Antiferroelectric twin domains and domain walls in K₃[Nb₃O₆(BO₃)₂]

Antiferroelectric materials exhibit an anti-polar alignment of electric dipoles, giving rise to intriguing physical properties and functional behaviors. For example, enabled by their characteristic electric-field response, antiferroelectrics facilitate particularly high energy densities, holding great potential for energy storage applications. Analogous to ferroelectrics, the responses of antiferroelectrics are closely linked to their domains, but their nanoscale structure and physics are much less explored.

In this work, we apply different scanning probe microscopy techniques to image and investigate the domains and domain walls in antiferroelectric K₃[Nb₃O₆(BO₃)₂]. Using piezoresponse force microscopy, we show that the antiferroelectric domains exhibit a pronounced piezoresponse, consistent with the non-centrosymmetric crystal structure. At the nanoscale, a chevron-like pattern of antiferroelectric twin domains develops, where the crystallographic structure changes by 120° across the domain walls. Interestingly, we observe the formation of positively and negatively charged antiferroelectric twin walls with distinctly different piezoelectric and electrostatic responses, arising from a small canted electric moment of the anti-polar order. Our findings provide new insight into the nanoscale physics of antiferroelectrics, revealing novel types of ferroic domain walls with unusual mechanical and electronic properties.