Sodium tracer diffusion in an alkaline-earth boroaluminosilicate glass

Sodium tracer diffusion coefficients, D∗Na, have been measured in an alkaline-earth boroaluminosilicate glass in the temperature range 500–800°C by using the radioactive isotope Na-22. It was found that the activation energy of the sodium tracer diffusion changes near the strain point (666°C). Therefore, two Arrhenius-type functions are needed to describe the temperature dependence of D∗Na in this temperature range. Below 664°C, D∗Na=10(−2.21±0.07) exp (−(129.9±1.2 kJ/mol)/RT) cm2/s and above 664∘C, D∗Na=10(−0.23±0.15) exp (−(165.5±3.0 kJ/mol)/RT) cm2/s.