It was recalled that a first-order phase transition from a low-conductivity phase to a high-conductivity phase took place at 414K, and that the crystallographic structures of both phases had been established by means of high-resolution neutron powder diffraction. Quasi-elastic neutron scattering had provided information on the spatial and temporal characteristics of proton transport. Monte Carlo modelling of neutron diffraction total scattering data made it possible here to deduce the diffusion pathways of protons. The results were in good agreement with a previously proposed qualitative model for proton transport. In particular, it was clearly shown that proton motion was highly correlated with the rotation of sulphate groups. In the case of the low-temperature phase, a weak correlation between protons and O atoms on the next-nearest neighbour sulphate group was identified. This increased with temperature and was suggested to drive the phase transition.

Structure and Proton Conduction in CsDSO4. P.Zetterstrom, A.V.Belushkin, R.L.McGreevy, L.A.Shuvalov: Solid State Ionics, 1999, 116[3-4], 321-9