Extreme effects of Na doping on microstructure, giant dielectric response and dielectric relaxation behavior in CaCu3Ti4O12 ceramics

Giant dielectric response of CaCu3Ti4O12 ceramics prepared using a solid state reaction method was extremely enhanced by doping with Na ions. Doping CaCu3Ti4O12 with 2.0 at% and sintering at a relatively low temperature of 1030 °C can cause an increase in the mean grain size by a factor of ∼25. The large grained Ca0.98Na0.02Cu3Ti4O12 ceramic exhibits a very high dielectric constant, ε′∼105, at room temperature and over the frequency range of 102-105 Hz. Very high ε′ values with temperature coefficient less than ±15% were observed in Ca0.98Na0.02Cu3Ti4O12 ceramics in the range of −70-100 °C. The effect of Na doping on the giant dielectric relaxation behavior can be well explained by the Maxwell-Wagner polarization relaxation model.