Ordering principles in decagonal Al-Co-Ni quasicrystals

The discovery of quasicrystals has extended the traditional concept that cr ystalline matter is a periodic arrangement of identical units such as atoms or molecules. The typical quasicrystal is an intermetallic compound in whi ch the building blocks are arranged in a non-periodic but highly ordered wa y. Of particular interest is the study of these ordering principles as a fu nction of chemical composition and temperature in decagonal quasicrystals w here periodic and aperiodic ordering even coexists in the same crystal stru cture. Structural information from diffraction experiments is the key for r evealing these ordering principles and the prerequisite for a comprehensive study of the structure-property relationships. We present here the first a ll-inclusive in-situ high-temperature X-ray diffraction study of decagonal Al70Co12Ni18, a stable quasicrystal with a wealth of diffraction phenomena.