The role of TiO2 in the B2O3-Na2O-PbO-Al2O3 glass system

Optical and vibrational studies have been carried out on 60B2O3.(20-x)Na2O.10PbO.10Al2O3:xTiO2 (x=0, 1, 2, 3, 4, and 5 mol%) glasses, in order to understand the role of TiO2 in the 60B2O3.20Na2O.10PbO.10Al2O3 glass matrix. The X-ray patterns reveal homogeneous glasses over the entire compositional range. The absorption spectra show that the energy of the optical band gap (ΔEopt) and Urbach's energy (EU) decreases as TiO2 content increases. The changes observed in the Raman and IR spectra are related to the BO4→BO3 back conversion effect and the appearance of 'loose' BO4- groups. The data indicate that titanium ions act as a network modifier. - Graphical abstract: Behavior of the relative integrated intensity of the IR bands, Ar=A4/A3, as TiO2 content increases. A decrease of 45% of Ar indicates that the number of BO4 groups is decreasing due to the BO4→BO3 back conversion. Highlights: → The XRD data show the amorphous character of all measured glasses. → The optical absorption results evidenced possible change of the glass structure. → The Raman data have revealed some vibrational modifications. → The overall results indicate that titanium acts as a network modifier.