Phase relationships in the system Y₂O₃-ZrO₂

Summary

• 1. A new phase diagram is proposed for the system Y₂O₃-ZrO₂ in the solid phase, differing from that of Duwez and co-authors by the presence of a compound Y₂Zr₂O₇, by the absence of a single-phase region of the monoclinic solid solution, and also by the different position of the phase boundaries of the solid solutions in the system.

• 2. The minimum amount of Y₂O₃ needed for complete stabilization of ZrO₂ depends to a considerable extent on the roasting temperature.

• 3. The reduction in the temperature of the polymorphic transformation of zirconium dioxide roasted with small additions of stabilizing oxides can be explained by the change in the repulsive force between the cations in the ZrO₂ lattice due to the formation of a monoclinic substitutional solid solution of zirconium dioxide, the degree of reduction in the temperature of polymorphism depending on the size of this change.