INFRARED-SPECTROSCOPY ON LEAD SILICATE GLASS

The reflectance spectra of some lead silicate glasses of general formula (PbO)x(SiO2)y have been measured in the infrared frequency range from 50 to 4000 cm-1. The dispersion and absorption spectra in the range 50-2000 cm-1 have been calculated from the reflectance data using the Kramers-Kronig relations. The band at approximately 135 cm-1 is assigned to the stretching vibration of lead-oxygen bonds. The shoulder band of the silicon-oxygen stretching mode at approximately 900 cm-1 shows a weak coupling of those bonds to the Pb2+ modifier. The vibration strength of those bands shows that the number of the Pb2+ modifier increases first up approximately to 50 Mol% with the increase of PbO content and then decreases rapidly. It indicates that different PbO content causes different structural forms in lead silicate glasses: The addition of small amounts of PbO to vitreous silica serves to modify the continuous three-dimensional silica network: whereas in those glasses with a high lead content, the influence of the cation, Pb2+, appears to lie between that of network former and network modifier. This result is in agreement with the structural model of Worrel and Henshall.