Considering the nucleation process was asymmetrical and not synchronous due to the effects of
defects in polycrystalline ferroelectric system, a mulriple Kolmogorov-Avrami-Ishibashi (MKAI) model was
proposed based on the classical KAI model. Moreover, the switching kinetics of Bi3.15Nd0.85 Ti3O12
ferroelectric films was investigated using the MKAI model. The simulation results indicates that the MKAI
model was more consistent and exactly with experimental results.