Application to Ceramic Interfaces

Abstract

Grain boundaries and interfaces of ceramics have peculiar atomic and electronic structures, caused by the disorder in periodicity, providing the functional properties, which cannot be observed in a perfect crystal. These structures are also influenced by the grain boundary and interface characters such as misorientation angle, grain boundary plane, lattice misfit and so on. In the vicinity of the grain boundaries and interfaces around the order of 1 nanometer, dopants or impurities are often segregated, and they play a crucial role in the material properties. STEM utilizing the Cs corrector enables us to identify the atomic columns and the location of the dopants on the grain boundaries and interfaces. In this chapter, after reviewing the general concept for grain boundary and interface, the latest results obtained by STEM are shown for low angle grain boundaries (dislocation boundary), coincidence site lattice (CSL) grain boundaries, grain boundary segregation, amorphous grain boundary, coherent and incoherent hetero-interface structure in various ceramics. In addition, new STEM techniques including annular bright field (ABF) is demonstrated for directly observing light elements which are main constituent components in ceramics. Several STEM images are analyzed to understand the structure-property relationship by the first principles calculation based on the observation results.