Ordering Principles in Decagonal Al-Co-Ni Quasicrystals

Abstract

The discovery of quasicrystals has extended the traditional concept that crystalline matter is a periodic arrangement of identical units such as atoms or molecules. The typical quasicrystal is an intermetallic compound in which the building blocks are arranged in a non-periodic but highly ordered way. Of particular interest is the study of these ordering principles as a function of chemical composition and temperature in decagonal quasicrystals where periodic and aperiodic ordering even coexists in the same crystal structure. Structural information from diffraction experiments is the key for revealing these ordering principles and the prerequisite for a comprehensive study of the structure–property relationships. We present here the first all-inclusive in-situ high-temperature X-ray diffraction study of decagonal Al₇₀Co₁₂Ni₁₈, a stable quasicrystal with a wealth of diffraction phenomena.