Studies on the characterization of sulfur and coloration in borosilicate glasses

Ternary alkali borosilicate glasses containing sulfur were prepared by a conventional melt quenching method, and their chemical bonding states were investigated based on XPS and ²⁹Si,¹¹B MAS-NMR measurement. The glass samples changed in color from blue to reddish brown due to the state of the sulfur and their glass compositions. From S2p photoelectron spectra, it can be seen that the sulfur exists with a negative charge in the glass. The forming of non-bridging oxygen components was observed from O1s photoelectron spectra of the glasses, which colored to brown and reddish brown. Furthermore, a signal from silicon atoms coordinated to the sulfur was detected in these glasses by the ²⁹Si MAS-NMR measurement. From these results, it is considered that sulfur atoms bonded silicon atoms at the forming range of the non-bridging oxygen component.