Discovery of a new weberite-type antiferroelectric: La3NbO7

Abstract

Antiferroelectrics are antipolar materials which possess an electric field-induced phase transition to a polar, ferroelectric phase and offer significant potential for sensing/actuation and energy-storage applications. Known antiferroelectrics are relatively scarce and mainly based on a limited set of perovskite materials and their alloys (e.g., PbZrO$_3$, AgNbO$_3$, NaNbO$_3$). Here, a new family of lead-free, weberite-type antiferroelectrics, identified through a large-scale, first-principles computational search is introduced. The screening methodology, which connects lattice dynamics to antipolar distortions, predicted that La$_3$NbO$_7$ could exhibit antiferroelectricity. We confirm the prediction through the synthesis and characterization of epitaxial La$_3$NbO$_7$ thin films, which display the signature double hysteresis loops of an antiferroelectric material as well as clear evidence of an antipolar ground state structure from transmission electron microscopy. The antiferroelectricity in La$_3$NbO$_7$ is simpler than most known antiferroelectrics and can be explained by a Kittel-type mechanism involving the movement of niobium atoms in an oxygen octahedron through a single phonon mode which results in a smaller change in the volume during the field-induced phase transition. Additionally, it is found that La$_3$NbO$_7$ combines a high threshold field with a high breakdown field ($\approx$ 6MV/cm) - which opens up opportunities for energy-storage applications. This new weberite-type family of materials offers many opportunities to tune electrical and temperature response especially through substitutions on the rare-earth site. Ultimately, this work demonstrates a successful data-driven theory-to-experiment discovery of an entirely new family of antiferroelectrics and provides a blueprint for the future design of ferroic materials.