Segregation to the grain boundaries in YSZ bicrystals: A Molecular Dynamics study

A Molecular Dynamics study about the segregation of yttrium at 1500 K to a Σ5 grain boundary in 8 mol% YSZ has been performed. Segregation has been induced by explicitly taking into account the excess energy associated to the elastic misfit effect for yttrium cations located nearby the grain boundary planes. After an initial transient, a steady regime is reached, in which the number of yttrium cations does not increase with time. Accumulation of yttrium cations is accompanied by that of zirconium ones and oxygen vacancies at some distance of the grain boundary planes. The changes in the radial distribution functions for different ionic pairs are discussed, as also the effect of segregation on oxygen diffusion along the grain boundaries and in volume. Finally, the possibility that segregated yttrium located at available free sites at the grain boundaries is pointed out.

► Yttrium segregation to a Σ5 GB in YSZ by elastic misfit effect has been studied.
► Segregated cations accumulate preferentially at the GB planes.
► Segregation causes a local depletion of the number of zirconium and oxygen vacancies.
► Segregation increases the number of second neighbors for Y ′ Zr–Y ′ Zr pairs at the GBs.
► Segregation affects bulk diffusion of oxygen, but not GB diffusion.