Synthesis and sintering of nanocrystalline thoria doped with CaO and MgO derived through oxalate-deagglomeration

Thorium dioxide doped with oxides of magnesium and calcium was prepared from deagglomerated mixed oxalates. The influence of the dopant oxide concentration (0.1, 0.25 and 0.5 mol% MO, M = Mg, Ca) on the powder properties was studied. The dependence of bulk density, specific surface area, X-ray crystallite size, residual carbon content and distribution of particle size on the dopant concentrations was investigated in detail. The transmission electron microscopy (TEM) investigations revealed that the powders comprised cuboidal agglomerates with a nanocrystalline substructure (10 nm). It was found that 0.5 mol% calcia doped thoria exhibits better sinterability than pure thoria and magnesia doped thoria at a temperature as low as 1673 K. Further, it was demonstrated for the first time that doping nanocrystalline thoria with calcia helps reduce the de-sintering phenomena.