Multiparametric Study of the Synthesis of ThSiO₄ under Hydrothermal Conditions

A multiparametric study of the hydrothermal synthesis of ThSiO₄, thorite, was performed with the aim of determining the most efficient conditions to form single-phase samples. Among the experimental parameters examined, significant effects were found for the concentration of reactants in the starting mixture, pH of the reactive media, and temperature of the hydrothermal process. Such parameters affected both the rate of formation of thorite and the morphology of the final products synthesized. Precipitation of pure ThSiO₄ was obtained over a wide range of pH on going from C_HNO3 = 0.3 mol L^-1 to pH 9.1 with a yield of over 95%. Temperatures higher than 160 °C favor the formation of thorite. Finally, thorium and silicon concentrations above 2.1 × 10^-3 mol L^-1 are required to obtain pure thorium silicate.