Secondary Grain-Boundary Dislocations in (001) Twist Boundaries in MgO. 1. Intrinsic Structures

摘要

Intrinsic secondary grain boundary dislocation (GBD) structures were observed by weak beam transmission electron microscopy in a variety of (001) twist boundaries in MgO prepared by a welding technique. Square networks of intrinsic screw GBDs were found in boundaries possessing twist deviations from the exact = 1, 5, 13, 17, 25, 29 and 53 Coincidence Site Lattice (CSL) misorientations. ( = fraction of lattice sites in coincidence). These GBDs were all perfect GBDs with Burgers vectors given by the primitive vectors of the corresponding DSC-Lattice except in the case of = 13 where a square array of partial screw GBDs was observed. Arrays of screw GBDs were not detected in a number of high boundaries. Super-imposed arrays of edge type intrinsic GBDs were observed in all boundaries when a small tilt component was present. (ERA citation 07:044197)