Preparation and characterization of invert glasses with high CdO content

Abstract

Glasses from the binary CdO-B2O3 system were prepared with extended invert compositions containing high CdO content (50–90 mol%) by melting followed by annealing technique. Combined optical and FTIR spectral measurements were carried out to find out the structural constitution of the studied invert glasses and their suitability in optical purposes. Optical spectral data reveal distinct UV absorption due to unavoidable trace iron impurities. FTIR spectra indicate the role of CdO to convert some BO3 to BO4 groups as many of alkali and alkaline earth oxides. The IR spectra reveal distinct vibrational peaks due to BO3 and BO4 units within their specific different wavenumbers. At high CdO, the IR spectra reveal the possible sharing of vibrational peaks due to Cd-O, Cd-O-B or CdO4 as evidenced by the reference IR for crystalline CdO. Thermal expansion and density measurements show some changes which can be related to suggested behavior of Cd2+ ions. With high percent, CdO is assumed to behave as modifier beside forming CdO4 groups. The change in the role of CdO is also assumed to explain the variations in both the density and thermal expansion data. Such observed changes in both the density and thermal expansion are quite different than the borate anomaly identified in the thermal expansion data of alkali borate glasses and are identified at high CdO content.