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

Abstract

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.