Preparation and properties of mixed La-Pr silicate oxynitride glasses

The preparation and properties of mixed lanthanide (La, Pr) silicate oxynitride glasses are reported. These oxynitride glasses were prepared by melting mixtures of La, Pr, SiO₂ and Si₃N₄ powders in a nitrogen atmosphere at 1750 C. The glasses were characterized by X-ray powder diffraction, differential thermal analysis, scanning and transmission electron microscopy. Glass compositions were calculated from the 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, optically opaque black, and to contain contents up to 66 e/o of N and up to 48 e/o of La-Pr. The physical properties were found to vary linearly with the degree of substitution of La by the Pr. Determined glass density increases substantially upon the substitution of La by Pr, up to 5.49 g/cm³. The calculated molar volumes and compactness values decrease and increase respectively by the substitution of Pr for La. Glass transition temperatures and microhardness increase upon the substitution by Pr, up to 1086 C and 10.98 GPa, respectively. The refractive index increases upon the substitution by Pr up to 2.00.