Cation dynamics of stabilized α-AgI in AgI-Ag₂O-MoO₃ glasses, studied by Ag-109 NMR spectroscopy

Ag-109 NMR spectra and their relaxation times were measured for composites containing stabilized α-AgI in glass matrices, which were prepared by a rapid quenching of melts (type A), or heating and consecutive cooling of the homogeneous glass (type B). Below -20 °C, the spectrum for the 74AgI·8.7Ag₂·O17.3MoO₃ composite of type B split into two peaks attributable to the α-AgI and the glass matrix. From this splitting, the exchange time τ_ex of silver ion between the α-AgI and the matrix glass was estimated to be about 0.3 ms at -20 °C. On the other hand, three peaks due to matrix glass, α-AgI and β-AgI were observed in the type A composite of 82AgI·6Ag₂O·12MoO₃, where no exchange was observed. Temperature dependence of the longitudinal relaxation time T₁ of stabilized α-AgI was measured for the first time. The value of τ_ex for the type B composite is in good agreement with that calculated from a jump diffusion model. The silver ions in the type B composites transfer more smoothly across the interface between the α-AgI and the glass matrix than those in type A composite.