Tracer diffusion coefficients were measured at 500 to 800C in the alkaline-earth boroaluminosilicate glass by using the radioactive isotope 22Na. It was found that the activation energy for Na tracer diffusion changed near to the strain point (666C). Two Arrhenius-type functions were therefore needed in order to describe the temperature dependence. It was found that, below 664C, the data could be described by:

D (cm2/s) = 6.2 x 10-3 exp[-129.9(kJ/mol)/RT]

The data above 664C could be described by:

D (cm2/s) = 5.9 x 10-1 exp[-165.5(kJ/mol)/RT]

Sodium Tracer Diffusion in an Alkaline-Earth Boroaluminosilicate Glass. L.Tian, R.Dieckmann: Journal of Non-Crystalline Solids, 2000, 265[1-2], 36-40