31P MAS NMR spectroscopy with 93Nb decoupling and DFT calculations: A structural characterization of defects in a niobium-phosphate phase

Guillaume Girard (1) , Filipe Vasconcelos (1) , Lionel Montagne (1) , Laurent Delevoye (1)

1 UCCS - Unité de Catalyse et Chimie du Solide - UMR 8181

The present study has investigated the structure of four niobium phosphates compounds using 31P MAS NMR spectroscopy. Niobium 93Nb decoupling, applied during 31P NMR acquisition led to a resolution enhancement by a factor of 2–3, which allowed distinguish phosphorous sites separated by 1 ppm or less. The assignment of 31P spectra has been completed by use of first-principles calculations derived from the original XRD structures. One of the compounds, Na3.04Nb7P4O29, contains a sodium vacancy, clearly revealed in the 31P MAS spectrum obtained with 93Nb decoupling. A series of structural models were proposed to account for the sodium distribution in the structure of Na3.04Nb7P4O29 and the assignment was possible using DFT calculation and a statistical analysis of the NMR parameters.

Domaines: Matériaux

Guillaume Girard, Filipe Vasconcelos, Lionel Montagne, Laurent Delevoye. 31P MAS NMR spectroscopy with 93Nb decoupling and DFT calculations: A structural characterization of defects in a niobium-phosphate phase. Solid State Nuclear Magnetic Resonance, 2017, 84, pp.210-215. ⟨10.1016/j.ssnmr.2017.05.003⟩. ⟨hal-01969855⟩