High-pressure structural investigation of several zircon-type orthovanadates

Abstract

Room temperature angle-dispersive x-ray diffraction measurements on zircon-type ${\text{EuVO}}_{4}$, ${\text{LuVO}}_{4}$, and ${\text{ScVO}}_{4}$ were performed up to 27 GPa. In all the three compounds we found evidence of a pressure-induced structural phase transformation from zircon to a scheelite-type structure. The onset of the transition is near 8 GPa, but the transition is sluggish and low-pressure and high-pressure phases coexist in a pressure range of about 10 GPa. In ${\text{EuVO}}_{4}$ and ${\text{LuVO}}_{4}$ a second transition to a $M$-fergusonite-type phase was found near 21 GPa. The equations of state for the zircon and scheelite phases are also determined. Among the three studied compounds, we found that ${\text{ScVO}}_{4}$ is less compressible than ${\text{EuVO}}_{4}$ and ${\text{LuVO}}_{4}$, being the most incompressible orthovanadate studied to date. The sequence of structural transitions and compressibilities are discussed in comparison with other zircon-type oxides.