Proton dynamics in a spark-plasma sintered BaZr_0.7Ce_0.2Y_0.1O_3- proton conductor investigated by quasi-elastic neutron...

The thermally activated proton dynamics in the perovskite lattice of spark-plasma sintered BaZr_0.7Ce_0.2Y_0.1O_3-δ was investigated by quasi-elastic neutron scattering (QENS) and electrochemical impedance spectroscopy (EIS) in the temperature range from 200-600 °C. The quasi-elastic signal could be resolved into two components corresponding to a translational and rotational motion. From a description of the diffusive movements with the Chudley-Elliot jump diffusion model a jump distance of 3.12 Å and residence time of 13.6 ps were found for the translational protonic diffusion at 600 °C. The diffusion coefficients for QENS and EIS follow an Arrhenius law with activation energies of 0.16 eV, 0.58 eV and 0.88 eV for the microscopic proton self-diffusion, the bulk and grain boundaries, respectively. The rotational motion was analyzed using a two-site jump and a spherical rotation model which resulted in O-H distances of 0.89 Å and 0.71 Å, respectively. The data provided by the two-site jump model evidences the Grotthuss-type mechanism behind the translational proton dynamics.