The fabrication of a ternary eutectic ceramic composite by rapid quenching in the system Al2O3-Y2O3-ZrO2 prompted us to study the solidification behavior and phase formation from melts of three-phase composites in the ternary oxide phase diagram. Solidified phases were determined by X-ray diffraction (XRD) and Raman spectroscopy. The occurrence of cation substitution in the stoichiometric phases, promoted by the rapid phase separation during quenching and the composition of solid solutions in the quenched composites were investigated. The results were used to determine the compositional limits of solid-phase regions, in order to construct a tentative subsolidus diagram for arc-image melted composites.The microstructural study indicates that it is feasible to fabricate ternary eutectic composites containing zirconia in the system by rapid quenching, even at cooling rates above 10(3) K s(-1). Eutectic composites with the zirconia-based ionic conductor phase have excellent prospects for a wide range of high temperature applications in technological devices.