Effects of sintering temperature and annealing atmosphere on microwave dielectric properties of CaCu3Ti4O12, Ba(Fe1/2Nb1/2)O3 and Sr(Fe1/2Nb1/2)O3 ceramics

Microwave dielectric properties of CaCu3Ti4O12, Ba(Fe1/2Nb1/2)O-3 and Sr(Fe1/2Nb1/2)O-3 ceramics were evaluated at 3.4-9.5 GHz, focusing on the effects of sintering temperature and annealing atmosphere. Their dielectric constant showed slight frequency dependence, and was insensitive to the preparing conditions. Their dielectric loss decreased and Qf value increased greatly with frequency, indicating the domination of extrinsic polarization on microwave dielectric loss. Microwave dielectric loss increased significantly with sintering temperature for CaCu3Ti4O12, while the annealing atmosphere had more notable effect on the dielectric loss of Ba(Fe1/2Nb1/2)O-3 and Sr(Fe1/2Nb1/2)O-3, indicating the different extrinsic polarization mechanisms at microwave frequencies for the three ceramics. (C) 2015 Elsevier Ltd. All rights reserved.