  Room temperature angle-dispersive x-ray diffraction measurements on
zircon-type TbVO4 and CeVO4 were performed in a diamond-anvil cell up to 50 GPa
using neon as pressure-transmitting medium. In TbVO4 we found at 6.4 GPa
evidence of a non-reversible pressure-induced structural phase transition from
zircon to a scheelite-type structure. A second transition to an
M-fergusonite-type structure was found at 33.9 GPa, which is reversible.
Zircon-type CeVO4 exhibits two pressure-induced transitions. First an
irreversible transition to a monazite-type structure at 5.6 GPa and second at
14.7 GPa a reversible transition to an orthorhombic structure. No additional
phase transitions or evidences of chemical decomposition are found in the
experiments. The equations of state and axial compressibility for the different
phases are also determined. Finally, the sequence of structural transitions and
the compressibilities are discussed in comparison with other orhtovanadates and
the influence of non-hydrostaticity commented.
