Abstract
The diffusion of sodium ions in Type I silica glass was studied experimentally by using Na-22 as a radioactive tracer at temperatures between 400°C and 700°C. It was found that the sodium tracer diffusion coefficient in as-received glass was well described by an Arrhenius equation. All residual radioactivity profiles observed after pre-annealing glass samples in common and wet air at temperatures between 900°C and 1100°C and performing diffusion anneals at 650°C cannot be described by a single diffusion coefficient. A strong residual radioactivity decrease occurred near the surface, which was followed by a much smaller decrease in the bulk below. This type of profile was attributed to the generation of a near-surface region with a reduced sodium mobility during the pre-annealing. A mathematical model for the analysis of the observed profiles was developed and used to determine sodium tracer diffusion coefficients in the near-surface region and in the bulk. It was found that the sodium tracer diffusion coefficient in the near-surface region was by about two orders of magnitude smaller than that in the bulk. This immobilization of Na is believed to be due to a water-induced structural relaxation in the near-surface region during pre-annealing.
Original language | English |
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Pages (from-to) | 146-161 |
Number of pages | 16 |
Journal | Journal of Non-Crystalline Solids |
Volume | 286 |
Issue number | 3 |
DOIs | |
Publication status | Published - 2001 Jul 1 |
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry