Abstract

Defects in AgCl tabular grains with {111} surfaces are characterized by transmission electron microscopy (TEM) and their influence on the growth process is discussed. In the tabular crystals, twins parallel to the tabular face as well as dislocations along different directions are observed. The twins induce the tabular growth, while the dislocations do not influence the morphology. In 10 to 30% of the crystals that have been characterized, thickness growth is observed and it is shown that in all cases twins on other planes than the tabular ones are present. Two configurations occur more frequently and are analyzed in detail. For the first group, twins parallel to the tabular face as well as a microtwin along a non-parallel {111} plane that ends inside the crystal are present. In the crystals of the second group, only one extra non-parallel twin occurs giving rise to a bicrystal built up by a tetrahedral shaped part and a flat triangular or trapezoidal part. More complex twin configurations give rise to various, less characteristic morphologies. From these observations, it appears that the thickness growth is related to the presence of the twins on planes other than on the tabular ones.(Author abstract)