Ferroelectric domain morphology and structure in Li-doped (K,Na)NbO3 ceramics

We prepared Li-0.02(K0.45Na0.55)(0.98)NbO3 (KNN) ceramics using a conventional solid-state sintering method and investigated the domain structure and morphology using a piezoresponse force microscope in these material systems. The abnormal grain consisted of nano-sized subgrains, which were an elementary unit of the domain formation, with a size of approximately 100 nm. They were self-assembled and grew along the < 001 >(o) directions. In the orthorhombic KNN ceramics, the 90 degrees domains were dominantly distributed and all wedges were 60 degrees wedges. The polarization vectors and geometrical configurations were analyzed and suggested in the banded twins. The observation of angles between (010)(o) and (011)(o) showed that the large grains experienced severe stress resulting in the deformation of the unit cell configuration during the phase transition. The S-walls were preferred as 120 degrees domain walls and were assigned to (1/0.27/1)(c). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746069]