High-Pressure X‑ray Diffraction Investigation of Fe_0.9Al_0.1VO₄

This study demonstrates that the influence of cationic composition on the phase behavior of vanadates under high pressure must be meticulously considered. In this investigation, we report an in situ high-pressure powder X-ray diffraction investigation on triclinic Fe_0.9Al_0.1VO₄ (space group P1̅) up to 11 GPa. The structural sequence of Fe_0.9Al_0.1VO₄ is different than that of FeVO₄. Our analysis shows that Fe_0.9Al_0.1VO₄ undergoes a first-order structural phase transition at 2.85 GPa to another triclinic structure described by the same space group with a volume collapse of ∼9%. At 6.1 GPa, we observed the onset of a second phase transition to a monoclinic structure (space group P2/c), with coexistence of both phases until 8.55 GPa. The transformation to the second phase is completed at 9.15 GPa, with a volume collapse of ∼13%. On release of pressure to ambient conditions, we have observed the coexistence of the second and first high-pressure phases. The compressibility of the three phases of the compound has been studied too. We have observed variations in structural sequence and compressibility behavior due to Al incorporation. Since electronic properties could be modified by tuning the crystal structure, the present results could have an impact on applications of the studied compound such as photocatalysis and batteries.