Preparation of CeSiO₄ from aqueous precursors under soft hydrothermal conditions

Even though CeSiO₄ was synthesized one time through a hydrothermal treatment, the conditions leading to its formation remain largely unknown. In order to define the optimized conditions of synthesis, a multiparametric study was developed by varying the pH of the solution, the temperature, and the nature of the reactants and of the complexing ions in solution. This study highlighted that CeSiO₄ could not be obtained starting from Ce(iv) reactants. An optimal set of conditions was defined to prepare single phase samples. Pure CeSiO₄ was obtained through a hydrothermal treatment at 150 °C using a starting mixture of 1 mol L^-1 Ce(iii) nitrate and Na₂SiO₃ solutions and by adjusting the initial pH to 8. The chemical limitations observed during the synthesis of CeSiO₄ suggested that the formation of this phase may result from the slow in situ oxidation of a Ce(iii) silicate complex during the hydrothermal treatment.