INFRARED AND RAMAN-SPECTRA OF LEAD FLUOROSILICATE GLASSES

The Raman (10-1200 cm-1) and infrared (90-2000 cm-1) spectra are reported for a series of lead fluorosilicate glasses having the composition (65-x)PbO-xPbF2-35SiO2, where x = 0, 10, 15, 20, and 25. The Pb-O band near 140 cm-1 in the Raman spectrum decreases in intensity with increasing PbF2 content. A new band appears in the Raman spectrum near 100 cm-1 and increases in intensity as PbF2 is added. In the far-infrared spectra, bands attributed to Si-O bending motions increase in frequency and decrease in width with increasing PbF2 content. These changes are explained as a result of the perturbation of the silicate structure by the presence of PbF2 and by the substitution of a fluorine for an oxygen atom in the PbO4 pyramidal units.