Vibrational spectral analysis of structural modifications of Cr2O3 containing oxyfluoroborate glasses

Infrared and Raman spectra of oxyfluoroborate glasses of the compositions 20CaF2–20 ZnO–(60-x) B2O3-x Cr2O3 with 0 ≤ × ≤ 0.10 mol% (x = 0, 0.02, 0.04, 0.05, 0.06, 0.07, 0.08 and 0.1) have been analyzed in order to explain the role of Cr2O3 on the structure of these glasses. Density, molar volume, oxygen molar volume and oxygen packing density are determined to explain the packing of the atoms in the glasses. From these studies, the existence of different borate groups like di-, tri-, tetra-, penta-, ortho-, pyro- and metaborates in these glasses is established. With the increase in the concentration of Cr2O3 up to 0.06 mol%, conversion of BO3 units into BO4 units and above this mole fraction the reconversion of BO4 units into BO3 units is observed. The breaking and reforming of the boroxol ring is explained from the Raman spectral studies of these glasses.