Browsing by Author "Deschanels, X"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Phase separation in fluorite-related U 1– y Ce y O 2– x : new insights via variable temperature neutron diffraction
    (CEA, 2024-09-01) Simeone, D; Deschanels, X; Garcia, P; Avdeev, M; Ablott, TA; Thorogood, GJ
    The phase separation in the U1-yCey O2-x system for values of y between approximately 0.34 and 0.5 observed at low temperatures (below circa 600 K) purportedly involves only fluorite structures [1,3]. Therefore, to confirm this assumption it is logical to employ high resolution diffraction techniques that can track the progression of the oxygen-sub lattice and resolve peaks that may be overlapping. In this study, the phase separation in the U0.54Ce0.46O2-x system has been revisited using variable temperature high resolution neutron diffraction on samples that are sealed under Ar to prevent a change in oxidation state when heated. As neutron scattering lengths for Unat and O do not differ to a large degree, U coherent cross section 8.903 barn vs O coherent cross section 4.232 barn, information about the oxygen sub lattice can be obtained from neutron diffraction patterns. This is not the case for X-ray diffraction which has been used for the bulk of the studies on this system. Below a critical temperature, the existence of two fluorite related structures in the miscibility gap is confirmed: a stoichiometric U0.54Ce0.46O2 phase and an oxygen-deficient U0.54Ce0.46O2-x phase. Although the former is indeed a fluorite, we show that the other end-member phase has a C-type bixbyite structure, Figure 1. © The Authors