Phase Relations at 1500°C in the Ternary System ZrO2–Gd2O3–TiO2

Phase relations at 1500°C in the ternary system ZrO2–Gd2O3–TiO2 have been determined by the powder X-ray diffraction of samples prepared by standard solid state reaction. A large area of this ternary oxide system centered on the Gd2Ti2O7–Gd2Zr2O7 join was shown to exhibit the pyrochlore and defect fluorite structures. The pyrochlore structure was observed for stoichiometries as far from the ideal M4O7 as M4O6.7 and M4O7.4, although the degree of disorder seemed much higher at these stoichiometries. On further deviation from the ideal M4O7 stoichiometry a smooth transition to fluorite average structure was observed for Zr-rich compositions. None of the other binary phases were observed to show significant extent of solid solution into the ternary region.