VIBRATIONAL-SPECTRA OF BISMUTH SILICATE-GLASSES AND HYDROGEN-INDUCED REDUCTION EFFECTS

Raman (10-1200 cm-1) and infrared reflectance (100-2000 cm-1) spectra are reported for bismuth silicate glasses of the formula xBi2O3.(10-x) SiO2 with x = 9, 8, 7, 6, 5, 4. The basic vibrational characteristics and the possible glass structure are discussed. The results provide ev idence that bismuth oxide behaves as the network former while silicon oxide is present as isolated SiO4 tetrahedra. Hydrogen treatment was p erformed at 300-degrees-C on a bismuth silicate glass with x = 5. The intensity of most Raman bands decreased with increasing exposure time. The infrared spectrum after reduction showed vibrational bands at 112 4 and 1220 cm-1 which are characteristic of Si-O-Si stretching vibrati onal modes in a fused-silica network. The spectral changes observed in dicate the formation of bismuth metallic colloids as well as the forma tion of the bridged Si-O-Si structure in the glass surface layer durin g reduction.