Liquidus of MgO and MgAl ₂ O ₄ in the CaO‐MgO‐Al ₂ O ₃ System at 1550 and 1600°C

ABSTRACT In this study, the liquidus of MgO and MgAl 2 O 4 spinel phase in the CaO‐MgO‐Al 2 O 3 system at 1550 and 1600°C were experimentally investigated using a classical quenching method. In order to examine the liquidus composition accurately, the equilibration was carried out using four different ways using the combinations of Pt and ceramic (MgO and Al 2 O 3 ) crucible with starting materials of mechanical mixtures of CaO, MgO, and Al 2 O 3 powders and pre‐melted slag. The chemical compositions of liquid and solid phases after equilibration were analyzed using the electron probe microanalyzer (EPMA). Unlike the previous studies that relied on bulk chemical analysis of the slag containing dispersed spinel crystals, the present experimental study utilizes EPMA to successfully isolate the true liquid composition. In this way, the accurate liquidus of spinel phase in the CaO‐MgO‐Al 2 O 3 system at 1550 and 1600°C was determined for the first time. The liquidus of MgO in the present study was consistent with the available literature data.