Room-Temperature Ferroelectric-Antiferroelectric Transitions in NaNbO₃ Materials

The recent development of dielectric phase transitions in solid-state materials reveals the main role of structural phase transitions, which generate new properties emerging by external stimulation. In this context, the present study aimed to investigate structural, morphological, dielectric, and electric characteristics of sodium niobate NaNbO₃, prepared by solid-state reaction. X-ray powder diffraction results exhibited that this material crystallizes in an orthorhombic perovskite structure, proving the existence of both Pbcm and P2₁ma space groups at room temperature. Furthermore, a microstructural investigation, based on scanning electron microscopy, showed multigrain agglomerations of about 600 nm consisting of fine crystallites with irregular shapes and sizes. Moreover, dielectric and electrical findings, obtained by wide-range impedance spectroscopy of frequencies [10²-10⁶ Hz] and temperatures [220-400 K], revealed the possibility of a FE-AFE dielectric phase transition accompanied by a P2₁ma-Pbcm structural phase transition at room temperature. Thus, the AC conductivity plots follow Jonscher's power law with thermal activation according to Arrhenius' law by 0.320 and 0.646 eV energies, probably attributed to the FE and AFE phases, respectively. Concerning charge carrier transport, it is demonstrated that the correlated barrier jump (CBH) model or the small polar tunnel model (NSPT) was considered to be the most appropriate to interpret the conduction mechanisms of the NaNbO₃ ceramic in the considered temperature range.