Aging in Ferroelectrics, a Drift Approach

Point defect migration is considered as a mechanism to yield aging in ferroelectrics. Different from magnetic systems, ferroelectric domains can be pinned by free charges at the perimeter of otherwise homogeneous grains or crystals. This clamping is shown to be stronger due to the reorientation of defect dipoles. Clamping stresses are calculated to be in the range of 10⁶ to 10⁷ Pa in a uniaxial model corresponding to experimental values in the model material BaTiO₃. Their time dependence is given in a uniaxial model case. An extension to three dimensions is discussed. The values are independent of the type of mobile defect charge carrier, electronic or ionic.