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 mater ial for the immobilization of radioactive waste from nuclear power rea ctors, has been prepared using coprecipitation, sol-gel, and solution combustion methods. All these processes initially yielded amorphous po wders, which on further calcination, crystallized to yield sphene alon g with perovskite, titania, and cristobalite. The coprecipitation-deri ved powder calcined at 1000 degrees C for 2 h showed the formation of single phase sphene; whereas, the sol-gel-derived and combustion-deriv ed powders required higher temperature (1200 degrees C for 2 h) for si ngle phase sphene to form. Coprecipitation-derived sphene powder achie ved 96% theoretical density when sintered at 1300 degrees C for 2 h, a nd the microstructure of the sintered body showed a uniform grain size of approximate to 1 mu m. (C) 1998 Elsevier Science Ltd.