An Artificially layered perovskite composed of antiferroelectric PbZrO3 and paraelectric BaZrO3 (BZO) was fabricated on LaNiO3∕Pt∕Ti∕SiO2∕Si substrates at 475 °C by radio-frequency magnetron sputtering. It had an (001)-oriented superlattice structure with an average composition of (Pb0.75Ba0.25)ZrO3 (PBZ). X-ray diffraction, cross-sectional transmission electron microscopy, and a depth profile of a secondary-ion mass spectrometer confirmed the formation of superlattice structure with designed composition modulation. Ferroelectricity was induced in the superlattice films, and the ferroelectric as well as the dielectric properties were enhanced with reducing the stacking periodicity. The remanent polarization Pr and coercive field Ec were found linearly dependent on the applied voltage but independent of the measurement temperature up to 100 °C. The retention loss of superlattice films was small and significantly less than that of (Pb1−xBax)ZrO3 (PBZ) solid-solution films either at room temperature or 100 °C. The dielectric constant of the superlattice films was also found insensitive to temperature up to 175 °C, but not for the PBZ solid-solution film, which exhibited a clear dielectric maximum at the Curie temperature of 125 °C. Moreover, a significant suppression of leakage current down to 10−8–10−9A∕cm2 was obtained in the superlattice films constructed with the wide-bandgap sublayer of BZO.
A constrained ferroelectricity is found in the (001)-textured PbZrO3∕BaZrO3 superlattice films having an average composition of (Pb0.75Ba0.25)ZrO3, which is characterized by the linear dependence of remanent polarization (Pr) and coercive field (Ec) on the applied voltage and its stability against temperature change up to 100°C. A model based on equilibrium of electrostatic energy in dielectric stressing of the superlattice and polarization switching in the ferroelectric sublayer is proposed. The dielectric constant evaluated from a fitting of the measured Pr and Ec relations to the model is consistent to that obtained from impedance measurement. The thermal stability of this “linear” ferroelectricity can be also explained by the temperature-insensitive permittivity of the superlattice films, according to the proposed model.
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