Expectations of increased stability for trapped electrons in high‐alkali glasses, based on extrapolations from observations on low‐alkali borate glasses, are not borne out. In 69Na2O‐31B2O3 glass, electron centers have approximately the same thermal stability as in Na2O·2B2O3 glass. In Na2Oplus;P2O5 glasses the lifetimes, 3 · 0.5 μS, of transiently trapped electrons as well as their absorption spectra prove to be independent of increase of Na2O content from 50 to 60 mol%. The same composition change destabilizes “permanent” hole centers. Exchange of Na2O with K2O in the metaphosphate glass also has no effect on the trapped electron lifetime. Small linear shifts in the trapped‐hole absorption peak wavelengths are observed in the latter case. The most important positive finding in the phosphate glasses is a pronounced mixed‐alkali effect on the yield of transiently trapped electrons and holes and of permanently trapped holes. The yield is a minimum at Na:K=1:1, due either to the elimination of trap sites or to the reduction of alkali ion mobilities which play a role in trap formation.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of the American Ceramic Society|
|State||Published - Mar 1981|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry