Berlin 2008 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 9: Poster
DF 9.18: Poster
Dienstag, 26. Februar 2008, 15:00–18:00, Poster G
Effects of MoO3 and WO3 on phase separation of a soda-lime-silica glass — •Rainer Kranold1 and Armin Hoell2 — 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — 2Hahn-Meitner-Institut Berlin, D-14109 Berlin, Germany
The base glass, 13Na2O-11CaO-76SiO2, undergoes subliquidus phase separation. Below the binodal temperature, Tb, the glass separates into two amorphous phases, silica enriched droplets and a silica-poor matrix. The phase separation process is governed by two competitive parameters, the thermodynamic driving force, Δµ, and the interface tension, σ. Here, the effects of small MoO3 and WO3 additions to the base glass on the parameters Δµ and σ are investigated. By determination of the wetting angle of a drop of the liquid glass melt on the flat surface of pure silica glass it was found that additions of MoO3 or WO3 to the base glass increase the value of σ. The growth process of the droplets at 600 ∘C in glasses with and without MoO3 or WO3 was studied by small-angle X-ray scattering (SAXS). All of the glass samples were in the early stage of diffusion controlled coarsening. However, while in the pure glass the volume fraction, w, of the droplets continuously approaches its reported equilibrium value, we, the w values of the doped glasses exceed considerably the value of we. These findings can be explained by the assumption that the additives MoO3 and WO3 give rise to an increase of Δµ resulting in a shift of the miscibility gap to higher temperatures. By means of in situ high-temperature SAXS experiments, it was proved that Tb of the doped glasses is really increased in relation to that of the base glass.