Microstructural evolution and dielectric properties of SiO2-doped CaCU3Ti4O12 ceramics

The abnormal grain growth (AGG) behavior of undoped and SiO2-doped CaCu3Ti4O12 (CCTO) ceramics were investigated. With the addition of 2 wt.% SiO2, the AGG-triggering temperature decreased from I 100 to 1060 degrees C. and the temperature for obtaining a uniform and coarse microstructure decreased from 1140 to 1100 degrees C. The lowering of the AGG temperature by SiO2 addition was attributed to the formation of a CuO-SiO2-rich intergranular phase at lower temperature. The apparent dielectric permittivity of coarse SiO2-doped CCTO ceramics was similar to 10 times higher than that of fine SiO2-doped CCTO ceramics at the frequency of 10(3)-10(5) Hz. The doping of SiO2 to CCTO ceramics provides an efficient route of improving the dielectric properties via grain coarsening. The con-elation between the microstructure and apparent permittivity suggests the presence of a barrier layer near the grain boundary. (c) 2007 Elsevier Ltd. All rights reserved.