Dynamics of superionic Rb 3H(SeO 4) 2 single crystals studied by 1H and 87Rb spin–lattice relaxation

Abstract

The 1H and 87Rb spin–lattice relaxation and spin–spin relaxation times in superionic Rb 3H(SeO 4) 2 single crystals grown by the slow evaporation method were measured over the temperature range 160–450 K. The temperature dependencies of the 1H T 1, T 1 ρ , and T 2 are measured. In the ferroelastic phase, T 1 differs from T 1 ρ , which is in turn different from T 2, although these three relaxation times converge to similar values near 410 K. This transition seems to occur at temperature which is about 40 K lower than the superionic transition temperature. The observation of liquid-like values of the 1H T 1, T 1 ρ , and T 2 in the high temperature is compatible with the phase being superionic, indicating that the destruction and reconstruction of hydrogen bonds does indeed occur at high temperature. In addition, the 87Rb T 1 and T 2 values at high temperature were similar (on the order of milliseconds), a trend that was also observed for 1H T 1 and T 2. This behavior is expected for most hopping-type ionic conductors, and could be attributed to interactions between the mobile ions and the neighboring group ions within the crystal. The motion giving rise to this liquid-like behavior is related to the superionic motion.