NMR study of fluorine and proton motion in the ionic conductor NH4Sn2F5

Abstract The nuclear spin relaxation times of protons and fluorine atoms in the ionic conductor NH 4 Sn 2 F 5 show a particular temperature behaviour: they decrease as the temperature decreases below 200 K and have the same temperature and frequency dependences. Cross relaxation experiments show an important coupling between fluorine atoms and protons. NMR results as well as crystallographic and conductivity data on hydrogenated and deuterated compounds, allow to determine two dominant kinds of motion: at low temperature the reorientation of the ammonium ion is observed and above 250 K the diffusion of the fluorine atoms is responsible for the relaxation. In the high temperature range, the activation energies of the motion deduced from conductivity and NMR measurements are in good agreement.