Raman spectroscopy and phase transition of anatase TiO2 under high pressure

The behavior of anatase TiO2 single crystal under hydrostatic high pressure of up to 6.7 GPa has been investigated using a diamond anvil cell at room temperature by Raman spectroscopy. A pressure-induced and irreversible phas e transition occurs in the pressure range from 4.3 to 4.6 GPa. The pressure dependence of the Raman active modes of anatase was measured. The decrease in nu (5) band-frequency from 197 cm(-1) was observed. Some single crystal s of anatase were transformed to the high-pressure phase while retaining it s transparency and hardness. A mechanism for the transition of anatase to t he high-pressure phase is proposed on the basis of structural chemistry. (C ) 2001 Elsevier Science Ltd. All rights reserved.