It was demonstrated that 1-dimensional and 2-dimensional 109Ag NMR was well suited to study diffusion in crystalline and glassy Ag ion conductors. In 1D 109Ag NMR, especially when applying magic angle spinning, the local environments of the Ag sites could be characterized. 2D 109Ag NMR allows one to record two-time correlation functions which directly monitor dynamics of single Ag ions. These techniques were used to elucidate microscopic properties of polycrystalline Ag7P3S11. In this Ag ion conductor, Ag+ motion results in non-exponential correlation functions which decay to a finite plateau value. At all temperatures, the data were well described by a modified Kohlrausch function f(t) = (1-C)exp[-(t/τ)β]+C, where β was about 0.42 and C was about 0.12. The temperature dependence of the mean correlation time <τ> obeyed an Arrhenius law with an activation energy Ea = 0.37eV. The results indicated that 109Ag NMR probed elementary Ag ion jumps which were the basis of macroscopic ion transport. In addition, an investigation was made, for the first time, of dynamics in glassy ion conductors by means of 2D NMR. In the glasses (AgI)0.3–(AgPO3)0.7 and (AgI)0.3–(1/3)(Ag4P2O7)0.7 glasses, Ag motion manifests itself in correlation functions which decayed in an extremely stretched manner, i.e., β = 0.21, to C = 0. Hence, there was no evidence for domain segregation into silver phosphate glass and AgI clusters, in which case a bimodal rate distribution would be expected.

Silver Dynamics in Crystalline and Glassy Silver Ion Conductors Studied by One- and Two-Dimensional 109Ag NMR. M.Vogel, C.Brinkmann, H.Eckert, A.Heuer: Journal of Non-Crystalline Solids, 2002, 307-310, 971-80