Strong domain configuration dependence of the nonlinear dielectric response in (K,Na)NbO₃-based ceramics

The nonlinear dielectric response in (Na_0.52K_0.4425Li_0.0375)(Nb_0.92-xTa_xSb_0.08)O₃ ceramics with different amounts of Ta was measured using subcoercive electric fields and quantified by the Rayleigh model. The irreversible extrinsic contribution, mainly caused by the irreversible domain wall translation, was strongly dependent on the domain configuration. The irreversible extrinsic contributions remained approximately the same within the single-phase regions, either orthorhombic or tetragonal, due to the similar domain morphology. However, in the polymorphic phase transition region, the domain wall density was increased by minimized domain size, as observed by transmission electron microscopy. This resulted in constrained domain wall motion due to self-clamping and reduced the irreversible extrinsic contribution.