In situ high-pressure synchrotron X-ray diffraction study of the structural stability in NdVO₄ and LaVO₄

Highlights: • NdVO₄ and LaVO₄ were studied under high pressure using synchrotron powder XRD. • Both compounds exhibit first-order phase transitions. • In NdVO₄ the transition involves a symmetry breaking and in LaVO₄ is isomorphic. • The crystal structures of the high-pressure phases are assigned. • Axial and bulk compressibilities are determined. - Abstract: Room-temperature angle-dispersive X-ray diffraction measurements on zircon-type NdVO₄ and monazite-type LaVO₄ were performed in a diamond-anvil cell up to 12 GPa. In NdVO₄, we found evidence for a non-reversible pressure-induced structural phase transition from zircon to a monazite-type structure at 6.5 GPa. Monazite-type LaVO₄ also exhibits a phase transition but at 8.6 GPa. In this case the transition is reversible and isomorphic. In both compounds the pressure induced transitions involve a large volume collapse. Finally, the equations of state and axial compressibilities for the low-pressure phases are also determined