The mobility of Na+ in the glass was measured at 277 to 545C by using the 22Na tracer and monitoring the residual γ-ray activity. It was found that the diffusion could be described by:

D (cm2/s)  = 8.2 x 10-3 exp[-71.6(kJ/mol)/RT]

at temperatures below the glass transition temperature, and by:

D (cm2/s)  = 1.6 x 101 exp[-116(kJ/mol)/RT]

at temperatures above the glass transition temperature.

C.Kaps: Journal of Solid State Physics, 1984, 65[1], 189-92