Impact of segregation energetics on oxygen conductivity at ionic grain boundaries

In pursuit of whether nanocrystallinity could lead to higher anion conductivity, research has revealed contradicting results exposing the limited understanding of point defect energetics at grain boundaries (GBs)/interfaces. By disentangling and addressing key GB energetics issues related to segregation, migration and binding energies of oxygen vacancies in the presence and absence of dopants at the GBs, as well as the segregation energetics of dopants, we use atomistic simulations of doped nanocrystalline ceria to elucidate that dopant segregation is the key factor leading to degradation of oxygen conductivity in nanocrystalline materials. A framework for designing enhanced conducting nanocrystalline materials is proposed where the focus of doping strategies shifts from the bulk to segregation at GBs.