Diffusion In Binary Geo2-Sio2 Glasses

The diffusion of germanium in GeO2-SiO2 glasses with up to 18 mol% GeO2 has been investigated by annealing of doped layers on the inner surface of quartz glass tubes between 1700 C and 2000 C in 1 bar oxygen atmosphere and measuring radial concentration profiles by x-ray microprobe analysis, subsequent to the tube collapse. By comparison with calculated profiles, diffusion coefficients could be determined and fitted by an Arrhenius function, where the pre-exponential D0=10 3.63cm2s-1 is constant but the activation energy decreases slightly with increasing concentration c(mol% GeO2) according to E=(590-1.4c)kJmol-1.