27Al MAS NMR study on anion coordination around Al3+ in AlF3-BaF2-BaCl2-CaF2-YF3-EuF3 glasses

27Al MAS NMR spectra of 12 fluoroaluminate crystals with known crystal structures and 40AlF3·(20-x)BaF2·xBaCl2·20CaF2·17YF3·3EuF3·glasses (x=0,3,6,9 and 12) in mol% were measured to examine the anion coordination environments around Al3+ in the glasses. All the glasses gave NMR spectra with very similar line profiles, indicating that the anion coordination environments around Al3+ are almost the same, and that only F− bonds to Al3+ 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 AlF6 octahedra are present in the glasses and that these AlF6 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 Al3+.