Comparative study on dielectric behavior in fresh and aged Na0.5Bi0.5(Ti,Fe,W)O3 thin films

Na0.5Bi0.5(Ti0.90Fe0.02W0.08)O3 (NBTFW) thin film was deposited on the ITO/glass substrate by chemical solution deposition. Microstructure, insulating and dielectric performances were measured and compared in fresh and aged samples. Both samples crystallize into phase-pure perovskite structures and possess smooth surfaces without any cracks. Lower leakage current density and relative dielectric constant can be obtained in aged NBTFW film compared to those for fresh one. At low voltage or high frequency, the fresh film exhibits a typical butterfly pattern of normalized dielectric constant-electric field curve, while the aged film shows an abnormal characteristic with two normal double-peaks shape. The related aging mechanism is discussed to be associated with the realignment of VO⋅⋅−FeTi′ defect dipoles along the spontaneous polarization via the migration of mobile oxygen vacancies.