Sodium Tracer Diffusion in a Glass-Ceramic Containing Nano-Sized Spinel Crystals
Lei Tian 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 sodium have
been measured at temperatures between 400 and 800 °C in a
glass-ceramic containing nano-crystalline spinel by employing the radioactive
tracer Na-22. Diffusion profiles of Na-22 obtained in this two-phase glass-ceramic
can be evaluated very well by assuming a single tracer diffusion coefficient
for describing the diffusion on a macroscopic length scale. The values of the
tracer diffusion coefficients obtained range from 4·10-10 to 3·10-7 cm2/s.
A simple Arrhenius equation, D*Na = 10(-1.89±0.08)·exp(-(96.7±12.1 kJ/mol)/R·T) cm2/s, summarizes
the data very well. Based on the results from separate sodium tracer diffusion
experiments in spinel it is concluded that sodium ions diffuse practically only
in the silica-rich glass matrix of the glass-ceramic and that the dispersed
nano-sized spinel particles practically do not contribute to the diffusion of
sodium ions.
Arrhenius plot of sodium tracer
diffusion coefficients measured with the radioactive isotope Na-22 diffusing in
the glass-ceramic with nano-sized spinel inclusions.
(Journal of Non-Crystalline Solids, 281
(1-3) [2001] 55-60)