Abstract:
Large silver bromide rod crystals have
been grown in a solution of silver bromide and potassium bromide in dimethyl
sulfoxide. Samples of these crystals were examined
by scanning electron microscopy in order to study their side and top face
structure. Crystal sides were bounded by {111} and {100} faces. Rod crystals
grown from concentrated solutions developed a well-defined top face structure
composed of alternating {111} and {100} faces. However, they showed a relatively
small length to thickness ratio. On the other hand, top faces of fast growing
rod crystals were rough. Slices of rod crystals were examined by transmission
electron microscopy to study their twin plane structure, for the first
time. All the rod crystals examined showed non-parallel twin planes of
(111) type. Surprisingly, all of them also showed parallel twin planes.
Rod crystals can transform into tabular or tetrahedral crystals either
by formation of new twin planes, or by overgrowth of some twin variants
over others in processes that start at the tips of the rod.