Size effect on the pressure-induced phase transition in Lu2O3

The impact of particle size on the pressure-induced phase transition of cubic Lu2O3, the heaviest rare earth sesquioxide (RE2O3), was examined through a collaborative experimental and theoretical investigation. The high-pressure in situ Raman measurements and ab initio theoretical calculations provide verification of the enhanced phase stability of the cubic phase from 17.3 to 27.3 GPa for bulk and nanosized Lu2O3, respectively. In comparison to the bulk Lu2O3, the cubic-monoclinic phase transition is suppressed in nano-sized Lu2O3. In contrast, the hexagonal Lu2O3 was observed to form directly from the cubic phase, with the absence of the intermediate monoclinic phase. The size-dependent structural instability and transition sequence are correlated with changes in the thermodynamics and kinetics of the phase transformations, which can be well explained by ab initio density functional theory (DFT) calculations. The surface energy of nano-sized Lu2O3 accounts for a large proportion of the total energy, which may play an important role in the selection of phase transition paths. These findings offer insights into the size effect on the phase transitions of RE2O3 and provide guidance for the fabrication of new RE2O3 materials with distinctive properties.