Rutherford backscattering investigation of radiation damage effects on the leaching of sphene and sphene-based glass-ceramics

Ion implantation techniques, using markers of 2 to 6×1015/cm2 of 280 keV Bi ions, and Rutherford backscattering depth profile analysis have been used to study radiation effects on the short-term leaching behaviour in aqueous media of sphene (CaTiSiO5) and sphene-based glass-ceramics designed for the immobilization of radioactive waste. Such heavy ion implantation of sphene is sufficient to have metamictized the top ~ 1000 Å layer. Leaching in distilled water or a 4 mol/1 NaCl solution, led to surface depletion of Ca and Si and to enrichment of Ti, in agreement with previous reported measurements made by other techniques on unirradiated sphene. Average leach rates of the amorphized sphene decreased with time, reaching a steady-state value after ~ 48 h. As deduced from annealing experiments, radiation damage induced by the ion-implanted marker results in an increase in leach rate of as much as an order of magnitude. The results on the glass-ceramics were similar to those obtained on the sphene.