Phonon scattering in quasicrystalline i-Al72Pd19.5Mn8.5: A study of the low-temperature thermal conductivity

We measured the thermal conductivity of an icosahedral quasicrystal i-Al72Pd19.5Mn8.5 in the temperature range between 0.4 K and 300 K. The analysis of the low-temperature results was based on a Debye-type model. The results of the analysis for the two temperature regions of 0.4 K < T < 40 K and 0.4 K < T < 1 K, are not consistent in the sense that a tunnelling-states contribution to phonon scattering is verified only for 0.4 K < T < 1 K. The same fitting procedure indicates that structural defects of the stacking-fault type are an important source of phonon scattering. Their physical presence was clearly identified by a transmission electron microscopy experiment.