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Published online by Cambridge University Press: 31 January 2011
In order to clarify inconsistencies in the literature and to verify assumed ternary solubilities, the phase equilibria in the Y2O3–Al2O3 –SiO2 system at 1600, 1400, and 1300 °C were experimentally determined using x-ray diffraction (XRD), scanning electron microscope with attached energy-dispersive detector system (SEM-EDX), and electron probe microanalyzer (EPMA). Six quasibinary phases were observed: Y4Al2O9 (YAM), YAlO3 (YAP), Y3Al5O12 (YAG), Y2SiO5, Y2Si2O7 (C and D modifications), and ˜3Al2O3· 2SiO2 (mullite). Y4Al2O9 forms an extended ternary solid solution with the formula Y4Al2(1-x)Si2xO9+x (x = 0 2 ˜0.31). The lowest ternary eutectic temperature was determined at 1371 ± 5 °C by high-temperature differential scanning calorimetry (DSC). The results were compared with previous data available for the Y2O3–Al2O3 –SiO2 system and with data for other RE2O3–Al2O3 –SiO2 (RE = rare earth element) systems.