Diffusion in amorphous LiNbO₃ studied by ⁷Li NMR - Comparison with the nano- and microcrystalline material

Lithium diffusion in amorphous LiNbO₃, synthesized by a sol-gel process, was investigated by temperature- and frequency-dependent ⁷Li NMR experiments. ⁷Li spin-lattice relaxation rates T₁^-1 and ⁷Li nuclear magnetic resonance spectra, in particular line shapes and motional narrowing of the central line, were measured. The results are discussed in comparison with those on nano- and microcrystalline LiNbO₃ investigated by us earlier. The Li diffusivity in the amorphous material is much higher than in the microcrystalline one and can be described by practically the same diffusion parameters as in nanocrystalline LiNbO₃. This suggests that the diffusion pathways in amorphous LiNbO₃ and in the interfacial regions of nanocrystalline LiNbO₃ have similar structures.