Na+ ion motion in Na3−xRu4O9: an NMR study of 23Na line shape

23Na nuclear magnetic resonance (NMR) line shapes have been measured over the temperature range from 125 K to 909 K to investigate Na+ ion dynamics in the polycrystalline ruthenium oxide Na3−xRu4O9 with one-dimensional structure. The line shape is composed of three peaks of Na+ ions on three different Na+ sites. Na+ ion motion is observed above 250 K and motional averaging of the sites completes at 390 K. The temperature dependence of NMR shift is thought closely correlated with the behavior of the magnetic susceptibility χ of 4d electrons of Ru4+.