X-ray diffraction studies of Sr3Cr2O8 and Ba3Cr2O8 at high pressures

The chromates Sr3Cr2O8 and Ba3Cr2O8 have been investigated by in situ synchrotron angle-dispersive X-ray diffraction in diamond anvil cells at room temperature up to 27.6 and 26.0 GPa, respectively. A phase transition of Sr3Cr2O8 was observed at 21.9 GPa and room temperature, and no phase change occurred for Ba3Cr2O8 up to 26.0 GPa in this study. The P–V data was fitted by the second-order Birch–Murnaghan equation of state, and the isothermal bulk modulus B0 was obtained as 97.0±1.3 GPa and 89.7±2.7 GPa for Sr3Cr2O8 and Ba3Cr2O8, respectively. The structural anisotropy increases with pressure increasing, and the a-axis is more compressible than the c-axis for both compounds.