Complex metallic alloys in the Ce–Au–Sn system: a study of the atomic and electronicstructures

Abstract

We report the formation of a new stable quasicrystal approximantin the Ce–Au–Sn system. The crystalline structure of theCe15Au65Sn20 compound is investigated by x-ray diffraction and is found to be of similar structure type to theZn17Sc3 1/1 approximant. Large clusters with icosahedral symmetry arelocated at the node of the body-centred cubic (bcc) unit cell(a = 1.5190 nm) containing 161 atoms. We have used transmission electron microscopy toemphasize the relationship of this new compound with the icosahedral spacegroup. The valence band has been investigated by photoemission spectroscopyand shows an indication of Van Hove singularities in the density of states,characteristic of quasicrystalline and related approximant phases. We expect similar1/1 approximant and possibly icosahedral phases to be discovered in the new RE–Au–Snsystems (where RE is rare earth). We also found a hexagonal phase with a large unit cellpossessing local icosahedral order, co-existing as a minority phase.