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

Abstract

In this study, TiO2/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 (TiCu..) through replacement of the Cu2+ positions with Ti4+ ions and the production of numerous weakly trapped electrons. The colossal permittivity (εr = 4.57 × 105 at 20 Hz, εr = 9.86 × 104 at 1 kHz) of TiO2/CCTO composite ceramics closely correlates to the charge accumulation on the hierarchical grain boundary barrier layers.