Physicochemical Interaction in the Al2O3–HfO2–Ln2O3 Systems

Experimental data are used for the first time to refine the prediction of elements in the Al 2 O 3 –HfO 2 –Ln 2 O 3 phase diagrams and confirm the prognosis for three-phase eutectics in the Al 2 O 3 -rich regions. It is established that a series of eutectics solidify through cooperative solidification of the phases. The highest melting temperature in the system is 2820°C, corresponding to the HfO 2 melting point. The minimum melting temperatures in the systems range from 1600 to 1760°C and correspond to the melting points of Al 2 O 3 -rich three-phase eutectics. Materials in these systems are promising for the development of high-temperature structural composites based on directly solidified two-phase and three-phase eutectics, materials for thermal barrier coatings, materials for solid electrolytes (SOFCs, oxygen sensors, etc.), and refractories.