RDF analysis, positron annihilation and Raman spectroscopy of xTiO2–(60 − x)SiO2–40Na2O non-linear optical glasses: III. Non-bridging oxygen bonds tracing and structure analysis

xTiO2–(60 − x)SiO2–40Na2O glasses have proven an interesting linear and non-linear optical properties [M. Abdel-Baki, F. Abdel Wahab, F. El-Diasty, Mater. Chem. Phys. 96 (2006) 201]. The investigated glasses show one order of magnitude enhancement for the second-order index of refraction and third-order optical susceptibility over some TiO2 silicate glasses. In this work, we continue studying these glasses using three different techniques to analyze the glass structures seeking to provide a deep insight for the relation between structure, compositions and the optical characteristics of these glasses. Radial Distribution Function analysis (RDF) combined Raman spectroscopy are used to study these glasses. Positron annihilation lifetime spectroscopy and Doppler broadening measurements are carried out to investigate the change in the glass structure as the incorporation of TiO2 concentration into glass. The origin of the non-bridging oxygen (NBO) bonds has been traced to correlate their existence with the measured non-linear optical properties of the investigated glasses.