In situ X-ray diffraction study of phase transitions of FeTiO3 at high pressures and temperatures using a large-volume press and synchrotron radiation

摘要

The phase transformation from ilmenite to perovskite in FeTiO₃ was directly observed using synchrotron-based X-ray diffraction and a large-volume press. The perovskite phase is temperature quenchable at 20 GPa and converts into the LiNbO₃ phase at pressures below 15 GPa at room temperature. The LiNbO₃ phase transforms into the ilmenite phase at 10 GPa and 673 K. However, the back-transformation from the ilmenite to the LiNbO₃ phase was not observed, thus strongly suggesting that the LiNbO₃ phase is not thermodynamically stable but rather a retrogressive phase formed from perovskite during decompression at room temperature.