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27 Al MAS NMR spectra of 12 fluoroaluminate crystals with known crystal structures and 40AlF 3 ·(20- x )BaF 2 · x BaCl 2 ·20CaF 2 ·17YF 3 ·3EuF 3 ·glasses ( x =0,3,6,9 and 12) in mol% were measured to examine the anion coordination environments around Al 3+ in the glasses. All the glasses gave NMR spectra with very similar line profiles, indicating that the anion coordination environments around Al 3+ are almost the same, and that only F − bonds to Al 3+ regardless of the substitution of Cl for F. A comparison of the isotropic chemical shift values and the line profiles between glasses and fluoroaluminate crystals concludes that only AlF 6 octahedra are present in the glasses and that these AlF 6 octahedra mainly build up chains and/or rings by sharing the two corners in cis -configuration. Moreover, fairly sharp and symmetric line-profiles in the glasses suggest considerably high symmetry in the F − -coordination around Al 3+ . |
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