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Oxygen Sites in Quaternary Ca-Na Aluminosilicate Classes : O-17 Solid-State NMR Study  

Sung, So-Young (School of Earth and Environmental Science, Seoul National University)
Lee, Sung-Keun (School of Earth and Environmental Science, Seoul National University)
Publication Information
Journal of the Mineralogical Society of Korea / v.19, no.4, 2006 , pp. 347-353 More about this Journal
Abstract
The atomic-nano scale structures of multi-component aluminosilicate glasses have not been well understood in spite of its implications fur dynamics and generation of magma in the natural system due to lack of suitable spectroscopic and scattering experiments. Here, we report O-17 MAS and isotropic projection of 3QMAS NMR spectra for quaternary Na-Ca silicate glasses $[(CaO)_x(Na_2O)_{1-x}]\;(A1_2O_3)_{0.5}(SiO_2)_6,\;CNAS)$ at 14.1 Tesla where atomic configurations around bridging oxygen (Si-O-Si, Si-O-Al) and non bridging oxygen (Na-O-Si, Ca-O-Si, (Na, Ca)-O-Si) are partially resolved. With increasing Na content, the fraction of Na-O-Si increases while those for bridging oxygens remain constant. The Na/Ca ratio apparently affects the peak widths of bridging oxygen peaks (e.g., Si-O-Si)) and thus the topological entropy as well as chemical shifts of the bridging oxygen peaks, implying that both BOs and NBOs are strongly interacting with network modifying cations The effect of cation field strength on the degree of Al-avoidance was also discussed.
Keywords
Quaternary aluminosilicate glasses; NMR; disorder;
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