Sodium
Tracer Diffusion in Glasses of the Type (CaO∙Al2O3)x(2
SiO2)1−x
Hongxia Lu and Rüdiger Dieckmann
Department of Materials Science and Engineering,
Cornell University, Bard Hall, Ithaca, NY 14853-1501, U.S.A.
Abstract
Tracer
diffusion coefficients of the radioactive isotope Na-22 were measured in
glasses of the type (CaO·Al2O3)x(2SiO2)1−x to study the diffusion of sodium as a
function of glass composition, x, temperature and initial water content. The
diffusion of Na-22 in glasses diffusion-annealed in dry air can always be well
described by a single tracer diffusion coefficient, but sometimes not in
samples annealed in common air. It was found that the sodium tracer diffusion
coefficient decreases by about 6 orders of magnitude when the glass composition
x changes from 0 to 0.75 at 800 °C. The temperature dependence of the diffusion
of sodium seems to decrease as the silica content increases. Variations of the
initial water content in some of the glasses investigated did not very
significantly influence the rate of the tracer diffusion of sodium.
Composition dependence of the sodium tracer diffusion
coefficient, D*Na, for glasses of the type (CaO·Al2O3)x(2SiO2)1−x of Set I
at temperatures between 700 and 850 °C: a plot with lines obtained by fitting
an empirical equation of the type log D*Na = A + exp (−B·x + C) to the experimental data.
J. Non-Cryst. Solids, 353 (26) [2007]
2528-2544.