Xiaozhi Yan [HPSTAR Student]

Time: 14:00-15:00, April 2, 2014

Place: HPSTAR Meeting Room (Shanghai)

Title: Size-Dependent Pressure-Induced Phase Transformation and  Compressibility in Nanocrystalline Ho2O3

Abstract:

We studied the phase transitions and compressibility of Ho2O3 anocrystals using high-pressure synchrotron x-ray diffraction and Raman spectroscopy techniques. The onset transition pressure for nanocrystalline Ho2O3 from cubic to monoclinic is 14.7 GPa, which is about 6 GPa higher than that of bulk Ho2O3. The Ho2O3 nanocrystals did not transformed to hexagonal phase just like bulk Ho2O3, but to amorphous state irreversibly under higher pressure. The bulk modulus of cubic Ho2O3 nanocrystals was 186.4 GPa, which is about 10% lower than that of bulk Ho2O3. It is also observed that the bulk modulus determined using the apparent lattice parameters is much lower at the smaller diffraction vector Q than that at the larger Q values. These findings support the general model of a nanocrystal with expanded softer surface layer.