Identification of planar defects in D019 phases using high-resolution transmission electron microscopy

An analysis based on crystal symmetry and high-resolution transmission electron microscopy (HRTEM) is presented as a general methodology to identify planar defects on the basal planes of D019 compounds. As a starting point, the possible (close-packing preserving) planar defects are classified in accordance with their visibility, and the magnitude of the displacement vector on prismatic projections. Analysis of experimental HRTEM images, obtained under two different viewing conditions, followed by matching with simulated images, enables unambiguous identification to be made. The methodology is applied to planar defects observed in D019 Co3W, which are identified as π rotations around [0001]. To the best of our knowledge these defects have not been identified before in D019 phases.