Raman study of anatase (TiO2) at high pressure

The Raman spectra of anatase have been investigated under pressure up to 17 GPa and at room temperature. The pressure dependences of the Raman active modes are reported. A pressure-induced phase transition of anatase is observed at pressure above 7.1 GPa in the hydrostatic environment using a 4 :1 mixture of methanol and ethanol as pressure medium. On the basis of in situ powder X-ray diffraction data and comparison of the Raman spectrum of the high-pressure modification with that of TiO2, -II (a-PbO2, -type structure), it is evident that at high pressure anatase transforms irreversibly to Ti PbO2, -II.