Chemical order in an Al-Pd-Mn icosahedral quasicrystal

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Abstract
The icosahedral structure of A170 Pd20 Mn10 and A165Cu20Fe15 quasicrystals in rapidly solidified and annealed states has been examined by electron and X-ray diffraction techniques. Broadening and distortion of the diffraction peaks due to atomic disordering were observed in rapidly solidified A165Cu20Fe15, but were not observed in rapidly solidified A170Pd20Mn10. The rapidly solidified A170Pd20Mn10 quasicrystal has a highly ordered atomic arrangement which is nearly the same as that for an Al65Cu20Fe15 quasicrystal annealed at a temperature just below the melting point. On the basis of the thermodynamical data, it is presumed that a strong chemical order(bonding) between Pd and Al or Mn prevents the A170Pd20Mn10 quasicrystal from generating atomic disordering and phason strains during rapid solidification.