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The Raman spectra of Bi2Ti4O11at non-hydrostatic pressure and Bi2Ti3.8Te0.2O11at hydrostatic pressure as well as at high temperature reveal that the soft mode phase transition in Bi2Ti4O11can be connected with the unstable Bi3+ion displacement.

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.