Enhancement of giant dielectric response in Ga-doped CaCu3Ti4O12 ceramics

The influences of Ga3+ doping ions on the microstructure, dielectric and electrical properties of CaCu3Ti4O12 ceramics were investigated systematically. Addition of Ga3+ ions can cause a great increase in the mean grain size of CaCu3Ti4O12 ceramics. This is ascribed to the ability of Ga3+ doping to enhance grain boundary mobility. Doping CaCu3Ti4O12 with 0.25 mol% of Ga3+ caused a large increase in its dielectric constant from 5439 to 31,331. The loss tangent decreased from 0.153 to 0.044. The giant dielectric response and dielectric relaxation behavior can be well described by the internal barrier layer capacitor model based on Maxwell−Wagner polarization at grain boundaries. The nonlinear coefficient, breakdown field, and electrostatic potential barrier at grain boundaries decreased with increasing Ga3+ content. Our results demonstrated the importance of ceramic microstructure and electrical responses of grain and grain boundaries in controlling the giant dielectric response and dielectric relaxation behavior of CaCu3Ti4O12 ceramics.