Some effects of OH groups on sodium silicate glasses

Glasses of various compositions in the Na₂O-SiO₂ system were prepared with different levels of OH concentration. Phase separation kinetics, thermal expansion, radiation induced optical absorption, and internal friction of these glasses were studied. The increase in OH content in these glasses was found to (a) enhance the rate of phase separation; (b) increase thermal expansion above the glass temperature and change the dilatometric softening temperature in a way that depends on microstructure; (c) increase the radiation induced optical absorption bands associated with positive hole centers and decrease those associated with electron trap centers; and, (d) decrease the low temperature alkali peak and increase the high temperature peak of internal friction. Structural changes responsible for the effect of very small amounts of OH on these properties are described. It is imperative to determine and consider OH content in the evaluation of properties which are so significantly affected by it --Abstract, page iii