Phase field simulations of polarization switching-induced toughening in ferroelectric ceramics

Polarization switching-induced shielding or anti-shielding of an electrically permeable crack in a mono-domain ferroelectric material with the original polarization direction perpendicular to the crack is simulated by a phase field model based on the time-dependent Ginzburg-Landau equation. The domain wall energy and the long-range mechanical and electrical interactions between polarizations are taken into account. The phase field simulations exhibit a wing-shape-switched zone backwards from the crack tip. The polarization switching-induced internal stresses shield the crack tip from applied mechanical loads. A local J-integral is numerically calculated and used as a failure criterion to illustrate the polarization switching-toughening. The result indicates that an applied uniform electric field parallel to the original polarization direction reduces the apparent fracture toughness, while an applied uniform electric field anti-parallel to the original polarization direction enhances it. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.