On the anisotropy in the HRTEM images of a decagonal quasicrystalline phase of the Al-Cu-Co-Si system

Abstract

Experimental evidence of an electrical and/or magnetic anisotropy was observed in the high resolution transmission electron microscope (HRTEM) images of a decagonal quasicrystalline (DQC) phase of the Al-Cu-Co-Si system. X-ray energy dispersive spectroscopy (EDS) spectra indicated a composition of Al$_{60}$Cu$_{23}$Co$_{15}$Si$_{2}$ for this phase. The anisotropy was responsible for poor contrast quality in the HRTEM images along the periodic direction of this phase, whereas good image contrast was observed in the quasi-aperiodic ten-fold plane. Comparing these results to findings previously reported for the Al$_{62}$Cu$_{20}$Co$_{15}$Si$_{3 }$DQC, we conclude that the observed anisotropy is strongly dependent on the selected chemical composition. After analyzing both the electrical and magnetic effects presented by a sample which is observed with an electron microscope, we conclude that the electrical properties of the DQC phase might be responsible for these observations.