Influence\nof Nonstoichiometry on Proton Conductivity in Thin-Film Yttrium-Doped\nBarium Zirconate

Abstract

Proton-conducting\nperovskites have been widely studied because of their potential application\nas solid electrolytes in intermediate temperature solid oxide fuel\ncells. Structural and chemical heterogeneities can develop during\nsynthesis, device fabrication, or service, which can profoundly affect\nproton transport. Here, we use time-resolved Kelvin probe force microscopy,\nscanning transmission electron microscopy, atom probe tomography,\nand density functional theory calculations to intentionally introduce\nBa-deficient planar and spherical defects and link the resultant atomic\nstructure with proton transport behavior in both stoichiometric and\nnonstoichiometric epitaxial, yttrium-doped barium zirconate thin films.\nThe defects were intentionally induced through high-temperature annealing\ntreatment, while maintaining the epitaxial single crystalline structure\nof the films, with an overall relaxation in the atomic structure.\nThe annealed samples showed smaller magnitudes of local lattice distortions\nbecause of the formation of proton polarons, thereby leading to decreased\nproton-trapping effect. This resulted in a decrease in the activation\nenergy for proton transport, leading to faster proton transport.