Complex hopping dynamics in the deuteron conductors K3D(SO4)2 and Rb3D(SO4)2

Abstract

The translational deuteron motions in the paraelectric phases of K3D(SO4)2 and Rb3D(SO4)2 were studied using two-dimensional exchange nuclear magnetic resonance, performed in the frequency as well as in the time domains. These experiments reveal that in Rb3D(SO4)2 the ion hopping is about one order of magnitude slower than in K3D(SO4)2. Additional measurements of the spinlattice relaxation times were carried out at the proton, deuteron, and rubidium sites. It was found that the relaxation times determined for deuterated as well as for protonated tri-rubidium-hydrogen-disulfates are a factor of ten longer than those for the corresponding tri-potassium-hydrogen-disulfates. The results reveal that the deuteron hopping is to be regarded as a two-step process involving a coupling to rotational or librational motions of the sulfate tetrahedra.