Quasielastic neutron scattering of hydrated BaZr_{0.90}A_{0.10}O_{2.95} (A = Y and Sc)

TL;DR

This study uses quasielastic neutron scattering to investigate localized proton motions in hydrated BaZr_{0.90}A_{0.10}O_{2.95} (A=Y, Sc), revealing low-energy intra-octahedral transfers near dopants that are not rate-limiting for conductivity.

Contribution

It provides new insights into the microscopic proton dynamics in doped perovskites and links experimental results with density functional theory calculations.

Findings

Protons exhibit localized intra-octahedral motions on ps timescales.

Activation energy for this motion is approximately 10-30 meV.

Proton motion onset occurs around 300 K.

Abstract

Proton motions in hydrated proton conducting perovskites BaZr_{0.90}A_{0.10}O_{2.95} (A = Y and Sc) have been investigated using quasielastic neutron scattering. The results reveal a localized motion on the ps time scale and with an activation energy of ~10-30 meV, in both materials. The temperature dependence of the total mean square displacement of the protons suggests an onset of this motion at a temperature of about 300 K. Comparison of the QENS results to density functional theory calculations suggests that for both materials this motion can be ascribed to intra-octahedral proton transfers occurring close to a dopant atom. The low activation energy, more than ten times lower than the activation energy for the macroscopic proton conductivity, suggests that this motion is not the rate-limiting process for the long-range proton diffusion, i.e. it is not linked to the two materials significantly different proton conductivities.