Polar Topologies in Lead‐Free Oxide Antiferroelectric Ceramics

ABSTRACT

Polar topological structures have emerged as an important frontier in ferroic materials because of their unusual polarization textures and potential functionalities. However, their existence and formation mechanism in antiferroelectrics remain largely elusive owing to the intrinsic self‐compensating antipolar ordering. Here, diverse polar topologies are revealed in CaTiO ₃ ‐doped NaNbO ₃ antiferroelectric ceramics using atomic‐resolution integrated differential phase contrast scanning transmission electron microscopy. Continuous dipole rotation is directly observed at different domain walls, giving rise to topological vortex configurations at uncharged inclined 90° domain walls, antivortex configurations at charged inclined 90° domain walls, alternating vortex‐antivortex arrays at vertical 90° domain walls, and periodically arranged center‐convergent and center‐divergent polarization textures at charged 180° domain walls. Phase‐field simulations reveal that these topological structures originate from the diffusive superposition of different antipolar variants at domain walls, which is driven by the intrinsic competition between bulk and gradient energies. These results establish a direct relationship between domain walls, charge state, and polar topologies, and demonstrate that modulated antiferroelectrics provide a platform for exploring intrinsic polar topologies states and may open new avenues for optimizing dielectric energy‐storage performance and electromechanical responses in lead‐free antiferroelectric materials.