Local Variations of the Stress‐Modulated Antiferroelectric‐Ferroelectric Phase Transitions in Polycrystalline NaNbO ₃ Imaged with Raman Spectroscopy

Due to the growing significance of energy storage, ceramics for high energy density capacitors have become an increasingly prominent area of research. For this reason, current research primarily focuses on enhancing the energy storage performance and efficiency. Despite the importance for implementation in applications, however, there remain few investigations on the mechanical properties. Here, it is investigated the role of uniaxial compressive stress on polycrystalline NaNbO 3 , a lead‐free antiferroelectric with significant potential for advanced energy storage applications. Through ex situ stress‐dependent crystal structure analysis using XRD as well as Raman mapping, it is demonstrated that NaNbO 3 ceramics, which initially exhibit an antiferroelectric P phase accompanied by a ferroelectric Q phase, undergo a stress‐modulated change in the crystal structure and domain state. This is analogous to the well‐known irreversible electric field‐induced AFE‐to‐FE phase transition found in NaNbO 3 . Ex situ Raman mapping of unpoled and mechanically loaded samples revealed spatial variations in the AFE and FE phases, demonstrating the inhomogeneity of the stress‐modulated structural phase transition in the polycrystalline microstructure. In addition, the large signal mechanical response of poled and unpoled samples is characterized, showing a significant decrease in the coercive stress of NaNbO 3 and an increase in the backswitching rate due to the formation of a long‐range ordered ferroelectric structure with orientation and non‐180° domain switching. Revealing the complicated role of compressive stress on NaNbO 3 will help to understand real‐world operating conditions and provide deeper insights into the underlying physical mechanisms, providing guidance for the design and application of antiferroelectric materials.