Silver dynamics in crystalline and glassy silver ion conductors studied by one- and two-dimensional 109 Ag NMR M. Vogel * , C. Brinkmann, H. Eckert, A. Heuer Institut f€ ur Physikalische Chemie, Westf€ alische Wilhelms-Universit€ at, Schlossplatz 7, D 48149 M€ unster, Germany Abstract We demonstrate that one- (1D) and two-dimensional (2D) 109 AgNMRiswellsuitedtostudydiffusionincrystalline and glassy silver ion conductors. In 1D 109 Ag NMR, especially when applying magic angle spinning, the local envi- ronments of the silver sites can be characterized. 2D 109 Ag NMR allows one to record two-time correlation functions which directly monitor dynamics of single silver ions. These techniques are used to elucidate microscopic properties of polycrystalline Ag 7 P 3 S 11 . In this silver ion conductor, Ag þ motion results in non-exponential correlation functions which decay to a finite plateau value. At all temperatures, the data are well described by a modified Kohlrausch function f ðtÞ¼ð1  CÞ exp½ðt=sÞ b þ C, where b  0:42 and and C  0:12. The temperature dependence of the mean correlation time hsi obeys an Arrhenius law with activation energy E a ¼ 0:37 eV. Our results indicate that 109 AgNMR probeselementarysilverionjumpswhicharethebasisofmacroscopiciontransport.Inaddition,weinvestigateforthe first time dynamics in glassy ion conductors by means of 2D NMR. In the glasses (AgI) 0:3 –(AgPO 3 ) 0:7 and (AgI) 0:3 – (1/3)(Ag 4 P 2 O 7 ) 0:7 , silver motion manifests itself in correlation functions which decay in an extremely stretched manner, i.e., b ¼ 0:21,to C ¼ 0.Hence,thereisnoevidencefordomainsegregationintosilverphosphateglassandAgIclusters, in which case a bimodal rate distribution would be expected. Ó 2002 Elsevier Science B.V. All rights reserved. 1. Introduction In recent years, there has been rapidly growing interest in materials with high ionic conductivity because of their potential applications as solid- state electrolytes in new electrochemical devices suchassolid-statebatteries,fuelcellsandchemical sensors.Inviewofthiswidefield,alargevarietyof solid ion conductors has been developed. In all of these materials, elementary jumps of mobile ions occurring in an essentially frozen matrix form the basis of the macroscopic transport. Thus, it is a prerequisite for the future design of solid-state electrolytes to understand the mechanism of ion dynamics on a microscopic scale. In particular, one should address the question to which extent, on the one hand, heterogeneous dynamics and, on the other, a special motional mechanism including correlated forth-and-back jumps contribute to the non-exponential relaxation observed in several ex- periments. Moreover, it is worth knowing whether ionic motion is assisted by some small fluctuations of the matrix. Journal of Non-Crystalline Solids 307–310 (2002) 971–980 www.elsevier.com/locate/jnoncrysol * Corresponding author. Present address: Department of Chemical Engineering, University of Michigan 2300 Hayward, Ann Arbor, MI 48109, USA. E-mail address: mivogel@engin.umich.edu (M. Vogel). 0022-3093/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0022-3093(02)01562-4