Translational diffusion of NH4+ ions in [(NH4)1−xRbx]3H(SO4)2 was evaluated quantitatively by means of 1H spin-lattice relaxation times in the rotating frame, T1ρ. In the high-temperature phase (phase I), the mean residence times of NH4+ ions were three or four orders of magnitude larger than those of the acidic protons. In the room-temperature phase (phase II), they were two or three orders of magnitude larger than those of the acidic protons. The transition from phases II to I causes one order of magnitude enhancement in the diffusion of NH4+ ions. The mean residence time of NH4+ ions increases with increase in the Rb content. The similar trend was also observed in phase II.

Diffusion of Ammonium Ions in [(NH4)1-xRbx]3H(SO4)2 Studied by 1H Spin-Lattice Relaxation in the Rotating Frame. S.Hayashi, H.Omi: Journal of Physics and Chemistry of Solids, 2012, 73[4], 614-6