XRD STUDY OF U_3O_8 STRUCTURE AT DIFFERENT TEMPERATURE

The structure change of triuranium octaoxide (U3O8) is studied by Xray diffraction in ambient atmosphere at temperature from 25 ℃ to 850 ℃.There are two kinds of phases of U3O8 in the temperature range are studied,and the transformation temperature is about 300 ℃.The lower temperature phase is orthorhombic with space group Amm2,and it changes to another phase with better symmetry around 300 ℃.Another phase,the higher temperature phase,is hexagonal with space group P62m,which is stable from 300 ℃ to 800 ℃.The lattice parameters of XRD peaks of U3O8 are also investigated at different temperature.It is found that they change with the temperature under rules.