Selective substitution of alkali cations in mixed alkali glass by solid-state electrochemistry

Electrosubstitution of alkali cations in mixed-alkali glass containing both Na2O and K2O for other monovalent metal cations (M+ = Li+, Ag+, and Cs+) was investigated using a solid-state electrochemical method. The fundamental electrolysis system consists of anode/M+-conducting microclectrode/glass/Na-beta-Al2O3/cathode, where M+ is substituted for the alkali metal ions in the glass under an applied electric field. Li+ ions attacked only Na+ sites, and Ag+ ions replaced Na+ sites more readily than K+. In contrast, Cs+ ions simultaneously substituted for both Na+ and K+ sites. The substitution behavior appears to depend on the difference in ionic conductivity between K+ and Na+ and the radius of the dopant. This mechanism was discussed qualitatively. (C) 2003 Elsevier Inc. All rights reserved.