TEM analysis of dislocation structures formed in the Cr-doped grain boundary of alumina

An alumina bicrystal with a Cr-doped {1̄100}/[0001] 2° low-angle tilt grain boundary was fabricated by diffusion bonding at elevated temperatures, and the microstructures around the grain boundary were observed by transmission electron microscopy. It was confirmed that an approximately 200nm width Cr-rich secondary phase was formed along the grain boundary. Not only an array of triply dissociated dislocations was introduced along the grain boundary but also misfit dislocations were introduced along the heterointerface between the Cr-rich secondary phase and the alumina matrix. By observing the heterointerface from the h1̄100i direction which is perpendicular to the plane, it was found that all the misfit dislocations dissociate into partial dislocations. The dissociation width was several times larger than that in alumina {1̄100} planes reported so far.