The Local-Scale Origin of Ferroic Properties in BiVO<sub>4</sub>
Bryce G. Mullens, Frederick P. Marlton, Helen E. A. Brand, Helen E. Maynard‐Casely, Michelle Everett, Matthew G. Tucker, Emily R. Van Auken, Alicia Manjón‐Sanz, Gianguido Baldinozzi, Simon M. Vornholt, Karena W. Chapman, Brendan J. Kennedy
Abstract
Earth-abundant metal oxides are excellent candidates for photocatalytic applications due to their low cost and high stability in aqueous solutions. Materials that contain a combination of metal cations with an s 2 electron lone pair and a d 0 electronic configuration, such as BiVO 4, possess favorable band gaps. BiVO 4 has also been reported to possess noncentrosymmetric polar properties, such as flexoelectricity, piezo-photocatalysis, and an anomalous photovoltaic effect, despite its centrosymmetric crystal structure. Here, it is shown how centrosymmetric materials possessing s 2 and d 0 cations can display “hidden” local-scale features, often ignored by conventional crystallography, that influence their physical properties. Anomalous peak shapes are observed in the high-resolution synchrotron X-ray powder diffraction of BiVO 4, and temperature-dependent local-scale distortions are revealed using neutron total scattering methods. Together, these suggest the polar properties of BiVO 4 are related to local-scale distortions induced by the Bi 3+ 6 s 2 electron lone pairs. This demonstrates the possibility of engineering specific interatomic distances between lone pair-bearing cations and the anion sublattice, creating new opportunities for photocatalytic and polar materials from compounds with long-range centrosymmetric structures.