Trapping of cubic ZnO nanocrystallites at ambient conditions

Dense powder of nanocrystalline ZnO has been recovered at ambient conditions in the metastable cubic structure after a heat treatment at high pressure (15 GPa and 550 K). Combined x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) experiments have been performed to probe both long-range order and local crystallographic structure of the recovered sample. Within uncertainty of these techniques (about 5%), all the crystallites are found to adopt the NaCl structure. From the analysis of XRD and XAS spectra, the cell volume per chemical formula unit is found to be 19.57(1) and 19.60(3) Angstrom(3), respectively, in very good agreement with the zero-pressure extrapolation of previously published high-pressure data. (C) 2002 American Institute of Physics.