Caesium diffusion in sodium borosilicate glass studied by low‐energy ion scattering

Abstract A new, time‐saving method to determine the diffusion coefficient of caesium in sodium borosilicate glass is presented. With low‐energy ion scattering (LEIS) the diffusion coefficient of caesium in this glass, where the main components are the same as those in nuclear waste glass, is determined in a wide temperature range (723–849 K). Compared to the conventional concentration couple method where the diffusion has to be studied over large distances (10 5 nm), it is shown that by using LEIS accurate measurements can be performed when diffusion takes place over distances of the order of 10 nm. Diffusion coefficients for caesium as low as 2.6 × 10 −22 m 2 s −1 are extracted from the measurements. This is a factor of 10 6 smaller than that measured with the concentration couple method for the same system and more than a factor of 10 smaller than diffusion coefficients for caesium determined in nuclear waste glasses by other techniques. At high temperatures the results of the different methods are in absolute agreement.