Removal of OH absorption bands due to pyrohydrolysis reactions in fluoride-containing borosilicate classes

The purpose of this study is to decrease and to remove OH ions and H2O in borosilicate glasses, Fluoride-containing borosilicate glasses followed by dry-air-bubbling showed the significant decrease of OH absorption bands around 3500 cm(-1). The decrease of OH absorption bands was elucidated by the use of pyrohydrolysis reactions in these glasses where fluoride ions react with OH ions or H2O during melting. The rates of the decrease of OH absorption bands substantially depend on high valence cations of fluorides. Particularly, the decrease rates of OH absorption coefficients were in the order of ZrF4-containing glass > AiF(3)-containing glass > ZnF2-containing glass. ZrF4-containing glass treated by drg-air-bubbling showed a good capability to remove OH absorption band. Fluoride-containing glasses showed the low flow point in comparison with fluoride-free glasses. (C) 1997 Academic Press.