  Based on the two-step-switching model, the process of electromechanical
poling of a ferroelectric ceramics is simulated. A difference of the remnant
polarizations between two poling protocols (mechanical stress is applied before
and after the application of poling field) is found from our simulations, which
is also observed in experiment. An explanation is given to illustrate why the
remnant polarization for the case that mechanical stress is loaded after the
application of electric field is larger than the case that mechanical stress is
loaded before the application of electric field. Our simulation results supply
a proof for the validity of the two-step-switching model in the
electromechanical poling of polycrystalline ferroelectric ceramics.
