Probing the modulation of internal stress field on phase transitions in sodium niobate by polarized Raman spectroscopy

Sodium niobate (NaNbO3, NN) serves as an ideal model system for investigating the origins of diverse electrical polarization behaviors owing to its rich polymorphism and complex phase transition sequences. Its intrinsic antiferroelectric character further exhibits significant potential for applications in pulsed power energy storage and multi-state non-volatile memory technologies. In particular, although the P and R phases in NN both display antiferroelectric ordering, they exhibit distinct superlattice behaviors. These structural differences give rise to intriguing physical phenomena during the phase transition process, thereby garnering significant research interest. Previous studies often attribute the complex phase evolution in NN to competitive interactions mediated by a minor Q phase component under internal stress fields. Furthermore, these investigations primarily treat the P phase as the dominant structure, which significantly hinders a thorough understanding of stress field effects on the P–R phase transition process. In this study, NN samples predominantly exhibiting the Q phase at room temperature were prepared through process tuning. Furthermore, by varying defect concentrations, a series of NN systems with graded internal stress gradients were constructed. Furthermore, leveraging the sensitive detection capability of polarized Raman spectroscopy for polarizability changes, we investigated the in situ evolution of various phonons under temperature-field conditions. The study explores the mechanisms of phonon synergistic contributions induced by stress gradients during the heating of NN from the P to the R phase. These findings provide an important research foundation for understanding antiferroelectric behavior evolution in NN and for developing high-performance NN-based antiferroelectric devices.