Internal Friction of Ion‐Exchanged Li₂O.Al₂O₃.2SiO₂ Glass

Abstract

Fibers of Li,O.A1,O32Si0, glass were ion-exchanged for 1 to 300 min in a n NaN03 bath at 366°C. The internal friCtiQn and the Li and Na concentration profiles were measured. As Na progressively replaced Li, the alkali internal friction peak became smaller while a new peak (mixed-alkali peak) appeared and increased in magnitude. These changes in internal friction are similar to those that occur when a second alkali is added to glasses prepared by conventional melting. The magnitudes of both internal friction peaks in the ion-exchanged glass depended on the overall composition of the glass; that of the alkali peak depended on the composition of the unexchanged glass core, whereas that of the mixed-alkali peak depended on the composition of the exchanged layer on the glass surface. When the exchanged surface layer was dissolved, the original alkali peak was restored, and the mixed-alkali peak disappeared. Changing the alkali distribution did not affect the mixed-alkali peak much; however, it caused the alkali peak to shift to higher temperatures and become smaller. The height of the alkali peak can be used to determine the maximum depth of penetration of the second alkali.

Investigations of the local distortions and EPR parameters for Cu2+ in xNa2O‐(30–x)K2O‐70B2O3 (5 ≤ x ≤ 25 mol%) glasses

“…Furthermore, addition of two kinds of alkali in borate glasses (i.e., one alkali element is gradually replaced by another with the total alkali content unchanged) can lead to the important mixed alkali borate glasses with novel mixed alkali effect, for example, the nonlinear behaviors of various physical properties with the variation of alkali content . This effect is mainly relevant to the transferring behaviors of alkali ions such as electrical conductivity, ion diffusion, dielectric relaxation, and internal friction . In addition, some transition‐metal oxides (e.g., CuO) can be doped into the above mixed alkali borate glasses for the researches of local structural and optical properties arising from 3d electronic energy levels.…”