Dielectric response mechanism and suppressing high-frequency dielectric loss in Y2O3 grafted CaCu3Ti4O12 ceramics

Ca1-3x/2Y (x) Cu3Ti4O12 (0 <= x <= 0.67) ceramics were fabricated by a conventional solid-state reaction method. Lattice parameter of the system increases linearly with increasing x. The high-frequency dielectric loss of Ca1-3x/2Y (x) Cu3Ti4O12 is suppressed significantly while the dielectric constant decreases slightly. The dielectric, impedance and modulus spectra reveals that the giant dielectric response associates with the Maxwell-Wagner effect. The decrease of dielectric constant is just related to the capacitance of grain boundaries. The dielectric relaxation behavior of the system is independent of Y substitution while the correlation between conductivity and frequency becomes stronger in Y substituted CaCu3Ti4O12. It suggests that space charge and long-range hopping of carriers play important roles on the low-frequency dielectric properties. The decrease of grain-boundary activation energy with Y substitution indicates that the concentration of oxygen vacancies increases in grain boundaries. The mechanisms of depressing low-frequency dielectric constant and high-frequency dielectric loss was discussed.