Study of Al surface segregation in icosahedral Al_62Cu_25.5Fe_12.5

摘要

Surface segregation of aluminium was observed during oxidation experiments of icosahedral Al_62Cu_25.5Fe_12.5,performed in-situ and at different temeprturs in the ultra-high vacuum chamber of a scannign Auger electron spectrometer.two regimes,below and above 770k,were observed in relation with severe segregation of Al atoms at the surface for T> 770K.We postulate that this temeprature dependent segregation rate is representative of the aluminium transport towards the surface of the quasicrystal.By analogy with classical diffusion experiments,we can thus determine reasonable estimates of the activation energy for Al self-diffusion in this quasicrystal.The results are consistent with the existence of phason flips below 770K and thermal vacancies above this temperature.