Cation segregation in Nb16W18O94 using high angle annular dark field scanning transmission electron microscopy and image processing

We report the characterization of the complex oxide Nb₁₆W₁₈O₉₄ using high angle annular dark field imaging at 200 kV in a scanning transmission electron microscope. The results of this study suggest that the W and Nb cations are not uniformly distributed among the cation columns projected along 001] but that there is preferential segregation of the heavier species to certain column sites. In order to analyse the experimental data obtained, an image processing methodology has been developed which may also find application in locating specific motifs within a generally distorted image field.