Pressure-induced structural transformations and new polymorphs in BiVO4

Abstract

BiVO₄ has attracted much attention in recent years due to its active photocatalytic and microwave dielectric properties. BiVO₄ exhibits a rich structural polymorphism, and its properties strongly depend on the crystalline phase. Therefore, it is of great importance to achieve an easy control of its crystalline phase. In the present work, phase stability and vibrational properties of fergusonite- and zircon-type BiVO₄ are investigated up to 41.6 GPa by in situ synchrotron X-ray diffraction (XRD), Raman spectroscopy, and first principles calculation. Upon compression, although having different initial structures, both types of BiVO₄ consecutively transform to scheelite- and β-fergusonite structures. For the first time reported for BiVO₄, the β-fergusonite structure is determined using first principles computational techniques and from refinement of the XRD data. Along the way, one new phase of BiVO₄ is theoretically predicted at higher pressures. Moreover, both the fergusonite-to-scheelite and scheelite-to-β-fergusonite transitions are reversible, while the zircon-to-scheelite transition is irreversible. A large volume collapse is observed associated with each phase transition, and the equations of state for different types of BiVO₄ have been determined. These results provide new insights into the relationship between different structural types in the AVO₄ family.