Experimental Determination of the Liquidus in the High-Basicity Region in the Al₂O₃(25 mass pct)-CaO-MgO-SiO₂ and Al₂O₃(35 mass pct)-CaO-MgO-SiO₂ Systems

Liquidus in the Al₂O₃(25 mass pct)-CaO-MgO-SiO₂(<20 mass pct) and Al₂O₃(35 mass pct)-CaO-MgO-SiO₂(<20 mass pct) systems were determined experimentally in the high-CaO-containing region at 1873 K (1600 °C). For the Al₂O₃(35 mass pct)-CaO-MgO-SiO₂(<20 mass pct) system, liquidus data were also determined for 1773 K (1500 °C). The equilibrating and quenching technique with subsequent electron probe microanalyzer (EPMA) microanalysis were employed. Based on the data, liquidus lines were constructed for the 25 and 35 mass pct alumina planes at silica contents generally below 20 mass pct. The current results showed a slightly lower solubility of CaO and a higher solubility of MgO at 1873 K (1600 °C) for the 25 mass pct Al₂O₃ section compared with the existing phase diagram. At 1773 K (1500 °C), the result showed a slightly lower solubility of both CaO and MgO in the 35 mass pct Al₂O₃ section compared with the existing phase diagram. In addition, the activities of MgO, CaO, and Al₂O₃ were estimated at 1773 K and 1873 K (1500 °C and 1600 °C) using the phase diagram information.