Microstructural evolution and dielectric properties of SiO2-doped CaCu3Ti4O12 ceramics

The abnormal grain growth (AGG) behavior of undoped and SiO 2 -doped CaCu 3 Ti 4 O 2 (CCTO) ceramics were investigated. With the addition of 2wt.% SiO 2 , the AGG-triggering temperature decreased from 1100 to 1060°C, and the temperature for obtaining a uniform and coarse microstructure decreased from 1140 to 1100°C. The lowering of the AGG temperature by SiO 2 addition was attributed to the formation of a CuO-SiO 2 -rich intergranular phase at lower temperature. The apparent dielectric permittivity of coarse SiO 2 -doped CCTO ceramics was ∼10 times higher than that of fine SiO 2 -doped CCTO ceramics at the frequency of 10 3 -10 5 Hz. The doping of SiO 2 to CCTO ceramics provides an efficient route of improving the dielectric properties via grain coarsening. The correlation between the microstructure and apparent permittivity suggests the presence of a barrier layer near the grain boundary.