Titanium induced structural modifications in bismuth silicate glasses

Glass system with compositions xTiO2·(60 − x)Bi2O3·40SiO2 has been prepared by standard melt quench technique. The amorphous nature of the glass samples has been ascertained by the X-ray diffraction. It is observed that density and molar volume of the studied glasses decrease with increase in TiO2 content whereas the glass transition temperature shows the reverse trend; indicating the increase in compactness of the glass structure with increase in TiO2 content. The Raman and FTIR studies reveal that on addition of TiO2, some of SiO4 tetrahedra units with three non-bridging oxygens (NBOs) per silicon are converted into SiO4 tetrahedral units with four NBO per silicon and number of network forming BiO3 pyramidal units goes on decreasing and no BiO3 pyramidal units are observed in glass composition with x = 20. Bismuth plays the role of network modifier with BiO6 octahedral units for all the studied glass compositions. TiO2 acts as network former with TiO4 tetrahedral units in all the glass compositions having titanium besides acting as network modifier TiO6 octahedral units in glass compositions with x = 10, 15 and 20. However, the glass composition with x = 15 has maximum number of TiO4 structural units among all the studied glass compositions.