Structure transition in a ZnO grain boundary

The structure of a \[0001]/31.5o tilt boundary in ZnO has been investigated using high-resolution electron microscopy. In some regions the interface structure is best described by reference to the periodic dichromatic pattern corresponding to the misorientation \[0001]/32.5o ( Sigma = 13). These regions exhibit arrangements of periodic facets with localized interfacial dislocations (having primitive Burgers vectors) superimposed upon them. Other regions are better described by reference to the dichromatic pattern corresponding to \[0001]/30o which is periodic parallel to \[0001]only. These segments of interface are parallel to (0110) and (1120) in the adjacent crystals and their structure is incommensurate perpendicular to \[0001]. No localized defects were found in such segments. A model is proposed for the progressive structural transition of interfaces in the misorientation range between the two singular values. It is suggested that the observation presented is a composite of the two structural forms, one special and the other more general, corresponding to an intermediate misorientation.