Nitridation Of Mixed Alkali Phosphate Glasses

Mixed alkali lead phosphate glasses were nitrided by treatment in dry ammonia atmosphere between 650 and 750 deg C for periods from 2 to 40 hours. The nitrogen content of these glasses increased linearly with the temperature of the thermal treatment. For a fixed temperature, N2 content raised as a function of time tending towards a maximum level. Nitrogen incorporation provoked a smooth and linear decrease of thermal expansion coefficient while the glass transformation and dilatometric softening temperatures as well as the chemical resistance showed a linear nitrogen dependent increase.