Compressibility and phase transition of delta-UO3 under high pressure

A compressibility collapse transition of delta -UO3 (ReO3 structure type) w as detected at 0.3 GPa and room temperature using X-ray diffraction in a di amond 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 G Pa is presented. An amorphisation was observed at 2.2 GPa. The investigatio n of bulk amorphous samples obtained under high pressure at room temperatur e showed that the amorphisation is connected with the kinetics of the alpha -to-beta UO3 phase transformation. (C) 2001 Elsevier Science B.V. All righ ts reserved.