Measurements of diffusion rates of Au in metal-metal and metal-metalloid glasses

Diffusion rates of Au in Ni_33.3Zr_66.7, Ni₆₄Zr₃₆, Fe₄₀Ni₄₀B₂₀ and Pd_77.5Cu₆Si_16.5 metallic glasses have been measured over a range of temperatures by a Rutherford α-particle backscattering technique. Experimental procedures and methods of analysis are described briefly and possibilities of experimental error are discussed. The measured diffusion rates obey Arrhenius relationships, yielding activation energies of approximately 2eV. Some diffusivity values measured for Fe₄₀Ni₄₀B₂₀ and Pd_77.5Cu₆Si_16.5 above the glass transition temperature, Tg, also lie on the same Arrhenius plots. In each alloy, pre-annealing of the glass has virtually no effect on the diffusivity or activation energy values. Diffusion rates of Au are between two and three orders of magnitude lower than the diffusion rates of a metalloid atom at the same temperatures in the same glass. At a given temperature, the diffusion rate of Au is lower in a glass of higher Tg. However, normalisation with Tg does not normalise the diffusivity values. Thus, at a given fraction of Tg, the diffusion rate is higher, in a glass with higher Tg.