Atomic-Level Characterization of Dynamics of Copper Ions in CuAgSe

To examine the ionic migrations on atomic level in metal chalcogenide phonon glasses, Cu-63 solid state nuclear magnetic resonance (NMR) spectroscopy was performed in an archetype CuAgSe compound. The observed characteristic motional narrowing effect in the superionic state provide clear evidence for the model of single ion-hopping instead of free ion-like motion. We further find, for the first time, that thermal conductivity is strongly correlated with cation dynamics revealed by NMR within the range of temperatures investigated. This investigation provides better understanding how microscopic structure affects thermal transport properties which is of current interest in transition-metal chalcogenide based fast ion conductors.