RAMAN-STUDY OF SINGLE-CRYSTAL ANATASE TIO2 UP TO 70 GPA

A single crystal of anatase TiO2 was studied by Raman spectroscopy at quasi-hydrostatic pressures up to 70 GPa. The crystallinity of the sample shortens the pressure range of the transition to an alpha-PbO2 structure to between 4.5 and 7 GPa. The resulting polycrystalline sample then transforms to a baddeleyite structure between 13 and 17 GPa. The Raman spectrum of this phase undergoes substantial changes in line intensities above 60 GPa, possibly due to a transition to a higher symmetry and coordination structure. Preliminary X-ray data at higher pressures also show the appearance of a new reflection, confirming the existence of a new phase.