CRYSTAL GRAIN-GROWTH DURING PHASE-TRANSFORMATION IN CERIUM METAL AT HIGH-PRESSURE

Crystal structures and orientation effects in cerium (Ce) metal were i nvestigated in the pressure range of 0-28 GPa by high-resolution synch rotron x-ray diffraction using image plate technique with a diamond-an vil cell. We observe crystal grain growth during the phase transformat ions to a-uranium structure both during compression and decompression cycle. We offer explanation for the long-standing controversy on the i ntermediate phases and attribute various crystal structure proposals t o low-resolution and orientation effects. This crystal grain growth du ring phase transformation in Ce at high pressure and ambient temperatu re is an unusual phenomenon among metals.