Lead-free perovskites based on Na0.5Bi0.5TiO3 (NBT) are being considered as viable alternatives to lead-containing piezoelectric materials. The piezoelectric response of morphotropic compositions of these bismuth-based piezoelectrics during the application of external stimuli are governed by an intrinsic local disorder, ferroelectric and antiferrodistortive instabilities, and domain texturing. Understanding the coupling between these mechanisms is of crucial importance for the development of new, environmentally friendly, piezoelectric materials. In this investigation we applied in-situ transmission electron microscopy and high-energy X-ray diffraction to study the changes in the crystal structure and domain texturing during the application of mechanical stresses and electric fields to the morphotropic composition of (1-x)Na0.5Bi0.5TiO3–xK0.5Bi0.5TiO3 (NBT-KBT) piezoceramics. It was found that the mechanisms involved largely depend on the materials’ initial structural state and that phase transitions and domain texturing dominate the polarization- and strain-driven processes.
Morphotropic phase boundary in NBT-KBT bulk materials were studied by preparing thin cross sections. Samples were prepared via both mechanical polishing and FIB. Using diffraction patterns and dark-field imaging existence of different phases were detected and confitmed.