The diffusivities of implanted radioactive 103Pd and 195Au in icosahedral quasi-crystals were measured, at temperatures of between 810 and 270C, by using a radio-tracer technique together with serial sectioning via high-precision grinding or ion-beam sputtering. It was found that the diffusion coefficients obeyed differing Arrhenius laws, above and below 450C (figure 1). Thus, while diffusion above this temperature was explicable in terms of a vacancy mechanism that reflected the heterogeneity of the icosahedral structure, diffusion below 450C was suggested to occur via a phason-assisted direct mechanism.

First Low-Temperature Radio-Tracer Studies of Diffusion in Icosahedral Quasi-Crystals R.Blüher, P.Scharwaechter, W.Frank, H.Kronmüller: Physical Review Letters, 1998, 80[5], 1014-7