Observation by X-ray topography of the climb of dislocations during the oxidation of zinc single crystals

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Abstract
Monocrystalline slabs of zinc have been prepared with a high degree of perfection. Their dislocation configurations are observed by transmission X-ray topography. The evolution of these configurations is studied while undergoing oxidation at room temperature. Dislocation lines with a-type Burgers vector are shown to climb. Long edge dipoles grow on those which exhibit a strong edge character. Hexagonal loops with c-type Burgers vector grow by climb in the basal plane up to a size of about 200 microns for a three-month oxidation. Rhombus-shaped imperfect loops with ½c+p type Burgers vector are also shown to grow with time. The geometry and Burgers vector of the dislocations could be determined unambiguously from the observation of numerous topographs obtained with different reflecting planes. The evolution of the dislocations is attributed to the vacancy supersaturation created in the crystals by the oxidation process.