Atmosphere-Engineered PbO x -Mediated Phase Evolution in PZT Thin Films for Enhanced Ferroelectric Performance

Lead zirconate titanate (PbZr1–xTixO3, PZT) thin films are widely used in ferroelectric devices, yet their performance is strongly limited by uncontrolled Pb-related species and oxygen-vacancy defects during crystallization. Here, we demonstrate that the annealing atmosphere governs a unified PbOx-mediated phase evolution mechanism that dictates phase transformation pathways and ferroelectric properties. Systematic comparisons under vacuum, nitrogen, and oxygen reveal that PbOx acts as a dynamic reservoir regulating the competition between pyrochlore stabilization and perovskite nucleation. Vacuum annealing induces severe Pb loss and residual pyrochlore phases, while nitrogen promotes PbOx accumulation but results in oxygen-deficient, defect-rich films. In contrast, oxygen annealing enables simultaneous oxygen-vacancy compensation and PbOx re-integration, leading to complete perovskite formation and enhanced crystallinity. Depth-dependent grazing-incidence X-ray diffraction further uncovers a dual-nucleation mechanism involving interface-driven columnar growth and PbOx-assisted surface nucleation, producing a layered microstructure. Consequently, oxygen-annealed films exhibit superior ferroelectric performance with a maximum polarization of 84.94 μC cm–2 and low coercive field (<40 kV cm–1). Excess oxygen, however, may induce PbO2 formation and secondary phase segregation, indicating the need for balanced atmosphere engineering. This work establishes a general framework for atmosphere-controlled crystallization in ferroelectric oxides via PbOx-mediated phase evolution.