Grain boundary and interface structures in ceramics

This paper reviews grain boundary and interface structures in ceramics. Fir stly, geometrical treatments are briefly described for both grain boundary and hetero-interface. For the grain boundary, grain boundary character, sma ll angle grain boundary, coincidence site lattice (CSL) theory, structure u nit, segregation and amorphous grain boundary are reviewed to show a couple of examples observed in ceramics. For the hetero-interface, O-lattice theo ry, lattice coherency and interfacial dislocation are discussed and the res ults obtained for metal/ceramics interfaces are introduced. Transmission el ectron microscopy (TEM) enables us to characterize the very narrow regions less than 1 nm, and therefore is powerful technique for investigating grain boundary and interface structures. In this paper, recent experimental TEM studies are presented to demonstrate grain boundary and interface character ization at high spatial resolution.