Phase Relationships in the System Zirconia—Ceria

The phase relationships in the system zirconia-ceria were investigated by X-ray diffraction and dilatometric methods. The specimens were prepared by mixing and compacting the oxide powders and firing at 2000°C. At 2000°C. zirconia and ceria are miscible in each other from about 24 to 100 mole % ceria. The range of solid solubility decreases markedly with temperature, so that near 1000°C. the solubility of zirconia in ceria is only about 10 mole %. The addition of 0 to 1.5 mole % ceria lowers the temperature at which zirconia transforms from the tetragonal to the monoclinic form. Near 15%, therefore, this temperature is below room temperature and zirconia is stabilized. On the basis of these results, a tentative phase diagram of the system zirconia-ceria is presented. Experiments also have been conducted with zirconia containing 13.8 mole % magnesia (stabilized zirconia). In this case the solubility between stabilized zirconia and ceria is complete at high temperature (2000°C.). At lower temperature, however, the solid solution breaks down and a two-phase region appears in the center of the diagram.