In situ studies of the decomposition of ammonium uranyl carbonate in an electron microscope

An electron microscope has been used to study the reduction of ammonium uranyl carbonate (AUC) to UO₂. The reactions could be followed both in the diffraction and the lattice image mode. The first intermediate obtained was amorphous UO₃. Depending on the experimental conditions, either crystalline UO₂ was formed directly from this phase, or several other intermediates were indicated.Properties like crystallinity and crystallite size of final UO₂ were found to be a function of experimental conditions. Comparisons with properties of UO₂ from the industrial process have been made.