Modeling of Stable and Unstable Polarization Switching

摘要

We examine the stability of poarization switching in polycrystallien ferroelectric/ferroeleastic materials subject to continuous electromechanical loading. In case of unstable switching, a finite change of remanent polarization or strain results from an infinitesimally small increment of the applied load. A mciromechanical switching model is studied as well as a simple macroscopci boundary vlaue problem in combination with a phenomenological switching law. The micromechancial model of a ferroelastic layered composite is based on an energy switching criterion. Stable response is promoted by (i) homogeneity of mechanical stress, (ii) proximity of local load conditions to mechanical strain control. For the macroscopic boundary value problem of a ferroelectric ring, switching stability depends on the applied load conditions as follows: Charge control results i nstable response; voltage control may initiate unstable switching. For voltage contorl, the mathematical instability disappears if a small amount of ferroelectric "hardening" predicted near the former instability.