Synchrotron x-ray studies of phason and phonon strains in a Co-rich Al-Ni-Co decagonal quasicrystal

Peak broadening and peak shifts of Bragg reflections were studied with the synchrotron single-crystal X-ray diffraction method for an Al72.7Ni8.5Co18.8 decagonal quasicrystal classified as the 5f state. From the Q sub (perpendicular) and Q sub (parallel) dependences of the full width of half maximum (FWHM) of the Bragg reflections along the longitudinal direction, the coexistence of random phason strains with phonon strains was observed. High-resolution synchrotron X-ray measurements could present quantitative estimations of these strains. The value of the random phason strain component is 0.0054 ∼ τ-11. The asymmetrical broadening due to the phonon strain shows that the single crystal may be constructed with two kinds of grains that have A5D values of 0.6273 and 0.6265 nm. (author)