Pressure induced phase transformation in U2O(PO4)2

The high pressure behavior of U2O(PO4)2 has been investigated with the help of Raman scattering and X-ray diffraction measurements up to ∼14 and 6.5 GPa, respectively. The observed changes in the Raman spectra as well as the X-ray diffraction patterns suggest that U2O(PO4)2 undergoes a phase transition at ∼6 GPa to a mixture of a disordered ambient pressure phase and a new high pressure phase. The new phase resembles the triclinic mixed-valence phase of uranium orthophosphate (U(UO2)(PO4)2). On release of pressure the initial phase is not retrieved.