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The densities of quaternary glass-forming systems within the CaO-MgO-Al 2 O 3 -SiO 2 -composition (CMAS) were evaluated. Their compositions differed not more than 5 mol% for each component from each other. After melting, the exact chemical compositions were measured using X-ray fluorescence and the densities were determined by Archimedes method and pycnometry. This property and its dependency upon small variations in the composition is the main focus of this paper.The density values were between 2.617 and 2.700 g/cm³ and the packing density factors V p of the oxide glasses using the ionic radii of Pauling ranged from 0.562 to 0.574. The experimentally determined data were compared to different model calculations. Calculations performed according to empirical formulae given in the literature showed relative deviations between À5 and 12% to the experimental values. The effect of MgO was also studied by comparing the glasses with similar compositions (Ceram Int, 2016;42:5810-5822 ) without any MgO.

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Thermal properties of ternary glass-forming systems within the known CaO-Al 2 O 3 -SiO 2 system were evaluated. Different glass compositions near the lowest eutectic composition (around a liquidus temperature of 1170°C) within the CaOAl 2 O 3 -SiO 2 system were melted from pure raw materials. The investigated target range of compositions in wt% was between 60.5 and 63.5 SiO 2 , 13.1 and 16.1 Al 2 O 3 , and 21.4 and 25.4 CaO. The chemical compositions, the glass transition temperatures, and the temperatures attributed to viscosities of 10³ dPa*s were determined experimentally. It was of special interest to obtain information of all these properties of the glasses and the effect of small composition changes hereon. The liquidus temperature changed less than expected for a composition close to the eutectic composition. Temperatures at a viscosity of 10³ dPa*s varied between 1263 and 1363°C AE 6°C. A liquidus temperature of 1157°C AE 7°C (with a confidence interval of 95%) of the eutectic composition was found. The results reported here may be useful for understanding and improvement of the modeling within the CaO-Al 2 O 3 -SiO 2 glass system.

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