The successive phase transformation in a Co-rich Al–Ni–Co decagonal phase

Abstract

Peak broadening and the peak positions of Bragg reflections were studied with the high-resolution X-ray diffraction method for decagonal Al 72.7Ni 8.5Co 18.8 quasicrystals. From the Q ⊥ dependences of the full-width at half-maximum (FWHM) of the Bragg reflections and the peak shifts from ideal Bragg peak positions along the longitudinal direction, these decagonal quasicrystals were classified into three groups with different phason strains. These three groups were identified as the random phason strain, the one-dimensional linear phason strain and the two-dimensional linear phason strain, respectively. This means that the Al 72.7Ni 8.5Co 18.8 decagonal phase undergoes a successive phase transformation from a decagonal quasicrystal through a one-dimensional quasicrystal to an approximant crystal.