Na-23 NMR study of NASICON-type compounds, Na1+xScxTi2-x(PO4)(3)

The structure of NASICON-type compounds, Na1+xSCxTi2-x(PO4)(3) (0 less than or equal to x less than or equal to 2), and the dynamics of Na+ have been investigated by Na-23 NMR spectroscopy. It was found that the 23Na 1D and 2 D MQMAS spectra depend on the Na concentration, suggesting strongly that th e Na+ ions are distributed between two crystallographically nonequivalent s ites, one is a special position with axial symmetry, and the other a positi on of low symmetry. The chemical exchange between these different sites in the crystal takes place at room temperature, which may cause the high Na io n conduction of this material.