Evolution of Rayleigh constant in fatigued lead zirconate titanate capacitors

The capacitance of Pt/PbZr_0.5Ti_0.5O₃/Pt capacitors versus the strength of applied ac electric field E has been measured for samples that fatigued at different square pulse switching cycles. Based on the in-series capacitor model, the variation of interface capacitance and bulk ferroelectric capacitance at different stages of fatigue were treated separately. A simplified method was derived to calculate the initial dielectric constant and Rayleigh constant for the bulk ferroelectric film from the ac electric field dependence of the sample capacitance. It was found that the initial dielectric constant and Rayleigh constant for the bulk ferroelectric film changed a little when the number of cycles is less than 3×10 ⁶, whereas it decreased remarkably when the number of cycles is greater than 3×10⁶. The suppression of polarization was attributed to pinning of the domain walls at the electrode/ferroelectric interface.