Changes in the polarization–field hysteresis loop were systematically investigated for Pb(Zr0.4Ti0.6)O3 capacitors after forming gas annealing at 200 °C. Voltage shift in hysteresis was strongly dependent on the polarization states and ascribed to an asymmetric distribution of defect charges and pinned defect dipoles. Field recovery of the imprinted capacitors and increase in coercive field after the recovery were discussed in conjunction with reversible defect dipoles. From the relaxation of the voltage shift with an activation energy of 0.21 eV, it is inferred that charge trapping may be the main cause of the voltage shift and the subsequent degradation of the capacitors by pinning the polarization and defect dipoles.

Effects of forming gas annealing (FGA) were investigated on ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films fabricated by a chemical solution deposition. With the FGA up to 350 °C, the Pt/BLT/Pt capacitors showed good ferroelectric characteristics without significant degradation. As the FGA temperature was increased, a decomposition of the BLT powder sample was observed by using thermogravimetric analysis. By comparing the time-dependent weight loss of BLT with that of Bi4Ti3O12 during FGA, La doping was found to significantly impede the decomposition rate. The decomposition, especially in the (Bi2O2)2+ layers, was discussed as a hydrogen-induced degradation mechanism in the Bi-layered perovskite ferroelectrics.

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