The magnitude of the Burgers vectors of glissile <c>-component dislocations, that were observed in polycrystalline samples after room-temperature compression, was determined directly by using transmission electron microscopy. In previous studies, only the direction of the Burgers vectors of this type of defect had been definitely determined by experiment. Direct experimental determination of the Burgers vector was achieved here by combining conventional diffraction contrast methods with a detailed analysis of the effects of these <c>-component dislocations upon thickness contours. The defects which were responsible for the limited accommodation of strains with components out of the basal plane (c-component strains) during room-temperature deformation were identified as being pairs of (c+a/2) super-partial dislocations, with Burgers vectors of b = 1/6<¯21•6>, which delineated a ribbon of antiphase boundary on {¯21•1} second-order pyramidal planes.

J.M.K.Wiezorek, C.J.Humphreys, H.L.Fraser: Philosophical Magazine Letters, 1997, 75[5], 281-9