Structure and cation dynamics in the system AgI:Ag2MoO4:: A 109Ag NMR study

The system (AgI)(1-x)(Ag2MoO4)(x) is studied with Ag-109 solid-state NMR and differential scanning calorimetry. Glasses are formed for 0.2<x<0.4. Outside the glass formation region a glassy phase of molar composition 0.66 AgI-0.33 Ag2MoO4 is always found, which is accompanied by beta-AgI or Ag2MoO4 crystals. Upon thermal treatments above 120 degrees C, a 0.66 AgI-0.33 Ag2MoO4 (2:1) phase crystallizes over the entire composition range. The chemical shift anisotropy Censor of this phase has been assigned. The anisotropy is similar to 70 ppm, that is an order of magnitude lower than the isotropic chemical shift range observed in silver borate glasses. The addition of AgI to Ag2MoO4 causes the formation of oxy-iodide sites. The existence of AgI clusters can be ruled out. Spin-lattice relaxation inside the glass-formation region seems to be controlled by Ag-I scalar coupling of the first kind, rather than by chemical shift anisotropy. The existence of two maxima in the spin-lattice relaxation rate curve points towards Ag+ populations with different mobility. [S0163-1829(98)05537-4].