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The dynamic hysteresis of ferroelectric Pb(Ti0.48Zr0.52)O-3 (PZT) and Bi2Sr2Ta5O9 (SBT) thin films is investigated using the Sawyer-Tower (ST) method, emphasizing the dependence of hysteresis area A against frequency f and amplitude E-0 of applied external electric field. It is revealed that the hysteresis dispersion A(f) under a given E-0 exhibits a single-peaked pattern with power-law tails in the limits of low and high frequency. Based on the mechanism of ferroelectric domain. reversal in which the nucleation and growth sequences occur concurrently, a single-parameter dynamic scaling hypothesis on the hysteresis dispersion is proposed and demonstrated for the two types of ferroelectrics. The effective characteristic time for the domain reversal, inversely proportional to the field amplitude E-0, is predicted. (C) 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.