Single crystals of superlattice-structured ferroelectrics composed of Bi4Ti3O12 and PbBi4Ti4O15 were grown and the properties of polarization hysteresis and leakage current along the a-axis were investigated. Oxidation treatment led to a marked increase in leakage current at room temperature, showing that electron hole acts as a detrimental carrier for electrical conduction. A well-developed polarization hysteresis with a remanent polarization of 41 mu C/cm(2) was observed, which is suggested to originate from the peculiar ferroelectric displacement of Bi in the Bi2O2 layers.