While 27Al MAS NMR spectroscopy reveals the presence of only octahedral [AlO6] environments for Li1.6Al0.6Ge1.4(PO4)3, Li1.2Al0.6Ti1.4(PO4)3 exhibits large amounts of Al located in tetrahedral [AlO4] environments. 31P MAS NMR measurements reveal multiple environments with different Al/Ge next nearest neighbor composition around P and the relative intensities are in good agreement with a statistical arrangement of Ge/Al on the octahedral sites for Li1.6Al0.6Ge1.4(PO4)3. For Li1.2Al0.6Ti1.4(PO4)3, the 31P MAS NMR results indicate the presence of structural disorder. These results are confirmed by X-ray diffraction and Rietveld refinements.
The dynamics of Li ions have been investigated by temperature-dependent static 7Li NMR lineshape analysis and 7Li NMR relaxometry. Jump rates of about 7∙108 s-1 can be estimated for Li1.6Al0.6Ge1.4(PO4)3 at 400 K and the activation barrier for a single Li ion jump is 0.14 eV. A Li diffusion coefficient of 10-11 m2/s and a Li ion conductivity of 3.6 mS/cm can be estimated at 400 K.
For Na3.4Sc2(SiO4)0.4(PO4)2.6, NMR spectroscopy reveals that Si and P are arranged statistically on the tetrahedral sites and Sc is exclusively located on octahedral sites. Temperature-dependent 23Na NMR measurements show a strong increase of the asymmetry of the local environment, consistent with XRD measurements which yield a strongly anisotropic thermal expansion. Jump rates of higher than 5∙103 s-1 can be estimated for the Na ions for temperatures above 300 K.