Average single bond strength and optical basicity of Bi2O3–B2O3 and Sb2O3–B2O3 glasses

Single bond strengths have been proposed of Bi–O bond equal to 102.5 kJ/mol in BiO6 group and of Sb–O bond equal to 229 kJ/mol in SbO3 group. Equations for calculation of average single bond strength BM–O of Bi2O3–B2O3 and Sb2O3–B2O3 glasses have been suggested taking into account the contribution of different structural units namely BiO6, SbO3, BO3 and BO4 groups. It has been found that the BM–O of Bi2O3–B2O3 and Sb2O3–B2O3 glasses decreases with increasing Bi2O3 or Sb2O3 content up to 233 kJ/mol at 65 mol% Bi2O3 and up to 256 kJ/mol at 90 mol% Sb2O3. The observed increase of refractive index based optical basicity Λ(no) with decreasing BM–O of Bi2O3–B2O3 and Sb2O3–B2O3 glasses has been discussed with increase the number of Bi–O–B, Sb–O–B, Bi–O–Bi and Sb–O–Sb chemical bonds containing oxide ions with increased polarizability in the glass structure. It has been discussed that high refractive index glasses with high optical basicity and weak chemical bonds are promising materials for application as components of non-linear optical devices.