Nuclear magnetic resonance study of superprotonic conductor Rb4LiH3(SO4)4 single crystals.

To investigate the molecular dynamics of a Rb4LiH3(SO4)4 crystal below superionic phase transitions, we examined the temperature dependences of the NMR spectra and the spin-lattice relaxation time, T1, of the (1)H, (7)Li, and (87)Rb nuclei. The symmetry of (1)H signals resembles the Pake doublet containing a pair of dipolar-coupled protons. From the temperature dependence of T1, the activation energy of proton at high temperature is twice of those of (7)Li and (87)Rb. A striking feature was the formation of the weak hydrogen bond creating a significant influence of proton at high temperatures due to the mobility of the hydrogen-bond protons. And, we compared these data with (1)H and (7)Li results for (NH4)4LiH3(SO4)4 and K4LiH3(SO4)4 crystals, which have similar structures.
(© 2013 Elsevier Inc. All rights reserved.)