Phase Relationships in the System Zirconia—Ceria

Abstract

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.