Fused silica doped with both Tb and Eu exhibited a visible fluorescent green band under ultra-violet light after heat treatment above 700C in a hydrogen atmosphere. The growth kinetics of the band were studied as a function of time, temperature and hydrogen pressure at 700 to 1050C, and were attributed to a hydrogen diffusion-controlled reaction. From these measurements, and using T, diffusion coefficients were evaluated. At 850 to 1040C, they were described by:

D(cm2/s) = 6.5 x 10-5 exp[-12.5(kcal/mol)/RT]

E.A.Weaver, R.W.Heckman, E.L.Williams: The Journal of Chemical Physics, 1967, 47[12], 4891-5