Size-dependent phase transition of Er2O3 under high pressure

The size effect on the structural and optical properties of cubic Er2O3 was investigated under pressure by in-situ angular dispersive synchrotron x-ray diffraction (AD-XRD), Raman scattering, photoluminescence (PL), and impedance spectroscopy. Contrary to the phase transition sequence of cubic→monoclinic→hexagonal in bulk Er2O3, a transformation from cubic directly to hexagonal was observed in Er2O3 nanoparticals. Compared with bulk Er2O3, nano-Er2O3 showed an obvious elevation of phase transition pressure and larger bulk module. A third-order Birch-Murnaghan fitting yields zero pressure bulk moduli (B0) of 181(5), and 226(4) GPa and their pressure derivatives (B′0) of 4.0(7), 1.9(5) for the cubic and hexagonal phases, respectively. The multiple PL lines of 4S3/2→4I15/2 originating from the cubic phase are also altered due to phase transformation. The impedance spectroscopy indicated that the nano-Er2O3 is an insulator up to 30 GPa. These findings give a fresh understanding of size influence on the phase ...