Abstract
Oxygen vacancy distributions and dynamics directly control the operation of solid-oxide fuel cells and are intrinsically coupled with magnetic, electronic, and transport properties of oxides. For understanding the atomistic mechanisms involved during operation of the cell it is highly desirable to know the distribution of vacancies on the unit cell scale. Here, we develop an approach for direct mapping of oxygen vacancy concentrations based on local lattice parameter measurements by scanning transmission electron microscopy. The concept of chemical expansivity is demonstrated to be applicable on the sub-unit cell level: local stoichiometry variations produce local lattice expansion that can be quantified. The vacancy mapping reveals strong difference in magnetic properties of lanthanum strontium cobaltite model systems induced by different substrate symmetry, opening pathways for structural tuning of the vacancy concentrations and their gradients.
