Complex impedance spectroscopy for capacitive energy-storage ceramics: a review and prospects

For capacitive energy-storage ceramics, the potential of impedance spectroscopy (IS) is difficult to exploit fully because of the relaxation-time complex distributions caused by intrinsic/extrinsic defects. Herein, we briefly introduce theories and techniques of IS. Impedance applications are reviewed from the dipole to device scale according to the carrier displacement, including grain boundary, core-shell structure, local relaxation (dielectric relaxation), and non-local relaxation (long-range conduction). The whole picture is summarized from a novel perspective based on the response of the electroactive area. This reveals the critical role of IS in capacitive energy-storage ceramics. In addition, we point out new development directions and prospects for impedance in capacitive energy-storage ceramics. This review will be an essential milestone in impedance research of energy-storage ceramics and promote the understanding and development of IS.