Dynamics of silver ions in (AgI)x-(Ag2O-nB2O3)1−xglasses: AAg109nuclear magnetic resonance study

Abstract

Glasses having the composition (AgI${)}_{\mathit{x}}$-(${\mathrm{Ag}}_2$O-n${\mathrm{B}}_2$ ${\mathrm{O}}_3$ ${)}_{1\mathrm{-}\mathit{x}}$, where x is in the range from 0 to 0.7 and n is either 1 or 2, have conductivities as high as ${10}^{\mathrm{-}2}$ S/cm at room temperature. NMR line-shape and spin-lattice-relaxation times have been measured for a range of compositions over the temperature region from -120 to 170 °C in an attempt to test the predictions of various models for the dynamics of the ${\mathrm{Ag}}^{+}$ ions. The line shapes are Lorentzian except at very low temperatures, where they were determined to be Gaussian. The linewidths were observed to decrease with increasing temperature, and no evidence for two ${\mathrm{Ag}}^{+}$ populations was found. The spin-lattice-relaxation data feature a very broad ${\mathit{T}}_1$ minimum as a function of inverse temperature. Order-of-magnitude calculations suggest that the chemical shift interaction is responsible for the relaxation. Analysis using a single hopping rate for ${\mathrm{Ag}}^{+}$-ion migration does not fit the data. We have analyzed the data in terms of the empirical stretched exponential model and have found the resulting parameters to be in good agreement with the conductivity data.