Effect of Water Incorporation on the Diffusion of Sodium in an Alkaline-Earth
Boroaluminosilicate Glass¹

Lei Tian and Rüdiger Dieckmann

Department of Materials Science and Engineering, Cornell University, Bard Hall
Ithaca, NY 14853-1501, U.S.A.

Chung-Yuen Hui

Department of Theoretical and Applied Mechanics, Cornell University, Thurston Hall
Ithaca, NY 14853-1501, U.S.A.

J. Greg Couillard

Corning Incorporated
Corning, NY 14831, U.S.A.

Abstract

      Tracer diffusion coefficients of sodium ions diffusing in an alkaline-earth boroaluminosilicate glass¹ were measured by using Na-22 as a radioactive tracer. It was found that the presence of a significant amount of water vapor in the atmosphere surrounding a diffusion sample during diffusion annealing reduces considerably the mobility of sodium in the near-surface region of the glass. This partial immobilization of Na is attributed to an interaction between water dissolved into the glass and diffusing sodium ions.

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¹  Corning Code 1737 glass

Normalized Na-22 residual radioactivity profile from a sodium tracer diffusion experiment performed at 650 °C in wet air (= air saturated with water at 80 °C). The dashed line shown in the figure corresponds to the profile expected in the absence of any moisture in the environment during diffusion annealing. A(x=0) is the initial residual radioactivity and A(x) is the residual radioactivity after the removal of sample material with the thickness x. The experimental profile suggests that the diffusion of sodium in the near-surface region occurs significantly slower than in the bulk. The solid line corresponds to a fit of the equations derived in the paper to the experimental data.

(J. Non-Cryst. Solids, 296 (1-2) [2001] 123-134)

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