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

The effect of SiO 2 addition on phase transition, microstructure and microwave dielectric properties of α -CaSiO 3 ceramics was reported for the first time. The X-ray diffraction analysis confirmed that the phase transformation from cyclo-CaSiO 3 to pseudo-CaSiO 3 was inhibited with the increase of SiO 2 content. It was observed that the average grain size decreased with the increasing addition of SiO 2 by scanning electron microscope. The τ f of the SiO 2 -added α -CaSiO 3 ceramics almost remained constant with the SiO 2 content increased, while the ε r and Q × f changed obviously. The optimized properties were determined for SiO 2 6 wt% additive α -CaSiO 3 ceramics sintered at 1,350 °C: ε r = 7.37, Q × f = 33,714 GHz and τ f = −11.08 ppm/°C.