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 index1–4; 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 families5–8, the formation of pure nitride glasses has not hitherto been demonstrated. Here we report the formation of glasses in the system Li3N-Ca3N2-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).