| Abstract
| - High-pressure behaviors of wurtzite-type hexagonal CoO nanocrystals were investigated by in situ high-pressure synchrotron radiation X-ray diffraction measurements up to 57.4 GPa at ambient temperature. It isfound that bulk modulus of the hexagonal CoO phase is about 115 GPa at zero pressure. During compression,the hexagonal CoO phase transfers into rocksalt-type cubic phase in the pressure range of 0.8−6.9 GPa. Thevolume collapse accompanied by the transition was estimated to be about 20%. This is irreversibly phasetransformation; that is, the cubic CoO phase remains after pressure release. Based on the data of peak widthvs pressure, a cubic-to-rhombohedral phase transition was detected for the nanocrystalline cubic CoO phasewith the transition pressure of about 36 GPa, lower than 43 GPa for bulk cubic CoO phase. The bulk modulusof the nanocrystalline cubic CoO phase of about 258 GPa is larger than 180 GPa for the corresponding bulkcubic CoO phase.
|
