Dislocations studies in β-silicon nitride

Abstract

Some preliminary results of dislocation analysis and associated glide systems in as-grown as well as in superplastically deformed β silicon nitride are presented. Transmission electron microscopy observations using the weak-beam technique, are reported. [0 0 0 1] {1 0 1 0} and 1/3〈1 2 1 0〉 {1 0 1 1} glide systems have been characterized. In the basal plane, a superposition of two hexagonal networks built with screw dipoles has been observed. Both a sequence extended node–constricted node and partial dislocations have been identified in these networks which clearly evinces dislocation dissociation in β-silicon nitride following the reaction 1/3〈2 1 1 0〉→1/3 〈1 0 1 0〉+1/3 〈1 1 0 0〉.