VIBRATIONAL-SPECTRA AND STRUCTURE OF HEAVY-METAL OXIDE GLASSES

The infrared reflectance spectra at near-normal and off-normal inciden ce and polarized Raman spectra have been investigated to characterize the structure of PbO-Bi2O3-Ga2O3 glasses. Infrared reflectance bands a t 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 spec tra were deconvoluted into seven bands which have been classified into four sets of modes: (1) depolarized low-frequency Raman modes at 30-7 0 cm(-1), (2) strongly polarized Pb and Bi heavy metal vibrations at 1 20 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 oxy gen modes at 600-700 cm(-1). The optic vibrations observed in the seri es 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 r ange structural information is derived. The structural correlation and structural units which determine the high frequency modes in these gl asses are discussed.