Probing oxygen motion in disordered anionic conductors with 17O and 51V MAS NMR spectroscopy

Identification of the local environments of the ions in a solid-state electrolyte that contribute to the ionic conductivity or remain trapped in the lattice represents a challenge for many experimental probes of structure. We show that high-resolution O-17 magic angle spinning nuclear magnetic resonance (MAS NMR) spectra may be obtained even from the highly disordered, layered materials alpha-Bi4V2O11 and beta-Bi4V1.7Ti0.3O10.85, in which the different oxide sites in the lattice may be distinguished. The sites responsible for anionic conduction were determined directly from the variable-temperature O-17 NMR spectra, and correlation times for motion were estimated. Double-resonance O-17/V-51 NMR methods were used as confirmation of the assignments of the resonances and as a second experimental probe of motion that is sensitive to mobility involving oxide ion hops between the same crystallographic sites.