Sodium tracer diffusion and 11B NMR study of glasses of the type (Na2O)0.17(B2O3)x(SiO2)0.83−x

Sodium tracer diffusion coefficients, DNa⁎, have been measured for sodium borosilicate glasses of the type (Na2O)0.17(B2O3)x(SiO2)0.83−x as a function of temperature and the composition parameter x. At constant temperature, the tracer diffusion coefficient of sodium decreases as x increases. The activation enthalpy derived from sodium tracer diffusion data for temperatures up to about 308 °C increases with increasing values of x from about 60 to 85 kJ/mol. The pre-exponential factor of the sodium tracer diffusion coefficient as a function of x varies by about one order of magnitude. Results of 11B NMR measurements performed to study variations of the structure of the investigated glasses with their composition indicate that the fraction of boron present in BO4 tetrahedra decreases with increasing values of x and also that the Si/B-ratio next to BO4 tetrahedra is always significantly larger than the overall Si/B-ratio in the glass.