Effect of Ag₂O addition on structural and optical characteristics of B₂O₃–Bi₂O₃–Na₂O–Nb₂O₅ oxide glass

In this work, bismuth-niobium based sodium borate glass was modified by introducing Ag₂O additives according to the formula 100 wt% {60 mol% B₂O₃ + 17.5 mol% Na₂O + 17.5 Bi₂O₃ + 5 mol%Nb₂O₅} + x wt% Ag₂O, where x = 0, 1.5, 3.0, 4.5, and 6.0. Glass samples were prepared by traditional melt quenching method, and silver oxide was incorporated by weight addition. X-ray diffraction analysis revealed the amorphous nature of the studied materials and that the addition of Ag₂O didn't affect structural phases. Vibrational transitions showed cross-linking between BO₃, BO₄, and BiO₃ structural groups, meanwhile the Na⁺, NbO₆, and BiO₆, in addition to the Ag²⁺ occupy the interstitial spaces. Furthermore, the study shows a transition of Bi₂O₃ from acting as a glass network modifier BiO₆ to a glass network former BiO₃. Study of the electronic transitions showed that the optical absorption edge is located around 505 nm. Furthermore, the addition of Ag₂O caused a slight decrease in the value of Urbach energy which means an increase in the structural ordering, that may be assigned to the conversion of BO₄ to BO₃.