Y:BaZrO3 Perovskite Compounds II: Designing Protonic Conduction by using MD Models

The proton dynamics in Y-doped BaZrO3 derivatives, in particular the different dopant environments within a Pm${\bar 3}$m cubic framework, were studied by using classical molecular dynamics (MD) calculations. Single- and double substitution of zirconium by yttrium atoms was considered. The presence of yttrium induced variations in the surrounding oxygen sites, according to their local geometrical arrangements. The differences among such distinct oxygen sites became evident when protons interacted with them and upon changes in the temperature. So, different proton transfer pathways, which had different energy barriers, characterized the topologically different oxygen sites. The experimental proton-hopping activation energy was only reproduced in those structures in which two yttrium atoms formed a Y-O-Y arrangement, which also acted as multilevel protonic traps. Protonic conduction in these materials could be improved by avoiding such yttrium clustering, hence preventing the formation of the protonic traps.