Microstructure and microwave dielectric properties of Bi12SiO20 ceramics

Bi12SiO20 ceramics were well sintered at 800 °C after calcination at 700 °C. A liquid phase of composition Bi2O3 was formed during the sintering at temperatures ≥800 °C and assisted the densification of the Bi12SiO20 ceramics. When the sintering temperature exceeded 800 °C, however, the relative density, ɛr, and Q × f values of the Bi12SiO20 ceramics decreased, probably due to the formation of a large amount of the liquid phase. The Bi12SiO20 ceramics sintered at 800 °C for 5.0 h exhibited excellent microwave dielectric properties with a high ɛr of 43, a high Q × f of 86,802 GHz and a small τf of −10.39 ppm/°C.