AMMONIUM ION MOTIONS IN THE HEXAGONAL TUNGSTEN TRIOXIDE FRAMEWORK - A H-1-NMR STUDY OF (NH4)XWO3

The temperature and frequency dependences of the 1H NMR relaxation time T2 and T1 have been studied for ammonium tungsten bronze (NH4)xWO3(x=0.23). Data analysis leads to characterisation of three distinct motions: dissociative diffusion of protons, very low activation barrier reorientation of NH+4 and short-range hopping of NH+4 along the hexagonal tunnels of the structure. The spectral density function of the hopping, determined by temperature-frequency superposition, is consistent with low-dimensional motion and gave an activation energy of around 22 kJ mol-1. © 1990.