Structure evolution of Bi4O7 under high pressure

X-ray diffraction and Raman spectroscopy measurements were used to study the structure evolution of Bi4O7 during compression. Two isostructural phase transitions were observed under high pressure, with the first transition to phase II occurring at approximately 3.0 (2) GPa and the second to phase III occurring at approximately 13.0 (5) GPa. The pressure-volume (P-V) curve was found to be discontinuous at those two pressure transition boundaries. By fitting the P-V curves in three different stages, the bulk moduli were estimated to be approximately 101 (2), 68 (2) and 172 (3) GPa. Such large differences in the bulk moduli confirm two isostructural phase changes in the three stages. An irreversible amorphization process was found to start at approximately 20 (1) GPa, and the sample gradually becomes fully amorphous during compression at 30 (1) GPa.

Automated summary

X-ray diffraction and Raman spectroscopy were used to study the structure evolution of Bi4O7 during compression. Two isostructural phase transitions were observed at approximately 3.0 GPa (transition to phase II) and 13.0 GPa (transition to phase III). The pressure-volume curve was discontinuous at these two pressure transition boundaries. The bulk moduli were estimated to be approximately 101 GPa, 68 GPa, and 172 GPa, indicating significant differences and confirming the two isostructural phase changes. An irreversible amorphization process started at approximately 20 GPa, resulting in complete amorphization at 30 GPa.