Simultaneous aluminium-26 and oxygen-18 transport in an alumosilicate glass

Simultaneous 26Al and 18O tracer diffusion experiments were performed in an alumosilicate glass (60 mol% SiO2, 10 mol% CaO, 10 mol% Na2O, and 20 mol% Al2O3). For the determination of the Al diffusion a novel technique was used, insofar as the isotope 26Al (half-life 7.4 × 105 years) was not used as a radioactive but as a quasi-stable tracer. Combined with a SIMS measurement the tracer concentration profiles could be obtained. At 800 °C DAl = 2.7 × 10-21 m2/s and DO = 3.4 × 10− 19 m2/s resulted. This observed difference in mobility is presumably related to the dissimilar roles the constituents Al and O play in the glass structure.