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The preparation and properties of Ba-Si-O-N glasses are reported. These oxynitride glasses were prepared by melting mixtures of BaH 2 , SiO 2 , and Si 3 N 4 powders in a nitrogen atmosphere at 1550°-1700°C. The glasses were characterized by X-ray powder diffraction, differential thermal analysis, and scanning electron microscopy. Final glass compositions were calculated from analyses obtained by energy dispersive X-ray (EDX) spectroscopy and combustion analysis, for cation and anion compositions, respectively. The glasses were found to be homogenous, translucent gray to opaque black, and consists of N contents of up to 42 equiv% and Ba contents of up to 36 equiv%. Determined glass densities varied between 3.27 and 4.18 g/cm 3 , and calculated molar volumes varied between 10.28 and 11.11 cm 3 /mol. Both density and molar volume increase with Ba content. Glass compactness (0.45-0.49), glass transition temperature (786°-905°C), and microhardness (7.93-9.56 GPa) were found to increase linearly with N content. The refractive index increased from 1.66 to 1.91 and was found to be strongly correlated with the amounts of Ba and N.

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