SURFACE NITRIDATION OF A PHOSPHATE-GLASS

Phosphate glass surfaces were nitrided by reacting them in dry ammonia at temperatures near the glass transition temperature (Tg) for up to 100 h. These treatments have significant effects on surface dependent glass properties. For example, the dissolution rate of a sodium-barium phosphate glass (Tg = 345°C) decreased by over an order of magnitude after 24 h in ammonia at Tg. X-ray photoelectron spectroscopic (XPS) analyses show that nitrogen in chemically incorporated into the glass structure at levels up to 3-5 at.%. Elemental depth profiles, obtained by XPS (for N) and by elastic recoil detection (ERD) analyses (for N and H), indicate that the surface oxynitrile layer extends to about 1 μm in depth. XPS analyses of in situ treated samples reveals the presence of several nitrogen species which affect the surface dependent properties by increasing the structural crosslink density of the glass surface. © 1990.