AG-109 NMR of AgI Based Superionic Conductor Glasses

Recent experiments on Ag-109 NMR of AgI based superionic conductor glasses are reviewed. The composition dependence of the average chemical shift is correlated with the ionic conductivity, which is explained by the local bond covalency between Ag⁺ and surrounding anions. An NMR spectrum was apparently composed of a narrow Lorentzian peak due to the fast mobile silver ions and broad Gaussian components from slow ions, the intensity ratio of which depends on the composition and the temperature. The width of the broad Gaussian component is mainly determined by heterogeneous chemical shift distribution owing to the variety of the chemical environment of the silver ions. The temperature dependence of the NMR spectra can be well simulated by multi-site exchange model, where the exchange of the silver cations among differently coordinated sites are taken into account, which was also demonstrated by a recent observation of NMR hole-burning experiment.