Raman spectroscopic study of the pressure-induced phase transition in TiO 2

Abstract

Pressure dependence of Raman spectra in TiO 2 was measured up to 40 GPa using diamondanvil cell at room temperature. Two phase transitions were observed with increasing pressure. Rutile phase begins to transform into α-PbO 2 phase at about 10 GPa and the α-PbO 2 phase coexists with rutile phase up to 15 GPa. The α-PbO 2 phase disappears above 15 GPa and single phase of different structure is observed at 20 GPa. This new high-pressure phase is stable up to 40 GPa. Comparing the Raman spectra of the new high-pressure phase of TiO 2 measured at 20 GPa with those of ZrO 2 and HfO 2, the crystal structure of the high-pressure phase has been determined as the baddeleyite structure. The line widening of Raman band observed for the high-pressure phase is explained by the disorder in oxygen ion site predicted from the proposed mechanism for the pressure-induced phase transition in TiO 2.