The structure of lead oxide and natural silicate glasses: An FTIR and XPS study

The short-to medium-range structure of silicate glasses affects the physical and chemical properties of the glass. However, the structure of silicate glasses is not well constrained. This thesis examines the short-to-medium range structures that exist in a suite of PbO-SiO2 glasses using Fourier-transform infrared (FTIR) and X-Ray photoelectron spectroscopy (XPS) and a suite of aluminosilicate glasses using FTIR techniques.;The results of this study indicate that structure in theses silicate glasses consists of several, co-existing Si-O units. The systematic fitting of IR spectra provides information of the types and quantities of Si-O units in a wide range of silicate glasses. This technique is rapid, inexpensive and may be used for Fe-bearing samples. High resolution XPS data, combined with thermodynamic calculations, helps clarify the Si-O structures that may exist in these silicate glasses. The results from this research will help to understand the structural controls on the physical and chemical properties of both synthetic and natural glass systems.;Keywords: FTIR, XPS, silicate glass, aluminosilicate glass, glass structure.;A new systematic approach to the fitting of FTIR spectra of PbO-SiO 2 silicate glasses indicates the IR spectra are composed of individual bands related to specific Si-O unit vibrations. The changes in the FTIR spectra may be explained by changes in the relative proportions of the different Si-O units. Very high resolution XPS data also indicate that silicate glass structure consists of discrete Si-O units. The exceptional resolution of the XPS data allows us, for the first time, to unambiguously quantify the bridging-oxygen concentrations in the glass, and use thermodynamic calculations to predict the structures that may exist in the glass. The XPS data also indicate that there must be metal-bridging oxygen in all glasses. Finally, the FTIR band fitting approach is applied to a suite of geologically relevant aluminosilicate glasses. It is shown that a shoulder at ∼1220 cm-1 may be used to differentiate and characterize glasses with respect to the SiO 2 content. Also, the bands identified in the FTIR spectra of the aluminosilicate glasses may be assigned to specific Si-O unit vibrations. This is the first study to show that FTIR may be used to probe the structure of complex aluminosilicate glasses.