Electric-field-induced phase transition in textured Bi0.5Na0.5TiO3-based thin films

The reversible electric-field-induced transition from ergodic relaxors to ferroelectric phase is a highly desirable feature for enhancing the functionality of (Bi,Na)TiO3 (BNT)-based materials. However, in oriented films, substrate-induced strain can significantly affect electric-field-induced structural transformations. The mechanistic interplay between strain and phase transition—crucial for real-world device applications—remains inadequately understood and represents a significant gap in the current understanding of ferroelectric materials. In this study, the electric-field-driven relaxor-to-ferroelectric transition is systematically investigated in textured BNT-based ergodic relaxor thin films. The transition is found to occur within a narrow range of applied electric fields, characterized by double-S-shaped polarization–electric-field (P–E) loops accompanied by four distinct current peaks at relatively low fields. As the electric field increases, ferroelectric behavior becomes dominant. Moreover, (001) texturing not only reduces the required driving electric field for the phase transition but also enhances the ferroelectric performance while suppressing frequency dispersion. These results offer important insights into the unique phase transition mechanisms of ergodic relaxor thin films and suggest potential pathways for optimizing their functional properties.