Uranium Oxide Phase Equilibrium Systems: III, UO ₂ –ZrO ₂

Abstract

The UO 2 –ZrO 2 phase equilibrium system contained no new compounds but was found to contain extensive solid solution. The UO 2 solid solution was cubic and extended up to 52 mole % ZrO 2 . Its lattice parameter varied from 5.46 to 5.32 a.u. with an increasing percentage of ZrO 2 . The zirconia solid solution when examined by quenching techniques was tetragonal and extended from 53 to 100% ZrO 2 . There were some indications that ZrO 2 transformed to a polymorphic form other than monoclinic or tetragonal at approximately 1900°C.