Titanium induced structural modifications in bismuth silicate glasses

摘要

Glass system with compositions xTiO_2·(60 - x)Bi_2O_3·40SiO_2 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 TiO_2 content whereas the glass transition temperature shows the reverse trend; indicating the increase in compactness of the glass structure with increase in TiO_2 content. The Raman and FTIR studies reveal that on addition of TiO_2, some of SiO_4 tetrahedra units with three non-bridging oxygens (NBOs) per silicon are converted into SiO_4 tetrahedral units with four NBO per silicon and number of network forming BiO_3 pyramidal units goes on decreasing and no BiO_3 pyramidal units are observed in glass composition with x = 20. Bismuth plays the role of network modifier with BiO_6 octahedral units for all the studied glass compositions. TiO_2 acts as network former with TiO_4 tetrahedral units in all the glass compositions having titanium besides acting as network modifier TiO_6 octahedral units in glass compositions with x = 10, 15 and 20. However, the glass composition with x = 15 has maximum number of TiO_4 structural units among all the studied glass compositions.