Internal Friction of an Ag–In–Yb Icosahedral Quasicrystal

Abstract

Internal friction has been measured for an Ag–In–Yb Tsai-type icosahedral (i-) quasicrystal to investigate an energy-dissipation mechanism by phason relaxation, possibly operating in quasicrystals. A fairly large peak of the magnitude Q⁻¹ ≈ 0.022 was observed, which was shown to be of the thermally-activated relaxation type. The frequency factor and activation enthalpy were evaluated to be 10²⁰ s⁻¹ and 2.6 × 10⁻¹⁹ J (1.6 eV), respectively. The observed peak was analyzed on the assumption that it is of phason-origin. The magnitude of the phonon-phason coupling constant was estimated to be 0.008μ (μ: shear modulus), based on the model of the phonon-phason elastodynamics previously proposed. This value is comparable to those previously reported for Mackay-type i-phases such as i-Al–Pd–Mn and i-Al–Cu–Fe.