Interfaces in ceramics play an important role on the various properties. It has been known that the addition of small amount of dopants strongly improve the mechanical and functional properties in polycrystalline ceramics. Z-contrast images obtained by scanning transmission electron microscopy (STEM) is powerful technique to experimentally determine the location of the dopants segregated at grain boundaries and interfaces. As the image intensity in the Z-contrast is approximately proportional to the square of the atomic number, STEM technique is especially well suited for understanding the role of heavy impurities in grain boundaries and interfaces composed of much lighter ions. In this review paper, our recent results obtained for ceramic grain boundaries and interfaces by Cs-corrected STEM are introduced. Several examples are demonstrated for the gain boundaries of varistor and structural ceramics, dislocation in alumina, oxide superlattice, lithium battery and so on. These results indicate that the atomistic mechanism of the properties can be unraveled by the combination of STEM characterization and the first principles calculations. This approach will be a breakthrough for new materials science and engineering in the next generation.%結晶の粒界や界面は，周期性の乱れに起因する特異な電子rn構造を有しており，完全結晶にほ見られない機能発現の起源rnとなっている．このような粒界・界面近傍1ナノメートルrnオーダーの局所領域にはドーバソトや不純物が偏在し，これrnがその材料機能に決定的な役割を持つことが多い．
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