Probing Oxygen Motion in Disordered Anionic Conductors with 17 O and 51 V MAS NMR Spectroscopy

Abstract

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 ¹⁷ O magic angle spinning nuclear magnetic resonance (MAS NMR) spectra may be obtained even from the highly disordered, layered materials α-Bi ₄ V ₂ O ₁₁ and γ-Bi ₄ V _1.7 Ti _0.3 O _10.85 , 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 ¹⁷ O NMR spectra, and correlation times for motion were estimated. Double-resonance ¹⁷ O/ ⁵¹ V 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.