Phase relations in the ZrO2-Sm2O3-Y2O3-Al2O3 system. Experimental investigation and thermodynamic modelling

Sub-solidus phase relations in the ZrO2-Sm2O3-Y2O3 and Sm2O3-Al2O3-Y2O3 systems were experimentally studied at 1523-1873K and thermodynamic databases for these systems were developed. Analysis of phase equilibria in the Sm2O3-Y2O3-Al2O3 system indicated that REAM phase (Sm,Y)4Al2O9 is not stable in the Sm2O3 rich-composition. Therefore, the stability limit of the Sm4Al2O9 phase was established experimentally and thermodynamic parameters of the Sm2O3-Al2O3 system were re-optimised. The eutectic melting in the Sm2O3-Y2O3-Al2O3 system was investigated using differential thermal analysis and scanning electron microscopy. The results obtained were used to assess the mixing parameter of the liquid phase. A new description of binary system was introduced into the database of the ZrO2-Sm2O3-Al2O3 system and phase diagrams were re-calculated. The obtained thermodynamic databases were combined with literature data for the ZrO2-Y2O3-Al2O3 system and a thermodynamic database for the ZrO2-Sm2O3-Y2O3-Al2O3 system was developed. (orig.)