Sodium tracer diffusion in glasses of the type (Na2O)0.2[(BO1.5)x(SiO2)1 − x]0.8

► Diffusion of Na-22 in sodium borosilicate glasses studied. ► Composition and temperature dependences of diffusivity determined. ► Activation energies, pre-exponential factor and Haven-ratio analyzed. ► Investigated whether take-up of water influences the diffusion of sodium.