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A new approach to determine and quantify structural units in silicate glasses using micro-reflectance Fourier-Transform infrared spectroscopy

Department of Earth Sciences, The University of Western Ontario, London, Ontario N6A 5B7, Canada

Correspondence: ^* E-mail: kdalby{at}uwo.ca

Eight silicate unit vibrational modes were identified in a suite of PbO-SiO₂ glasses using micro-reflectance Fourier Transform infrared (µR-FTIR) spectra that were transformed using the Kramers-Kronig relation. The transformed FTIR spectra, in the 800–1200 cm^–1 range, were deconvolved systematically into eight Voigt-shaped bands at centers that were predicted from the second derivative of the spectra. The area of the eight bands varied as a function of SiO₂ content, and these trends were combined with theoretical constraints to identify and assign the bands to seven provisional silicate units: SiO^4–₄ (830 and 860 cm^–1), Si₂O^6–₇ (900 cm^–1), Si₆O^12–₁₈ (950 cm^–1), Si₂O^4–₆ (980 cm^–1), Si₄O^6–₁₁ (1010 cm^–1), Si₂O^2–₅ (1050 cm^–1), and SiO₂ (1100 cm^–1). The provisional units were then grouped according to their NBO/T values: NBO/T = 4 (SiO^4–₄), NBO/T = 3 (Si₂O^6–₇ ), NBO/T = 2 (Si₆O^12–₁₈ and Si₂O^4–₆ ), NBO/T = 1 (Si₄O^6–₁₁ and Si₂O^2–₅ ) and NBO/T = 0 (SiO₂). The derived quantities of each NBO/T unit compare favorably with nuclear magnetic resonance data for PbO-SiO₂ glasses reported in the literature. This new approach for determining glass structure is advantageous because it may be performed on small Fe-bearing samples with minimal preparation, and analyses are rapid and relatively inexpensive.

Key Words: IR spectroscopy • glass structure • band fitting • PbO-SiO₂

This article has been cited by other articles:

				C. D.M. Dufresne, P. L. King, M. D. Dyar, and K. N. Dalby Effect of SiO2, total FeO, Fe3+/Fe2+, and alkali elements in basaltic glasses on mid-infrared spectra American Mineralogist, November 1, 2009; 94(11-12): 1580 - 1590. [Abstract] [Full Text] [PDF]