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. NaNbO₃ is also known 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 opens up possibilities for inducing and controlling novel phase transitions via strain, thickness, and electric field. 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 intriguing topological polar structures. Our work demonstrates enormous potential of using NaNbO₃ as a fertile ground for exploring emerging phase transitions and phenomena in the family of complex oxides.