Pressure transmitting medium-dependent structure stability of nanoanatase TiO2 under high pressure

The pressure transmitting medium (PTM)-dependent structure stability of ∼12 nm nanoanatase TiO2 under high pressure has been investigated using in situ synchrotron X-ray powder diffraction techniques at room temperature. We found that the starting anatase phase (I41/amd) transforms into the monoclinic baddeleyite phase (P21/c) regardless of embedded in PTM or not. However, the beginning and ending pressure for the transformation under quasihydrostatic compression is found to be ∼7 GPa higher than that of under nonhydrostatic compression, and amorphization of sample occurs more easily during the former condition. This result indicates that the interface energy between the PTM and nanoparticles undoubtedly modifies the phase stability during high pressure experiments.