Extreme effects of Na doping on microstructure, giant dielectric response and dielectric relaxation behavior in CaCu_3Ti_4O_(12) ceramics

摘要

Giant dielectric response of CaCu_3Ti4O_(12) ceramics prepared using a solid state reaction method was extremely enhanced by doping with Na ions. Doping CaCu_3Ti_4O_(12) with 2.0 at% and sintering at a relatively low temperature of 1030℃ can cause an increase in the mean grain size by a factor of-25. The large grained Ca_(0.98)Na_(0.02)Cu_3Ti_4O_(12) ceramic exhibits a very high dielectric constant, e'-10~5, at room temperature and over the frequency range of 10~2-10~5 Hz. Very high e' values with temperature coefficient less than ± 15% were observed in Ca_(0.98)Na-(0.02)Cu_3Ti_4O_12 ceramics in the range of-70-100℃. The effect of Na doping on the giant dielectric relaxation behavior can be well explained by the Maxwell-Wagner polarization relaxation model.