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 degrees C can cause an increase in the mean grain size by a factor of similar to 25. The large grained Ca0.98Na0.02Cu3Ti4O12 ceramic exhibits a very high dielectric constant, epsilon'similar to 10(5), at room temperature and over the frequency range of 10(2)-10(5) Hz. Very high epsilon' values with temperature coefficient less than +/- 15% were observed in Ca0.98Na0.02Cu3Ti4O12 ceramics in the range of -70-100 degrees C. The effect of Na doping on the giant dielectric relaxation behavior can be well explained by the Maxwell-Wagner polarization relaxation model. (C) 2013 Elsevier B.V. All rights reserved.