The mobility of Na+ in the glass was measured at 277 to 545C by using a 27Na tracer and monitoring the residual γ-ray activity. The data could be described by:

D (cm2/s) = 8.2 x 10-3 exp[-17.1(kcal/mol)/RT]

below the glass transition temperature, and by:

D (cm2/s) = 1.6 x 101 exp[-27.6(kcal/mol)/RT]

above the glass transition temperature.

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