High-Pressure Metathesis Synthesis and Physical Property Characterization of Cubic Fluorite-Structured CeO2Cl0.07

The 4f electron of Ce have long attracted extensive attention due to their unique delocalization mechanism and their influence on atomic structure, phase transformation behavior, and magnetic structure. We synthesized CeO₂Cl_0.07 with a cubic fluorite structure by changing the chemical ratio of the precursors (CeCl₃, MgO powder) and regulating the high-pressure solid-state metathesis reaction (HSM) under the high temperature and high pressure conditions provided by a large volume press (1873 K, 5 GPa). We characterized the sample using diamond anvil cell (DAC), high-pressure in-situ synchrotron X-ray diffraction, scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), and high-pressure Raman spectroscopy. We obtained the P-V curve and compared it with CeO₂, finding that CeO₂Cl_0.07 is more compressible. We obtained the high-pressure Raman phonon spectrum (F_2g), and discovered that the relationship of CeO₂Cl_0.07 with pressure changes in the 0-2 GPa range and near 15 GPa also shows abnormality under non-hydrostatic pressure conditions. We believe that the doping of Cl elements introduces oxygen vacancies, which increases the concentration of Ce³⁺, thereby causing the delocalization of 4f electron and resulting in the observed phenomenon. This study developed a new high-pressure synthesis pathway for cerium-based compounds and revealed their behavior under high-pressure conditions.