Raman spectroscopic study on pressure-induced amorphization in nanocrystalline anatase (TiO2)

A raman spectroscopic investigation was carried out to study the pressure-induced phase transformation in nanocrystalline anatase (TiO2) up to 37 GPa. As compared to a macrocrystalline solid which transforms to the alpha -PbO2 structure at 2.6-4.5 GPa, we found that the nano-anatase phase remains stable to pressures as high as similar to 24 GPa, and then transforms to an amorphous phase. The new amorphous phase is quenchable upon release of pressure to ambient condition. An increased surface energy may stabilize the nano-anatase, suppressing the appearance of anatase-to-alpha -PbO2 phase transformation (2.6-4.5 GPa in bulk anatase), and then leads to the amorphization of nano-anatase under strong compression. (C) 2001 Elsevier Science Ltd. All rights reserved.