis confirmed that the phase transformation from cyclo-CaSiO3 to pseudo-CaSiO3 was inhibited with the increase of SiO2 content. It was observed that the average grain size decreased with the increasing addition of SiO2 by scanning electron microscope. The τf of the SiO2-added α-CaSiO3 ceramics almost remained constant with the SiO2 content increased, while the εr and Q × f changed obviously. The optimized properties were determined for SiO2 6 wt% additive α-CaSiO3 ceramics sintered at 1,350 °C: εr = 7.37, Q × f = 33,714 GHz and τf = −11.08 ppm/°C.