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Ferroelectricity has been induced in the quantum paraelectric AgTaO3 (AT) by Li+ substitution, as evidence by both the dielectric anomaly and the hysteretic loop of electrical displacement versus applied electric field. The transition temperature (Tc) of Li-doped AT was found to increase with increasing level of Li+ substitution. Also, by substituting 12 mol % of Li+ into AT, which is close to the solubility limit, a ferroelectric material with a residual polarization ∼15 μC/cm2 and Tc at 258 K was then triggered.

Heterolayered Pb(Zr 0.52 ,Ti 0.48)O 3 /(Bi 3.15 Nd 0.85)Ti 3 O 12 (PZT/BNT) thin films were synthesized via a route of combining sol-gel and rf-sputtering. A fatigue anomaly is observed for the heterolayered PZT/BNT thin films, whereby a switchable polarization peak, which is more than 5 times higher than that of the virgin state, occurs upon polarization switching for 10 8-10 9 cycles. Interestingly it shifts towards smaller numbers of switching cycles at elevated temperatures. Both the aging and dielectric behavior suggests that the fatigue anomaly is related to the defects accumulated at the interfaces in the heterolayers.

Bilayered ferroelectric thin films consisting of Pb(Zr0.52Ti0.48)O3 (PZT) and (Bi3.15Nd0.85)Ti3O12 (BNT) layers have been successfully fabricated via a synthesis route of combining sol-gel and rf sputtering. Both ferroelectric layers are well retained in both PZT/BNT and BNT/PZT bilayered films as suggested by x-ray diffraction and secondary ion mass spectroscopy analyses. Their ferroelectric and dielectric properties are largely dependent on the thicknesses of the constituent layers. An anomalous enhancement in polarization is demonstrated by the PZT/BNT bilayered thin film, whereby the switchable polarization increases dramatically upon >106cycles of polarization switching. The fatigue anomaly observed for the PZT/BNT bilayered thin film is related to the space charges that are accumulated at the interfaces in the heterolayered structure. By comparison, the BNT/PZT bilayered thin film exhibited better ferroelectric behavior than that of the PZT/BNT film where the P-E hysteresis loops were relatively well saturated with higher polarization. The BNT/PZT bilayered thin film also demonstrated a much improvement in fatigue behavior as compared to that of the single layer PZT film.