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 α-PbO2 structure at 2.6–4.5 GPa, we found that the nano-anatase phase remains stable to pressures as high as ∼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-α-PbO2 phase transformation (2.6–4.5 GPa in bulk anatase), and then leads to the amorphization of nano-anatase under strong compression.