Tracer diffusion of thallium ion in glass

Tracer diffusion of thallium ion in borosilicate glass is performed in the temperature range 723-873 K. The diffusion coefficients were evaluated using the basic integral of Fick's second law of diffusion. The coefficient of Tl+ diffusion in glass followed the Arrhenius type equation. The observed high activation energy of diffusion is attributed to the large size of the diffusing species relative to that of the exchanging Na+ on K+ ions of the glass matrix. The accompanying change in entropy has a positive sign and the same is indicative of a certain degree of disorder during Tl+ diffusion. (author)