Physicochemical Interaction in the Al₂O₃–HfO₂–Ln₂O₃ Systems

Abstract

The experimental findings are used for the first time to refine the prediction of elements in the phase diagrams for Al₂O₃–HfO₂–Ln₂O₃ systems, which are still to be examined, and the prognosis for three-phase eutectics in the Al₂O₃-rich regions is experimentally confirmed. It is established that a series of eutectics solidify through cooperative crystallization of the phases. The highest melting temperature in the system is 2820 °С, corresponding to the HfO₂ melting point. The minimum melting temperatures in the systems range from 1600 to 1760 °С and correspond to the melting temperatures of the Al₂O₃-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.