Fig. 3: Inverse correlation of m-MRD for Group II 20 MgO/CaO NAS glasses.

a Compositions of Ca-NAS (red) and Mg-NAS (blue) glasses, as shown in the ternary phase diagram in mol%. b Fragility values (m) as a function of Al₂O₃ mol% for ten Ca-NAS (red) and ten Mg-NAS (blue) glasses. The changing trends of m are in line with the changing trends of MRD (e) derived from the room-temperature F(Q)-FSDPs for Mg-NAS (c) and Ca-NAS (d) glasses. In (c) and (d), the arrow indicates the direction of Al₂O₃ mol% content increase; the red color pattern is for non-Al₂O₃ containing glass, while the black color pattern is for the highest 24 mol% Al₂O₃ glass. Ca-glasses generally have higher m values than do Mg-glasses; the m values of Ca-glasses are independent of the Al₂O₃ mol%, while m values for Mg-glasses increase with increasing Al₂O₃ content. Accordingly, Ca-glasses show overall lower MRD values than those of Mg-glasses; no significant difference is shown for Ca-glass MRDs, in contrast to the MRD values of Mg-glasses, which decrease systematically with increasing Al₂O₃ mol% content.