Dislocation dissociation in low-angle spinel boundaries

Abstract

It is well known that in the spinel structure a perfect dislocation can dissociate into two partial dislocations with collinear Burgers vectors :(1)The two partial dislocations, which have the same character as the perfect dislocation, are separated by a stacking fault in the cation sublattice only. In ceramic materials, unlike fcc metals, dissociation of dislocations can occur by a climb mechanism in addition to, or instead of, dissociation by glide. Climb dissociation of perfect dislocations into two or more partials with collinear Burgers vectors has been observed in e.g. yttrium iron garnet and sapphire. Previous studies in spinels, deformed at high temperatures, emphasize climb dissociation and dissociation of mixed character. Dissociation of screw dislocations in stoichiometric MgAl2O4 spinel could not be resolved and hence no experimental measurements of the dissociation width have been reported.