Pressure-Induced Phase Transition and Octahedral Tilt System Change of Ba\u3csub\u3e2\u3c/sub\u3eBiSbO\u3csub\u3e6\u3c/sub\u3e

High-resolution X-ray synchrotron powder diffraction studies under high-pressure conditions are reported for the ordered double perovskite Ba2BiSbO6. Near 4 GPa, the oxide undergoes a pressure-induced phase transition. The symmetry of the material changes during the phase transition from space group R3¯ to space group I2/m, which is consistent with a change in the octahedral tilting distortion from an a−a−a− type to a0b−b− type using the Glazer notation. A fit of the volume–pressure data using the Birch–Murnagaham equation of stateyielded a bulk modulus of 144(8) GPa for the rhombohedral phase