Ferroelectric domains in PZT ceramics at the morphotropic phase boundary. Can the splitting of reflections in SAED patterns be used for the distinction of different pseudo-cubic phases?

Tetragonal, rhombohedral and monoclinic ferroelectric domains can all occur in morphotropic PbZr_1-xTi_xO₃ (PZT) ceramics. In this article, the influence of these domains on the splitting of reflections in selected area electron diffraction (SAED) patterns along the main pseudo-cubic zone axes is reported. The orientation of the domain wall in a transmission electron microscopy image with respect to the splitting of reflections in the diffraction pattern has to be considered for the interpretation. The distinction of tetragonal and rhombohedral splitting is achieved for a pronounced splitting except for <111> with the domain wall edge on. As the monoclinic structure contains tetragonal as well as rhombohedral distortions, the distinction of monoclinic symmetry from tetragonal and rhombohedral based only on the splitting of reflections is not possible. Conceivable models of configurations of monoclinic subdomains inside the existing tetragonal or rhombohedral microdomains are derived from group-subgroup relations. Some experimental observations are given, which can only be explained by these models.