Microstructure and microwave dielectric properties of Bi12SiO20 ceramics

Bi12SiO20 ceramics were well sintered at 800 degrees C after calcination at 700 degrees C. A liquid phase of composition Bi2O3 was formed during the sintering at temperatures >= 800 degrees C and assisted the densification of the Bi12SiO20 ceramics. When the sintering temperature exceeded 800 degrees C, however, the relative density, epsilon(r), and Q x 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 degrees C for 5.0 h exhibited excellent microwave dielectric properties with a high epsilon(r) of 43, a high Q x f of 86,802 GHz and a small tau(f) of -10.39 ppm/degrees C. (C) 2012 Elsevier Ltd. All rights reserved.