Neutron Diffraction study of feldspar glasses. Mixed alkali effect

Radial distribution function analysis was made using neutron diffraction on several glasses along the NaA1Si308-KA1Si308 (albite-orthoclase) join as well as on a natural obsidian sample. Comparison of the interference functions in reciprocaI space shows a non-linear increase of the width of the first sharp diffraction peak which indicates a decrease of the medium-range order (MRO) with increasing K20 content. The observed changes in the MRO were correlated with the non-linear variation of the bulk transition temperature, Tg, and might reflect a strong temperature dependence of the corresponding liquid structures