Giant dielectric response and nonlinear electrical behaviors of TiO2/CCTO composite ceramics with pomegranate-like microstructure

In this study, TiO 2 /CCTO composite ceramics with pomegranate-like grains were successfully prepared using a novel route. In addition, their microstructures, giant dielectric mechanisms, and nonlinear electrical behaviors were studied in detail. Analyses of the experimental results showed that the grains with a pomegranate-like microstructure had nano/micro-scale grain boundaries, which significantly increased the interfacial polarization at the grain and subgrain boundaries. Simultaneously, impedance analysis corroborated the existence of a low resistance region in the grain interiors. This resulted from the establishment of donor defects ( T i C u .. ) through replacement of the Cu 2+ positions with Ti 4+ ions and the production of numerous weakly trapped electrons. The colossal permittivity (ε r = 4.57 × 10 5 at 20 Hz, ε r = 9.86 × 10 4 at 1 kHz) of TiO 2 /CCTO composite ceramics closely correlates to the charge accumulation on the hierarchical grain boundary barrier layers.