Is electrostrain >1% in oxygen deficient Na0.5Bi0.5TiO3 a composition effect?

For over two decades Na0.5Bi0.5TiO3 (NBT) -based lead-free piezoelectrics have attracted attention due to its ability to exhibit large electric-field driven strain. Compared to the popular Pb(Zr, Ti)O3 (PZT)-based piezoelectrics, which exhibit electrostrain of about 0.3%, the derivatives of NBT-based lead-free piezoelectrics at the ergodic-non ergodic relaxor crossover exhibit larger electric-field driven strain.0.45%. In recent years, there has been a concerted effort to increase the maximum electrostrain in lead-free piezoceramics. Recent reports suggest that oxygen deficient NBT- based piezoceramics can exhibit electrostrain.1%. In this paper we explore this phenomenon and show that the ultra high electric field driven strain measured is primarily a consequence of reducing the thickness of the disc dimension below 500 microns and not an exclusive effect of the composition.