X-ray diffraction study of a phason strain in an Al-Cu-Fe icosahedral quasicrystal

Abstract

Detailed examinations of the peak profiles and the positions of the Bragg peaks are carried out with the X-ray diffractometer for single-grain samples of the Al—Cu—Fe icosahedral quasicrystal. Notable peak shifts from the ideal positions with linear Q⊥ dependence are observed along the fivefold directions. This means that the sample contains linear phason strain. The amplitude of the linear phason strain is estimated as—0.0543, which is close to a theoretical value for the phason-strain-inducing transformation from the icosahedral phase to the pentagonal phase (P2 phase), —1/τ⁶. The two-dimensional intensity distributions around the Bragg peaks on the twofold, threefold and fivefold axes are interpreted as consequences of the phason-strain-inducing pentagonal deformation.