Atomic Scale Origin of Enhanced Ionic Conductivity at Crystal Defects.

In oxide materials, the presence of dislocations often strongly affects the properties of thin film and multilayer devices. Although it was reported that ionic conduction can be enhanced by introducing dislocations in ionic conductors, the underlying mechanism of such enhancement remains unclear. Here we analyzed the ionic conduction enhancement in an yttria-stabilized zirconia (YSZ) single edge dislocation from a structural point of view, using atomic resolution scanning transmission electron microscopy (STEM). First, the atomic structure and chemistry of a dislocation in YSZ were characterized by STEM and energy dispersive X-ray spectroscopy (EDS). A relative ionic conduction variation map around the dislocation was then estimated based on the well-established strain-conductivity and chemistry-conductivity relationships in YSZ. We propose that a faster ionic conductivity path can be formed around the dislocation core due to the coupling of the tensile strain field and dopant segregation, which could account for enhanced ionic conductivity along dislocations.