Effect of Small Additions of Al ₂ O ₃ and Ga ₂ O ₃ on the Immiscibility Temperature of Na ₂ O‐SiO ₂ Glasses

Abstract

Alumina and gallia were substituted separately for Na 2 O in amounts of 0.2, 0.5, 1.0, 1.5, 2.0, and 3.0 wt% in three Na 2 O‐SiO 2 glass compositions (82, 84, and 86 wt% SiO 2 ) within the immiscibility region. The immiscibility regions for each system extend to ∼1.5 mol% of the added oxide. In general, the addition reduced the immiscibility temperature ( T m ), but at the edge of the immiscibility region (82% SiO 2 ) the Na 2 O loss effect initially increased T m . A structural model of the miscibility of Al 2 O 3 added to silicate glasses is presented.