Vibrational spectra and structure of heavy metal oxide glasses

The infrared reflectance spectra at near-normal and off-normal incidence and polarized Raman spectra have been investigated to characterize the structure of PbO-Bi2O3-Ga2O3 glasses. Infrared reflectance bands at 400 cm(-1), 470 cm(-1) and 610 cm(-1) have been assigned to Pb-O, Bi-O and Ga-O related vibrations, respectively. The polarized Raman spectra were deconvoluted into seven bands which have been classified into four sets of modes: (1) depolarized low-frequency Raman modes at 30-70 cm(-1), (2) strongly polarized Pb and Bi heavy metal vibrations at 120 to 140 cm(-1); (3) polarized Ga-O-Pb, Ga-O-Bi, Bi-O-Pb, Ga-O-Ga and Bi-O-Bi bridging-oxygen modes at 300-600 cm(-1); (4) non-bridging oxygen modes at 600-700 cm(-1). The optic vibrations observed in the series of glasses indicate that most cations behave essentially as network-formers. The low-frequency Raman scattering was analyzed on the basis of Martin and Brenig's acoustic model, from which some intermediate range structural information is derived. The structural correlation and structural units which determine the high frequency modes in these glasses are discussed.