Large dislocation loops in antimony telluride

When slowly grown from the melt, antimony telluride contains large hexagonal loops. The observations suggest that these are prismatic loops resulting from deviations of the stoichiometric composition. In particular it is proposed that tellurium vacancies precipitate in prismatic loops, from which the ‘geometrical’ stacking fault is eliminated, by glide of a partial. An explanation is given for the occurrence of pairs of concentric loops elongated in direction differing by 60°. The equilibrium shape as calculated on the basis of the model agrees reasonably well with the observed shape.