Effect of poling on nanodomains and nanoscale structure in A-site disordered lead-free piezoelectric Na_0.5Bi_0.5TiO₃-BaTiO₃

This paper establishes the nanoscale poling mechanism operating in A-site disordered lead-free piezoelectric ceramics. Nanoscale domain maps and quantitative structural changes were obtained by deploying high-resolution transmission electron microscopy, dielectric spectroscopy, Raman spectroscopy and neutron scattering. Based on these results a microscopic model is proposed that provides insight into the E-field induced structural transformation. The stripe-like nanodomains in the unpoled system transformed into lamellar tetragonal domains with a reduced degree of displacement disorder during poling. It is proposed that the synergic effect of change in octahedral tilt disorder and cation displacement disorder leads to this transformation under an E-field. The criterion for achieving superior functional response includes stabilization of the long range order and reduction in the tilt disorder through compositional adjustments. Understanding of the poling mechanism in lead-free piezoelectric materials has been mostly limited to the behavior of domains under an applied field. However, this work provides an in-depth understanding of the changes in the local structure along with domain morphology under an applied field.