Diffusion in ZrTiCuNiBe bulk glasses at temperatures around the glass transition

The diffusion coefficients of impurities in two glasses, Zr(41)Ti(14)Cu(12.5)Ni(10)Be(22.5) and Zr(46.75)Ti(8.25)Cu(7.5)Ni(10)Be(27.5) were measured at temperatures around the caloric glass transition temperature. They were determined for annealing times during which there was no decomposition in either of the alloys. For Co, Fe and B the data could not be reasonably fitted by a single Arrhenius relation. A larger effective activation energy is indicated above about 585 K than below for these impurities. No change was observed for the bigger Al atoms. The temperature dependence of the diffusion jump time of the impurities is compared with that of the visco-elastic relaxation of the glasses. From this comparison we suggest that the different activation energies at higher and lower temperatures indicate a change of the diffusion mechanism. (C) 1999 Elsevier Science B.V. All rights reserved.