Synthesis, Properties, Sintering and Microstructure of Sphene, CaTiSiO5: A comparative Study of Coprecipitation, Sol-Gel and Combustion Processes

Sphene (CaTiSiO5), a titanosilicate ceramic considered as a host material for the immobilization of radioactive waste from nuclear power reactors, has been prepared using coprecipitation, sol-gel, and solution combustion methods. All these processes initially yielded amorphous powders, which on further calcination, crystallized to yield sphene along with perovskite, titania, and cristobalite. The coprecipitation-derived powder calcined at 1000°C for 2 h showed the formation of single phase sphene; whereas, the sol-gel-derived and combustion-derived powders required higher temperature (1200°C for 2 h) for single phase sphene to form. Coprecipitation-derived sphene powder achieved 96% theoretical density when sintered at 1300°C for 2 h, and the microstructure of the sintered body showed a uniform grain size of ≈1 μm.