Icosahedrally Related Decagonal Quasicrystal in Rapidly Cooled Al-14-at.%-Fe Alloy

Abstract

A decagonal quasicrystal with point group 10/mmm has been found in Al-14-at.%-Fe alloy. Zone-axis patterns of the decagonal phase appearing at the icosahedral positions are reminiscent of the appropriate icosahedral patterns. The symmetry and the angular separation of the zone axes can be obtained from the icosahedral phase by the addition of a mirror plane normal to a fivefold axis. This is supported by the observed diffuse streaking parallel to the tenfold axis. A similar decagonal phase in Al-20-at.%-Mn alloy reported by Bendersky can likewise be explained by the addition of mirror planes intersecting a fivefold axis of the icosahedral phase.