Morphology dependent sintering path of nanocrystalline ThO2

Thorium is most commonly precipitated as oxalate, because of the high efficiency regardless of precipitation conditions. Thorium oxalate readily decomposes into fine-grained ThO2 during heating, but keeps the macrostructure of the oxalate platelets. To assess the effects of precipitate macrostructure on the sintering behavior, different platelet morphologies were prepared and sintered. There are two factors which influence the sintering: the presence of holes within the platelets and the size of the platelets. Small platelets or precipitates with holes generally sinter to thorium dioxide pellets of a higher density and smaller grain size.