Nitrogen Dissolution in Sodium Alkaline-Earth Metaphosphate Melts

Phosphorus oxynitride glasses were prepared by remelting (5O – X )Na₂O · X BaO · 50P₂O₅, X = 0, 10, 20, 25, and 30, and 30Na₂O · 20MO · 50P₂O₅, M = Mg, Ca, Sr, and Ba', glasses in anhydrous ammonia. The nitrogen content depends upon the temperature and time of remelting in ammonia and the concentration and size of the alkaline-earth ion. Nitriding the starting glass decreased the dissolution rate in deionized water and thermal expansion coefficient and increased the dilatometric softening temperature and refractive index. The dissolution rate of the base glass in deionized water depended upon the concentration and size of the alkaline-earth ion, but for nitrided glasses, it was essentially independent of the alkaline-earth cation. The thermal expansion coefficient for all the oxynitride glasses decreased with increasing alkaline-earth concentration and cation field strength.