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

• 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.

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.

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