Piezoelectric response of charged non-180° domain walls in ferroelectric ceramics

Charged domain walls may have lower energy than charge neutral walls when large amount of aliovalent doping are present or when there are substantial amount of charged defects in the system. Charged domain walls can produce much larger contribution to functional properties than charge neutral domain walls because they are energetically less stable. If there are regions of charged domain walls in ferroelectric ceramic, it can enhance the extrinsic contribution to the piezoelectric and dielectric properties. We have performed a theoretical analysis on charged domain walls based on the time dependent Landau-Ginzburg model, assuming there are charge defects from aliovalent doping to locally stabilize such charged domain walls. Using BaTiO3 and PZT as examples, we have studied the stability of charged walls with defect density and found that piezoelectric properties can be greatly enhanced by charged walls if the charge density rho is lower than the charges needed to produce local charge balance. If the charge density is equal or more than the amount needed for electrical balance, the walls are pinned, which causes the reduction of piezoelectric effects. (C) 2012 American Institute of Physics. [doi:10.1063/1.3679084]