Localized Proton Motions in the Proton-Conducting Perovskites BaZr_1-x Sc _x O₃H _x (x=0.10 and 0.50) Investigated with Quasielastic Neutron Scattering

Acceptor-doped barium zirconates are fast proton conductors with a mechanism of proton conduction that involves proton transfers between neighboring oxide ions and rotational motions of the O-H species. Previous results from quasielastic neutron scattering (QENS) on Y-, Sc-, and In-doped BaZrO3, with a dopant concentration of up to 20%, show that the QENS signal may have contributions from several different proton transfer and O-H rotational motions, which are related to different local proton environments and which occur on similar timescales and with similar activation energies, largely independent of the type and concentration of dopant atom. Here, in a combined QENS and ab initio molecular dynamics (AIMD) simulation study, we show that the QENS signal of the more heavily doped material BaZr1-xScxO3Hx with x = 0.50 can be as well related to several different proton transfer and O-H rotational motions, spanning over a large range of timescales, yet with no significant differences in activation energies nor in the spatial geometry of the dynamics as compared to the systems with x <= 0.20. Further, we show that accessing momentum transfers of at least 4 & Aring;(-1) in the QENS data is a necessity in order to extract physically meaningful jump distances for the proton transfer and the O-H rotational process, respectively.