Effect of divalent cations and SiO2 on the crystallization behavior of calcium aluminate glasses

Abstract Calcium aluminate glasses are of technological interest due to their excellent optical and mechanical properties. However, the glass-forming ability (GFA) and glass stability (GS) of these systems are poor, with the best binary CaO–Al 2 O 3 glass-forming composition occurring at the eutectic point (64CaO–36Al 2 O 3 , in mol%). In this work, we have investigated the crystallization processes of CaO–Al 2 O 3 based glasses with different additives (SiO 2 , MgO, SrO, BaO, and ZnO) during dynamic and isothermal heating. It is found from X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses that both the dynamic and isothermal glass stabilities increase with the initial addition of SiO 2 . The glass stability parameter K SP increases from 3.4 to 11.0 K upon the addition of 10 mol% to the eutectic CaO–Al 2 O 3 composition, but then decreases upon further addition of SiO 2 . Partial substitution of CaO for different divalent cation oxides also increases the GS, with the largest impact found for the cations with the greatest difference in ionic radius compared to Ca 2 + . For example, when 10 mol% of MgO is substituted for CaO, K SP increases from 3.4 to 6.9 K. These results are useful for designing new CaO–Al 2 O 3 based glasses that can be produced on an industrial scale.