X-ray absorption near edge structure analysis of valence state and coordination geometry of Ti ions in borosilicate glasses

The effects of borosilicate glass composition and melting condition on valence state and coordination geometry of polyvalent Ti ions have been studied by X-ray absorption experiments. The results indicate that most of Ti3+ ions are oxidized into Ti4+ ions when Ti2O3 is doped into sodium borosilicate glasses. When TiO2 is doped into sodium borosilicate glasses, almost all of titanium ions are in the form of Ti4+. Doping both graphite and titanium oxide simultaneously in borosilicate glasses favors the formation of small amounts of Ti3+ ions. Ti4+ ions occupy both fivefold and sixfold coordinated sites in borosilicate glasses with non-bridging oxygen (NBS1), mainly fivefold coordinated sites. For borosilicate glasses without non-bridging oxygen (NBS2), Ti4+ ions are in both fourfold and fivefold coordinated sites. Using reducing agents during melting procedure favors the formation of fourfold coordinated Ti4+ ions in NBS2.