Ferroelectric domain structures near the MPB in (1-x)Pb(Zn _1/3Nb_2/3)O₃-xPbTiO₃

In (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-xPT), there exists the morphotropic phase boundary (MPB) as an almost temperature-independent boundary around x = 0.10. In order to understand an origin of the excellent piezoelectric response found near the MPB in PZN-xPT, the features of ferroelectric domain structures in the tetragonal side of the MPB have been examined mainly by transmission electron microscopy. The ferroelectric domain structure in x = 0.12 specimens prepared from single crystals as bulk samples was found to be the superposition of the tetragonal domain structure with the [001] polarization and the curved-boundary regions with the [100] or [010] one. On the other hand, the cooling from the paraelectric phase in thin specimens used for transmission-electron-microscopy observation resulted in two types of ferroelectric domain structures. One was the fine {110} banded structure in the fast cooling rate and the other was the maze-pattern structure in the slow rate. These two structures usually coexisted and the volume fraction between them was cooling-rate dependent. In order to understand these curious features, we proposed the domain-structure model based on the aggregation consisting of nano-scale ferroelectric domains.