EFFECT OF HYDROXYL CONTENT ON PHASE-SEPARATION IN SODIUM-SILICATE GLASSES

The rate of phase separation in sodium silicate glasses increases as t he hydroxyl content increases. This ina ease occurs as an increase in the growth rate during the coarsening stage for glasses exhibiting nuc leation and growth. The rate of phase separation by spinodal decomposi tion increases due to enhanced diffusion with ina easing hydroxyl cont ent. There is no change in the miscibility limit with a doubling of th e hydroxyl concentration. Although a small change (3 K) in the spinoda l limit was found, it is uncertain if this result is significant.