References

Solid-state diffusion plays one of the most important roles in materials science. In particular, the precise measurement of ion dynamics in materials with structural disorder is of great interest. Spin-alignment echo (SAE) nuclear magnetic resonance (NMR), being comparable to exchange spectroscopy, turned out to be a powerful method to probe (ultra-)slow Li dynamics even in amorphous materials [1, 2]. However, 7Li Jeener-Broekaert echoes can be influenced by the simultaneous generation of dipolar with quadrupolar order. In many cases, the first can be suppressed by choosing proper evolution times tp of less than 20 µs [3]. Here, glassy Li2Si3O7 served as a suitable model system to study the positive influence of isotope dilution on 7Li SAE NMR, i.e., the reduction of homonuclear dipole-dipole interactions through spatial separation of the spin-3/2 probe nuclei. Two samples, one with 100 % 7Li and the other one with 5 % 7Li (95 % 7Li), were investigated by 7Li NMR line-shape analysis, spin-lattice relaxation NMR as well as mixing-time and preparation-time dependent 7Li SAE NMR using a 32-fold phase cycle. Jeener-Broekaert echoes and their Fourier transforms show that at sufficiently short tp the interfering dipolar interactions can be completely suppressed in that sample for which the proportion of 7Li was greatly reduced by substitution with 6Li. The so-obtained diffusion parameters are compared with results deduced from broadband conductivity spectroscopy