Synthesis of Lanthanides Doped CaTiO₃ Powder by the Combustion Process

Lanthanides such as La, Gd and Ce have recognized as elements of high level radioactive wastes immobilized by forming solid solution with CaTiO₃. For easy forming solid solution between CaTiO₃ and lanthanides, the combustion synthesis process was applied and the powder characteristics and sinterability were investigated. The proper selection of the type and the composition of fuels are important to get the crystalline solid solution of CaTiO₃ and lanthanides. When glycine or the mixtures of urea and citric acid with stoichiometric composition was used as a fuel, the solid solution of CaTiO₃ with La₂O₃ or Gd₂O₃ or CeO₂ was produced very well by the combustion process. The combustion synthesized powder seemed to have a good sinterability with the linear shrinkage of more than 25% up to 1500℃, while that of the solid state reacted powder was less than 10% at the same condition.