Compressibility and phase transition of δ-UO3 under high pressure

A compressibility collapse transition of delta -UO3 (ReO3 structure type) was detected at 0.3 GPa and room temperature using X-ray diffraction in a diamond anvil cell. The compressibility of UO3 increased from 6.3X10(-1) to 9.3x10(-2) GPa(-1) at the transition point. The p-V relationship up to 2.2 GPa is presented. An amorphisation was observed at 2.2 GPa. The investigation of bulk amorphous samples obtained under high pressure at room temperature showed that the amorphisation is connected with the kinetics of the alpha -to-beta UO3 phase transformation. (C) 2001 Elsevier Science B.V. All rights reserved.