Microstructure, dielectric and nonlinear electrical properties associated with sintering conditions in calcium copper titanate ceramics

A series of calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) samples are prepared by a citric acid sol–gel method and the effect of sintering conditions on microstructure, dielectric and nonlinear electrical properties are investigated in detail. Systematical characterizations by both X-ray diffraction and Raman spectra identify the component phases of sintered products, verifying the formation of single phased CCTO if suitable sintering temperature and durations are selected. Well crystallized grains with the size of several microns are attained for the samples sintered at 1020 °C for 5 h, will make a contribution to giant dielectric behavior, evidenced by the highest value of dielectric constant (ε′ > 2.5 × 10⁴) in the frequency range of 10² to 5 × 10⁵ Hz. Dielectric spectroscopy measurements show similar dielectric dispersion for all the samples, which can be well interpreted by the interface polarization from grain boundaries and the bulk effect. Meanwhile, nonlinear electrical behaviors are observed for all the samples, attributing to the Schottky-like electrostatic barriers at the grain boundaries.