title: 93Nb and 17O NMR chemical shifts of niobiophosphate compounds.
abstract: Niobiophosphate compounds with a large range of niobium and oxygen environments were studied with (93)Nb and (17)O solid-state NMR. (93)Nb isotropic chemical shift of pure niobate Nb(ONb)(6), pure phosphate Nb(OP)(6) and mixed phosphate-niobate Nb(OP)(x)(ONb)((6-x)) (1<or= x<or=5) sites were measured at a high magnetic field (18.8T). (93)Nb chemical shifts were found to be sensitive to the variation of local charge on Nb, but not to the local bond geometry (i.e. crystallographic site and edge or corner connectivity). A systematic shift to high field of the (93)Nb chemical shift is measured when x increases. Then, (17)O NMR spectra of a series of enriched samples provided the chemical shift and quadrupolar parameters for 4 types of oxygen environment (P-O-P, P-O-Na, P-O-Nb and Nb-O-Nb). Finally, Nb-O-Nb sites were characterized by a large (17)O chemical shift anisotropy.
authors.affiliation: Unité de Catalyse et Chimie du Solide, UMR CNRS 8181, Ecole Nationale Supérieure de Chimie de Lille, Université des Sciences et Technologies de Lille, BP 108, 59652 Villeneuve d'Ascq Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Flambard
authors.forename: L
authors.initials: L
authors.lastname: Montagne
authors.forename: L
authors.initials: L
authors.lastname: Delevoye
authors.forename: S
authors.initials: S
authors.lastname: Steuernagel
mesh_terms: D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D009556:Niobium / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D010103:Oxygen Isotopes / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry*
chemical_list: D010103:Oxygen Isotopes; D010710:Phosphates; D009556:Niobium; D010100:Oxygen