Structural behavior of Sr2Bi2O5 at high pressures

The structure of Bi₂Sr₂O₅ at high pressures is investigated by in situ X-ray diffraction (XRD) and Raman scattering methods. Raman results indicate that there are two pressure-induced phase transitions that occurred at ∼1.4 and ∼11 GPa, respectively. XRD measurements reveal only one high-pressure phase, which is indexed with a monoclinic unit cell and the possible space groups are P121(No. 3), P1m1(No. 6) and P12/m1(No. 10). The phase transition above 11 GPa is probably due to the symmetry change without discontinuity of the unit cell. The high-pressure phase is quenchable and it is a new dense form and about 11% denser than the normal orthorhombic Bi₂Sr₂O₅ at room conditions.