In situ phonon dynamics decoding of the reversibility modulation in field-induced phase transitions of NaNbO 3 -based system via La 3 + doping

Sodium niobate (NaNbO₃, NN), as a rare room-temperature antiferroelectric material, exhibits significant applications in important fields such as pulse energy storage and multistate nonvolatile memories. However, pristine NN generally suffers from an irreversible field-induced phase transition, which prevents the observation of the characteristic double hysteresis loops of antiferroelectrics. Previous findings have revealed that its unstable antiferroelectric structure is strongly correlated with the occupancy instability of Na⁺ ions under external fields. Na_1-3xLaₓNbO₃ system is constructed in this work via doping the Na site with La³⁺, which differs obviously from Na⁺ in both mass and electronic structure. This strategy aims to realize a progressive evolution from irreversible to reversible phase transition under electric fields, by controlling the doping concentration of La³⁺. Based on the precise identification of Raman spectroscopy for phonon vibrations, the in situ Raman spectra under varying electric field and temperature are measured to conduct a detailed insight into the evolution pathways of multiple crucial phonons in samples. Accordingly, the modulation of La³⁺ on the reversibility of field-induced phase transition could be effectively deciphered. This work reinterprets the unique field-induced phase transition in NN-based materials from the perspective of phonon evolution, which lays an important research foundation for the design and development of NN-based devices with multiple transitions between different electrical ordering states.