Effect of morphology on helium mobility in soda-lime-silica glasses

Helium permeability has been measured for a wide range of soda-lime-silica glasses. The results have been used to define the interconnectivity and miscibility limits for this glass-forming system. Results of heat-treatment studies have also been used to determine the interconnectivity boundary temperature for the 2Na2O⋅CaO⋅XSiO2 compositional line. It has also been shown that the replacement of Na2O by CaO substantially reduces the mobility of helium in those glasses lying outside the immiscible region.