Observation of oxygen vacancy ordering and segregation in perovskite oxides

Oxygen vacancies are known to dominate the overall electrical behavior of perovskite oxides, which are used in many applications. Although theories have been developed to explain the effect of these vacancies and the defect chemistry of perovskites, there has yet to be incontrovertible evidence of the fundamental origins of the structure-property relationship. However, recently developed technologies in scanning transmission electron microscopy, such as Z-contrast imaging and EELS combined with in-situ heating experiments, provide a new opportunity to address vacancy characteristics and defect chemistry on the basic atomic level. In this paper we discuss the practical aspects of these techniques and demonstrate their application to the characterization of defect chemistry and vacancies in ordered micro-domains, at domain boundaries and at grain boundaries.