The Influence of Local Distortions on Proton Mobility in Acceptor Doped Perovskites

Abstract

Optimizing proton conduction in solids remains the most promising solution for achieving intermediate temperature (∼750–1000 K) solid oxide fuel cell devices, and enabling selective membranes for H2 separation. Proton conduction, a thermally activated process, exhibits its highest rates in yttrium (Y) acceptor doped BaZrO3 at an optimal doping level of 20% Y. The presence of extended defects such as grain boundaries has typically generated a wide variability in reported conductivity values. This has hindered a fundamental mechanistic understanding of how (acceptor) doping levels correlate with the activation energy of protons to produce an optimal doping level for fast proton transport. While isolated dopants have been suggested as the primary source of proton trapping, our results indicate that it is the local dopant-density that matters. Here, we show that increasing the local dopant density promotes localized lattice distortions in the presence of point defects such as oxygen-vacancies or proton inters...