Diffusion in ZrTiCuNiBe bulk glasses at temperatures around the glass transition

The diffusion coefficients of impurities in two glasses, Zr41Ti14Cu12.5Ni10 Be22.5 and Zr46.75Ti8.25Cu7.5Ni10Be27.5 were measured at temperatures aroun d the caloric glass transition temperature. They were determined for anneal ing 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 Arrhen ius relation. A larger effective activation energy is indicated above about 585 K than below for these impurities. No change was observed for the bigg er Al atoms. The temperature dependence of the diffusion jump time of the i mpurities is compared with that of the visco-elastic relaxation of the glas ses. From this comparison we suggest that the different activation energies at higher and lower temperatures indicate a change of the diffusion mechan ism. (C) 1999 Elsevier Science B.V. All rights reserved.