Spectroscopic examination of clean glass surfaces at elevated temperatures

Glass melt surfaces have been analyzed at elevated temperatures in situ with ion scattering spectroscopy (ISS). The surface composition of alkali trisilicate glasses is found to be dependent upon the relative fluxes of alkali ions out of the surface due to evaporation and to the surface due to bulk diffusion. At temperatures within and below the glass transition range T_g, the surface composition is very sensitive to time and temperature. However, at temperatures greater than T_g, the bulk diffusion flux replenishes the alkali surface sites rapidly. Thus, the surface composition of the liquid surface is relatively insensitive to time and temperature.