Group optical basicity and single bond strength of oxide glasses

This paper is a review of our recent results in the field of group optical basicity of the oxide glasses. Dimitrov and Komatsu have recently introduced the concept of group (i.e. microscopic) optical basicity, proposed by Duffy and Ingram, to binary R₂O (RO) – TeO₂ (R = Na, Mg, Sr, Ba, Zn and Pb) and ternary 10R₂O.10R'O.80TeO₂ (R = Li, Na and K, R'= Mg, Ba and Zn) tellurite glasses based on N4 and N3 fractions of different TeO₄ and TeO₃ groups. In fact, the group basicity of TeO₄ unit with one non-bridging oxygen (λTeO_4⁻= 1.23), TeO4 unit without non-bridging oxygen (λTeO_4⁰= 0.99) and a terminal TeO₃ unit with two non-bridging oxygens (λTeO_3⁻= 0.82) is evaluated. Equations for evaluation of the theoretical optical basicity Λ_th(1) of Na₂O-B₂O₃, PbO-B₂O₃, Na2O-SiO2 and R₂O-RO-TeO₂ glasses are advanced taking into account the contribution of the mole fraction and the group basicity of different structural units, namely BO3, BO4 and SiO4 groups.Equations providing the calculation of the average single bond strength B_M-O of Na₂O-B₂O₃, PbO-B₂O₃, Na₂O-GeO₂, Bi₂O₃-B₂O₃ and ZnO-Bi₂O₃-B₂O₃ glasses are suggested considering the mole fractions of BO₃, BO₄, GeO₄, GeO₆, PbO₃, PbO₄ and PbO₆ groups.It is established that there is a general trend of optical basicity increase along with single bond strength decrease in borate-silicate-germanate-tellurite-bismuthate glasses sequence.Keywords: oxide glasses, optical basicity, bond strength, structure.