Effect of A-site non-stoichiometry in NaNbO3 ceramics

NaNbO₃ (NN) is a potentially promising material for energy storage and conversion. Understanding the structure-property relationships of NN is crucial for its precise development and implementation in various devices. This work reports the effect of Na non-stoichiometry on structure and ferroelectric properties of polycrystalline NN ceramics. Slight deviations of Na content in NN were observed to create large variations in microstructure, such as grain morphology and reduction in grain size. An insignificant phase change is observed in x-ray diffraction analysis; however, the pair distribution function (PDF) results show a nonuniform atomic displacement which are not directly observed by standard crystallographic techniques. A small amount of Na excess (2 mol.%) in NN enhanced the dielectric constant, polarization, and strain response, whereas a deficiency of same amount degrades electromechanical performance. This work not only explores Na non-stoichiometric effect in NN, but also provides a pathway for development of high performance NN-based ceramics.