Nitride glasses obtained by high-pressure synthesis

THE incorporation of nitrogen in oxide glasses can lead to improved physical properties such as hardness and refractive index^1-4; one might accordingly expect to see a further improve-ment in glasses containing nitrogen as the only anion. But while there are now many examples of non-oxide glasses in the halide and chalcogenide families^5-8, the formation of pure nitride glasses has not hitherto been demonstrated. Here we report the formation of glasses in the system Li₃N-Ca₃N ₂-P₃N₅, by the rapid quenching of fused mixtures of the nitrides at high pressures. The use of high-pressure conditions prevents thermal decomposition of the nitride mixtures to gaseous nitrogen. The new nitride glasses are stable in air, have remarkably high refractive indices (1.97-2.0), hardness exceeding that of silica glass, and high glass transition tempera-tures (7g > 700°C).