Lithium, Sodium, and Potassium Interdiffusion
in One-Alkali Glasses

T. A. Zykova

Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences,
ul. Odoevskogo 24/2, St. Petersburg, 199155 Russia

Received March 25, 1996

Abstract—The ion-exchange diffusion in one-alkali silicate glasses in the presence of concentration gradients
of two or three ions (Li⁺, Na⁺, and K⁺) was studied as a function of direction of the diffusing ion flux. It was
found that in the ternary systems, there are regions of the so-called ascending diffusion, where the direction of
increase in the flux density of sodium ions is opposite that of the gradient of glass-forming ion concentration
determined at the glass–molten salt interface. The ion diffusion in a glass was considered in terms of nonequi-
librium thermodynamics. An ion-exchanged glass layer was assumed to be a regular solid solution. The excess
free energies of formation of binary and ternary solid solutions in a glass were calculated. The concentration
distribution in an ion-exchanged glass layer was analyzed as a function of the thermodynamic properties of
components.

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