Phase diagram of the Al2O3–HfO2–Y2O3 system

The phase diagram of the Al2O3-HfO2-Y2O3 system was first constructed in the temperature range 1200-2800 C. The phase transformations in the system are completed by eutectic reactions. No ternary compounds or regions of appreciable solid solution were found in the components or binaries in this system. Four new ternary and three new quasibinary eutectics were found. The minimum melting temperature is 1755 C and it corresponds to the ternary eutectic Al2O3 + HfO2 + Y3Al5O12. The solidus surface projection, the schematic of the alloy crystallisation path and the vertical sections present the complete phase diagram of the Al2O3-HfO2-Y2O3 system.