High-pressure structural transformations of PbCrO4 up to 51.2 GPa: An angle-dispersive synchrotron X-ray diffraction study

We report on high-pressure X-ray diffraction measurements up to 51.2 GPa in PbCrO4 at room temperature. Three high-pressure phases with structures different than the ambient-pressure monazite-type (P21/n) are reported. One phase transition was found at 3.8 GPa to an isomorphic structure to monazite. A second transition occurs at 11.1 GPa. After this transition, the coexistence of tetragonal (I41/a) and monoclinic (P21) structures is detected up to 21.1 GPa. Beyond this pressure and up to 51.2 GPa, only the high-pressure monoclinic phase is observed. Upon decompression all structural changes are reversible. Finally, the axial compressibilities for the different phases have been determined as well as the equations of state.