A rapid new method was presented for the determination of the diffusion coefficient of Cs in borosilicate glass. By using low-energy ion-scattering techniques, the diffusion coefficient of Cs in such a glass was determined at temperatures ranging from 723 to 849K. When compared with the conventional diffusion-couple methods where diffusion had to be monitored over distances of the order of 105nm it was shown that, by using low-energy ion-scattering, accurate measurements could be made when diffusion occurred over distances of the order of only 10nm. Diffusion coefficients for Cs which were as low as 2.6 x 10-21m2/s were deduced from the measurements. These values were a factor of 106 smaller than those which had been measured by applying diffusion-couple methods to the same system, and were more than a factor of 10 smaller than the Cs diffusion coefficients in such glasses which had been determined by using other techniques. At high temperatures, the results of the various methods were in complete agreement.

W.C.A.N.Ceelen, J.P.Jacobs, H.H.Brongersma, E.G.F.Sengers, F.J.J.G.Janssen: Surface and Interface Analysis, 1995, 23[10], 712-6