Ultraslow Li Exchange Processes in Diamagnetic Li2ZrO3 As Monitored by EXSY NMR

Two-dimensional (2D) Li-6 exchange magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy was used to probe extremely slow lithium hopping processes in a polycrystalline powder sample of lithium zirconate, Li2ZrO3. In agreement with the crystal structure of Li2ZrO3, the Li-6 MAS NMR spectra recorded are composed of two signals (- 0.10 and 0.26 ppm) with equal intensity. They reflect the two magnetically (and electrically) inequivalent Li sites in Li2ZrO3. The mixing-time dependent 2D MAS NMR spectra, which were acquired at a bearing gas temperature of ca. 310 K, clearly reveal off-diagonal intensities indicating Li exchange processes with exchange rates as low as 60 jumps/hour. To our knowledge, this is by far one of the slowest Li solid-state diffusion processes ever probed by Li-6 2D exchange MAS NMR spectroscopy (submitted to J. Phys. Chem. C, 2013).