A cluster-modeling study of the structure of yttria-stabilized zirconias

The Zr and Y coordination polyhedra, as found in the room-temperature phases of their pure oxides, are used as building blocks in modeling the structures of yttria-stabilized zirconias (YSZ). It is found that, in order to obtain the right coordination geometry, three clusters of four Zr- and Y-based building blocks can be constructed. When Y building blocks are present in a cluster they form a couple, characterized by a common structural vacancy, a neutral defect which can be defined when an oxygen is missing with respect to the case of the Zr seven coordination in monoclinic zirconia. It is shown that this model fairly well justifies the experimental results obtained by others. In conclusion, this kind of cluster modeling is proposed as a general method for solving structural problems in other mixed oxides