Giant dielectric response and grain heterogeneity of Y2/3Cu3Ti4O12–TiO2 composite ceramics fabricated by hydrothermal process

Due to the boom of the electronic information industry, dielectric ceramic materials are widely applied in passive components such as multilayer ceramic capacitors. In this article, Y2/3Cu3Ti4O12–TiO2 composite ceramics with outstanding dielectric properties (εr = 2.29 × 106 at 20 Hz, εr = 4.49×105 at 1 kHz) were successfully prepared by hydrothermal and in situ solid‐state methods. The minimum dielectric loss value (at 1 kHz) of the obtained composite ceramics is about 0.57. The experimental results show that Y2/3Cu3Ti4O12 has a composite perovskite structure with cation vacancies, which causes internal electron‐pinned defect‐dipole, and the easy entry of excessive titanium ions to produce donor defects. Meanwhile, the heterogeneous grains with a pomegranate‐like microstructure were observed in the prepared composite ceramics, and interfacial polarization between subgrain boundaries was substantiated by impedance analysis. The abundant weakly trapped electrons and more polarized interfaces formed by grain and subgrain boundaries are the primary sources of the excellent dielectric properties of composite ceramics.