Oxygen-18 tracer diffusion in a crystallised lithium-aluminosilicate glass

In this work we present first O-18 tracer diffusion data in a crystallized LAS4 glass. The glass of LAS4 composition (close to Li2O center dot Al2O3 center dot 4SiO(2)) is free of nucleating agents and has a very low tendency to nucleate crystals in the volume. A thin ZrTiO4 layer (similar to 70 nm thick) was deposited by argon ion beam sputtering and served to preferentially nucleate high-quartz solid solution crystallites from the surface. All samples crystallised at the very early stage of the respective diffusion annealing time, i.e. virtually before the onset of the O-18 tracer diffusion. The microstructure of the crystallised LAS glass is composed of crystalline domains (high-quartz solid solutions and keatite solid solutions) and a glassy phase of low viscosity in the domain boundaries. The oxygen transport occurs predominantly in the glassy phase of the domain boundaries and is faster than the transport of network forming cations or larger configurations in the glassy phase.