X-Ray Topography of Decorated Dislocations in Magnesium Oxide

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Abstract
Combined x‐ray topographic and ultramicroscopic studies have shown a one‐to‐one correspondence between dislocation lines and chains of submicroscopic light‐scattering bodies within a magnesium oxide crystal in the ``as‐received'' state. Dislocations with any orientation and Burgers' vector were found to be decorated. The geometry and Burgers' vectors of various unusual dislocation configurations have been determined. These special configurations all arose from the extension of edge segments in the course of intense dislocation climb combined with a strong preference for a line orientation parallel to a cube direction. The relationship of such configurations to the general distribution of dislocations showed that the epoch of intense dislocation climb had occurred late in the evolution of the dislocation distribution. X‐ray diffraction evidence on whether the climb was due to the absorption of interstitials or of vacancies is as yet inconclusive.