Ionic conductivity in nano-scale CeO2/YSZ heterolayers

CeO2 based materials are promising candidates as solid oxide electrolytes within fuel cell systems. In this capacity, the oxygen anion conductivity is pivotal. Sata et al. [Nature, 2000, 408, 946–949] demonstrated the ability to ‘fine tune’ conductivities in BaF2 and CaF2 by generating BaF2/CaF2 heterolayers with different nanoscale film thicknesses. The resulting fluoride ion conductivities were found to be orders of magnitude higher compared with the component BaF2 and CaF2 materials. Similarly, it may be possible to fabricate CeO2 thin films with tuneable conductivities. In this study, we explore this possibility using atomistic simulation. In particular, simulated amorphisation and recrystallisation was used to generate an atomistic model for a CeO2/YSZ (yttrium stabilised zirconia) heterolayered system and, using this model, the ionic diffusivity, conductivity and associated activation energy barriers were calculated. However, in contrast to the BaF2/CaF2 system, the heterolayered CeO2/YSZ system did not exhibit exemplary transport properties compared with the parent materials. This study describes a framework simulation procedure, which can be used in partnership with experiment, to explore a variety of microstructural features that may facilitate an increase in the ionic conductivity of heterolayered systems.