The grain boundary structure of [001] symmetric tilt boundary with a tilt angle of 66° was investigated using a rutile-type TiO2 bicrystal. The tilt angle of this boundary had a misfit angle of 1.7° from an exact Σ13 approaching to Σ17 relation. High-resolution transmission electron microscopy study had revealed that the grain boundary was free from any secondary phases, and the two single crystals contact each other perfectly at an atomic scale. The boundary exhibited almost straight features without any step structures whereas part of the boundary formed facet structures consisting of low-index planes such as {310} and {110}. On the other hand, it was found that the contrast due to strong strain fields existed on the grain boundary plane with a spacing of 7.6nm by weak beam dark field observation. Comparing with atomic structural analysis using high-resolution transmission electron microscopy study, the strain field results formed a distorted Σ13 unit structure, which could be predicted from a rigid body model of Σ13 relation. This distorted unit structure had a similar structure of Σ17 relation. Namely, the boundary consists of a periodical array consisting mainly of Σ13 unit structures and partially Σ17-like unit structures. In other words, a misfit angle in this boundary was accommodated by not introducing secondary dislocations, but a transformation of basal unit structure.

High Resolution Microscopy Study for [001] Symmetric Tilt Boundary with a Tilt Angle of 66° in Rutile-Type TiO2 Bicrystal. Ohno, T., Ii, S., Shibata, N., Matsunaga, K., Ikuhara, Y., Yamamoto, T.: Materials Transactions, 2004, 45[7], 2117-21