Preparation of Na₂S-B₂O₃-SiO₂ glass systems and local structure analysis

Ternary alkali borosilicate glasses containing sulfur were prepared by conventional melt quenching method, and their chemical bonding states were investigated based on X-ray Photoelectron Spectroscopy (XPS) and ²⁹Si, ¹¹B Magic Angle Spinning (MAS)-Nuclear Magnetic Resonance (NMR) measurement. The glass samples changed in color from blue to reddish brown due to the remaining sulfur and their glass compositions. These phenomena is closely related with the glass structure. From S2p photoelectron spectra, it can be seen that the sulfur exists with a negative charge in the glass. The formation of non-bridging oxygen components was observed from O1s photoelectron spectra of the glasses, which colored to brown and reddish brown. Furthermore, the signal of silicon atoms coordinated to the sulfur was detected in these glasses by the ²⁹Si MAS-NMR measurement. From these results, it was considered that sulfur atoms bonded silicon atoms at the formation range of non-bridging oxygen component, and the bond of silicon to sulfur in the glasses caused the change in the sample coloration.