Emerging Phase Transitions in Lead-Free Antiferroelectric Thin Films

As one of the prominent lead-free antiferroelectric alternatives, NaNbO₃ has received considerable research attention owing to its significant potential in energy storage applications. It is also renowned for being one of the most structurally complicated perovskite materials, exhibiting a rich set of structural phases characterized by distinct symmetries, ferroic orders, and oxygen octahedral tilting patterns. This intricate energy landscape in NaNbO₃ also opens up possibilities for inducing novel phase transitions through various external stimuli. In this presentation, I will introduce our recent studies on the intrinsic size dependence of antiferroelectricity in freestanding NaNbO₃ membranes. Through a wide range of experimental and theoretical approaches, we probe an intriguing antiferroelectric-to-ferroelectric transition that occurs as the membrane thickness decreases. Additionally, I will present our recent findings regarding an intriguing strain-induced phase transition in NaNbO₃ films, where we observed the presence labyrinthine domain patterns that self-organize into topological polar domains. Our work demonstrates enormous potential of using NaNbO₃ as a fertile ground for exploring emerging phase transitions and phenomena.