A micro-electro-mechanical model for polarization switching of ferroelectric materials

Ferroelectric and ferroelastic switching are the major source of nonlinearity and hysteresis in ferroelectric materials subjected to high electric field or mechanical stress. A computational micromechanics model for polycrystalline ferroelectric ceramics is developed based on consideration of the constitutive behavior of single crystals. This model simulates the tetragonal and the rhombohedral crystal structures. Saturation of the linear piezoelectric effect is included. Interaction between different grains in the polycrystalline ceramic is considered. A switching criterion is developed that accounts for different energy levels associated with 90 degrees and 180 degrees switching for the tetragonal structure (or 70.5 degrees, 109.5 degrees, and 180 degrees for the rhombohedral structure). Experimental results on 8/65/35 PLZT are simulated and a parametric study of the effects of crystal structure, intergranular interaction, and phase transformation is performed. (C) 1998 Acta Metallurgica Inc. Publishcd by Elsevier Science Ltd. All rights reserved.