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

Abstract

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, T-1, of the H-1, Li-7, and Rb-87 nuclei. The symmetry of H-1 signals resembles the Pake doublet containing a pair of dipolar-coupled protons. From the temperature dependence of T-1, the activation energy of proton at high temperature is twice of those of Li-7 and Rb-87. 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 H-1 and Li-7 results for (NH4)(4)LiH3(SO4)(4) and K4LiH3(SO4)(4) crystals, which have similar structures. (C) 2013 Elsevier Inc. All rights reserved.