Addition effect of SnO in optical property of Bi₂ O₃ -containing aluminoborate glass

We have found that an addition of SnO in a bismuth-containing aluminoborate glass, (CaO- B₂ O₃ - Bi₂ O₃ - Al₂ O₃ - TiO₂) (CaBBAT), decreases both the optical absorption coefficient in the visible region and the relative intensity of x-ray photoelectron spectroscopy (XPS) signal at 157 eV. Since signal intensity of electron spin resonance (ESR) at g=1.95 also decreased with increasing amount of SnO, it is suggested that bismuth radical-like species exist in the glass and that SnO reacts with the bismuth species. Concentration dependence of SnO in the XPS and in the ESR spectra shows that we can assign the observed signal to bismuth radical species in the glass. We, therefore, conclude that there is qualitative correlation between the optical absorption in the visible region and bismuth radical species in the CaBBAT glass.