Atomic-resolution STEM-EDS mapping of grain boundary solute segregation in yttria-stabilized zirconia

Yttria-stabilized zirconia (YSZ) is one of the primary choices for the electrolyte material in solid oxide fuel cells (SOFC), due to its excellent ionic conductivity at high temperatures. Nevertheless, such performance is usually limited by the ionic conductivity at grain boundaries, which is at least two orders of magnitude lower than that of bulk [1]. As a result, many studies have been performed to investigate grain boundary properties in YSZ, focusing on atomic scale structures and chemical inhomogeneity [2, 3]. Despite the fact that the Y segregation in the grain boundaries has been demonstrated [2], the atomicscale mechanism of how solute segregation occurs is still unclear. Probing the grain boundary at atomic scale is therefore critical for a basic understanding of the chemistry at such interfaces, which in turn will provide new strategies for the design of high performance materials. In this study, the local Y distributions near YSZ grain boundaries were directly determined by atomic-resolution elemental mapping using STEM-EDS, equipped with a high-sensitivity silicon drift detector (SDD).