Isothermal sections of the Al^sub 2^O3-HfO2-Er^sub 2^O3 phase diagram at 1250 and 1600°C

The isothermal sections at 1250 and 1600°C for the Al^sub 2^O3-HfO2-Er^sub 2^O3 phase diagram are constructed for the first time. Phase equilibria are established at these temperatures; they are determined by the most thermodynamically stable compound, HfO2. No ternary compounds or appreciable solid-solution regions based on components or binary compounds are found in the ternary system. The presence of AL + F, Er^sub 3^A^sub 5^ + F, ErA + F, and Er^sub 2^A + F two-phase regions on the isothermal section at 1650°C suggests that they contain triangulating sections of the Al^sub 2^O3-HfO2-Er^sub 2^O3 ternary system.[PUBLICATION ABSTRACT]