Hybrid improper ferroelectric Ca3Ti2O7 (CTO) ceramics were synthesized by a solid‐state reaction method. Their polarization switching currents, dynamic processes of polarization‐switching, and leakage current properties were investigated. It was found that the dynamic polarization curves of CTO ceramics exhibit obvious dependence on the frequency of the driving electric fields. Moreover, CTO ceramics show a switchable diode effect. The underlying mechanism for the observed effects were proposed based on the interplaying between mobile charged defects and bound charges. The charged defects also lead to a decrease in the band gap of the CTO ceramic, as revealed by absorption spectrum analysis.

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