Phason Related Stacking Disorder in Decagonal Al-Co-Ni

High-resolution transmission electron microscopy images of decagonal Al-Co-Ni quasicrystals are presented, which show the existence of phason related stacking disorder along the periodic tenfold axis. The image contrast in the interior of hexagon-shaped tiles shows an inner vertex only if no phason defect is present. This interpretation of the high-resolution micrographs is substantiated by electron microscopic image simulations based on a realistic structure model.