NITRIDE GLASSES OBTAINED BY HIGH-PRESSURE SYNTHESIS

THE incorporation of nitrogen in oxide glasses can lead to improved ph ysical properties such as hardness and refractive index(1-4); one migh t accordingly expect to see a further improvement in glasses containin g 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 f ormation of pure nitride glasses has not hitherto been demonstrated. H ere we report the formation of glasses in the system Li3N-Ca3N2-P3N5, by the rapid quenching of fused mixtures of the nitrides at high press ures. The use of high-pressure conditions prevents thermal decompositi on of the nitride mixtures to gaseous nitrogen. The new nitride glasse s are stable in air, have remarkably high refractive indices (1.97-2.0 ), hardness exceeding that of silica glass, and high glass transition temperatures (T-g > 700 degrees C).