Relation Between Time and Temperature Dependence of Diffusion and the Structural State in ZrTiCuNiBe Bulk Glasses

Abstract

Time and temperature dependence of impurity diffusion is measured in detail for several ZrTiCuNiBe bulk glasses in a wide temperature range. We find that neither the quenched-in free volume nor a small volume fraction of crystals have a significant effect on the diffusivity. It is shown that the composition of these glasses has a much weaker effect on the diffusion coefficients than have structural changes of the glass. By long time relaxation the reversible metastable equilibrium of the glass structure could be reached at temperatures below the calorimetric glass transition. For this metastable equilibrium state a single set of diffusion parameters, activation enthalpy and pre-factor of the diffusion coefficient, is derived in the entire temperature range above and below the glass transition. This indicates that the usually observed non-linear Arrhenius behavior of diffusion coefficients in the ZrTiCuNiBe bulk glasses is caused by insufficient structural relaxation at temperatures below the calorimetric glass transition.