title: Local structure of magnesium in silicate glasses: a 25Mg 3QMAS NMR study.
abstract: We have reported the 25Mg triple-quantum magic-angle spinning (3QMAS) NMR spectra of silicate glasses. The two-dimensional spectra suggest that the magnesium ions in MgSiO3, CaMgSi2O6, Ca2MgSi2O7, Mg3Al2Si3O12, and Li2MgSi2O6 glasses are mainly in octahedral environments, although in Na2MgSi2O6, K2MgSi2O6, and K2MgSi5O12 glasses they form tetrahedral species. We discussed the coordination environments of Mg based on the field strength of competing Mg2+, Ca2+, Na+, K+, and Li+ cations, and convincingly demonstrated that there is a correlation between them. These results indicate that the two-dimensional NMR spectroscopy such as MQMAS technique is a very useful method to analyze the local environments of nonframework cations in noncrystalline solids.
authors.affiliation: Institute for Study of the Earth's Interior, Okayama University, Misasa, Tottori, Japan. kshimoda@misasa.okayama-u.ac.jp
authors.forename: Keiji
authors.initials: K
authors.lastname: Shimoda
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nemoto
authors.forename: Koji
authors.initials: K
authors.lastname: Saito
mesh_terms: D005898:Glass / Q000737:chemistry; D007554:Isotopes / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D011789:Quantum Theory; D012015:Reference Standards; D017640:Silicates / Q000737:chemistry*
chemical_list: D007554:Isotopes; D017640:Silicates; D008274:Magnesium