Dislocations Observed in NaF Crystals. II. Nucleation Sources on Cleavage Surfaces

Abstract

Dislocation loop families beneath the cleavage face have been studied three-dimensionally by means of the electrolytic coloration. Emerge planes are {110} and (001). Dislocations at shallow levels are strongly influenced by image force, i. e. freed from the face or changed their shape. The nucleation sources of dislocation are found at structural inhomogeneities where stress concentration occurs during the cleavage and electrolysis. Simple loop families are relatively isolated from each other, while complicated ones are observed to be close together with the multiform neighborhood. The mechanisms of nucleation and complication are discussed for each dislocation loop family, from simple to complicated ones including newly found chevron patterns.