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 (B-0) 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 S-4(3/2)-> I-4(15/2) 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 transition sequences and sheds light on the applications of nano-Er2O3. Published by AIP Publishing.