Oxygen-18, aluminium-26 and silicon-30 self diffusion in aluminosilicate glasses
18O, 26Al, and 30Si tracer diffusion in model aluminosilicate glasses with varying Al3+/Na+ ratios was investigated using secondary ion mass spectrometry (SIMS) depth profiling. For aluminium tracer diffusion measurement the long-lived radioactive isotope 26 Al served as a pseudo-stable isotope (half-life 7·4×105 years). The tracer diffusion measurements above the glass transition (T g) at temperatures from 490 to 821°C clearly show that the mobility of aluminium is about two orders of magnitude lower than that of oxygen in the considered aluminosilicate glasses. The mobility of silicon is a further order of magnitude lower. The activation enthalpy of diffusion is largest for silicon, followed by aluminium and is lowest for oxygen. For both oxygen and aluminium the mobility decreases (and the activation enthalpy increases) with increasing Al3+/Na+ ratio. For the glass with the highest Al3+/Na+ ratio the tracer diffusivities of 18O and 26Al were also measured below T g. Possible diffusion mechanisms are discussed for all three elements.
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Document Type: Research Article
Publication date: February 1, 2013