Figure 2.

²³Na MAS NMR of 1-NNO featuring two distinct resonances (black curve): a fit of the quadrupolar environment with a center of mass at approximately −50 ppm (blue curve) and an overlaid experimental spectrum of NaNbO₃ (orange curve). Spectra were acquired at room temperature at 9.4 T and 12.5 kHz MAS. Box (a) shows the NaNb₁₃O₃₃ structure with its square-planar Na environment, which is assigned to the strongly quadrupolar line shape, while box (b) shows the Na environments in NaNbO₃. Grey spheres and polyhedra correspond to sodium, blue octahedra are NbO₆.