Critical Evaluation and Thermodynamic Modeling of the RE 2 O 3 –MgO Systems (RE = All Lanthanides + Sc, Y)
Jeong‐Min Cheon, Kerui Lai, In‐Ho JungABSTRACT
The RE 2 O 3 –MgO binary systems provide fundamental phase‐equilibria information for high‐temperature oxide ceramics, including MgO‐based refractories modified with rare‐earth oxides and RE 2 O 3 ‐based advanced ceramic materials used in semiconductor‐processing and aerospace applications. In this study, thermodynamic modeling of the RE 2 O 3 –MgO binary systems (RE = all lanthanides, Sc, and Y) was performed based on a critical and systematic evaluation of available experimental phase diagram data. All the experimentally investigated RE 2 O 3 –MgO systems exhibit simple eutectic phase diagrams without intermediate compounds, accompanied by MgO solubility in RE 2 O 3 , and the same features are predicted for the unexplored systems from the systematic trends across the series. From experimental data for 12 RE 2 O 3 –MgO systems (RE = La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Lu, Sc, and Y), systematic trends in eutectic compositions and temperatures, MgO solubility in RE 2 O 3 solid solutions, and thermodynamic properties of liquid and solid solutions were identified. These trends were used to conduct consistent thermodynamic modeling of the entire RE 2 O 3 –MgO series and to predict the phase diagrams and thermodynamic properties of the five unexplored RE 2 O 3 ‐MgO systems (RE = Pm, Eu, Tb, Ho, and Tm), for which no direct experimental phase‐equilibria data are available. This work, for the first time, presents complete and internally consistent thermodynamic descriptions of the entire RE 2 O 3 –MgO system series.