While yttrium and impurity segregation at interfaces of yttria-stabilized zirconia was intensively studied experimentally, the mechanisms governing the propensity for segregation were still not fully understood. The segregation energetics of yttrium and aluminium, another common segregant at interfaces of yttria-stabilized zirconia, were studied by means of first principles calculations based on density functional theory. Site-dependent formation energies were calculated following the substitutional incorporation of yttrium and aluminium in the near-interface region of the Σ5(310) grain boundary in cubic zirconia, for which recent experimental data revealed strong yttrium enrichment. Aluminium segregation was found to be strongly favoured, accompanied by extensive changes in its local environment and coordination. Yttrium displayed a segregation propensity dependent on the site of substitution that correlated with the ability of its surrounding environment to accommodate the misfit strain by a breathing-type relaxation and increase of the nearest-neighbor yttrium–oxygen distances. Formation energies of oxygen vacancies were also determined near the interface, both as isolated defects and also by considering co-segregation with yttrium; the ensuing defect association led to stable yttrium–vacancy complexes and increased the energy gain from yttrium incorporation at the core of the grain boundary.

First Principles Study of Segregation to the Σ5(310) Grain Boundary of Cubic Zirconia. A.G.Marinopoulos: Journal of Physics - Condensed Matter, 2011, 23[8], 085005