Phase stability and energy storage properties of polycrystalline antiferroelectric BaTiO3-substituted NaNbO3 thin films

Lead-free sodium niobate (NN) thin films with varying barium titanate (BT) content and 1 mol% manganese were deposited on platinized silicon substrates by chemical solution deposition. Microstructural analysis reveals a change in nucleation mechanism, and X-ray diffraction and Raman spectroscopy confirmed a composition-driven antiferroelectric (AFE) to ferroelectric (FE) phase transition (0.01 < x < 0.03), providing a stability interval for the AFE phase despite increasing the tolerance factor. The thin films show well-shaped ferroelectric response under applied electric field, indicating an irreversible field-induced phase transition. The composition with 7 mol% BaTiO3 showed the most promising energy storage properties (Wrec ~5.7 J/cm3 and 68% efficiency (η)), along with excellent thermal stability up to 120°C and largely improved cyclic stability up to 5*106 bipolar cycles. These findings highlight the potential of NN-based thin films as lead-free candidates for energy storage, emphasizing the importance of stabilizing the AFE phase under electric fields for practical applications.