Effect of lattice orientation, surface modulation, and applied fields on free-surface domain microstructure in ferroelectrics

Ferroelectric perovskites are used in various transducer, memory and optical applications due to their attractive electromechanical and optical properties. In these applications, the ferroelectrics often have complex geometries with a significant portion of the surface free and unshielded by electrodes. The free surfaces play an important role in determining microstructure due to the intricate balance between preferred polarization orientation, mechanical stresses, and stray electric fields that exist outside the specimen. In addition, the stray electric fields at free surfaces are exploited for photochemical reactions and self-assembly. Hence, it is important to predict the domain patterns, stray fields, and mechanical stresses that form in these geometries. We apply a phase-field model in combination with finite-element and boundary-element methods for real-space calculations of microstructure at free surfaces in ferroelectrics. A key advantage of the boundary-element method is that it enables us to calculate the stray electric fields outside the specimen. We examine the effect of lattice orientation, surface modulation and applied far-field stress and electric field on domain microstructure and stray electric fields. 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.