Defect cluster formation in M2O3-doped cubic ZrO2

Atomistic simulation calculations based on energy minimization techniques have been used to study the energetics associated with M2O3 solution in ZrO2. Results predict that the binding energy of an oxygen vacancy to one or two substitutional cations is a strong function of dopant cation radius. Oxygen vacancies occupy sites that are first neighbour with respect to small dopants whereas oxygen vacancies are located in second neighbour sites with respect to large dopants. The crossover occurs at approximately Sc3+, which also exhibits the smallest binding energy. This behaviour is a consequence of long-range relaxation of the oxygen sublattice. The model is validated by comparing predicted lattice parameters of M2O3:ZrO2 solid solutions with experimental data.