Acceptor doped perovskites (ABO3) are a promising class of materials that find application in intermediate temperature solid oxide fuel cells. For example, yttrium doped barium zirconate (Y-BZO) has been widely investigated, due in part to its high proton conductivity and excellent chemical stability at intermediate temperatures. In order to understand the complex interplay between dopant induced lattice distortion and proton transport we first synthesized a series of model epitaxial Y-BZO thin films on [100] oriented single crystal MgO substrate using pulsed laser deposition, with Y-dopant concentrations ranging from 5 to 20%. Time resolved Kelvin probe force microscopy was then used for surface potential mapping as a function of dopant concentration, humidity, and temperature in order to extract the activation energies for proton transport. The activation energy increases (0.45 – 0.64 eV) with increasing dopant concentration (5 to 20% Y). We infer a strong correlation between activation energy and dopant lattice distortions by quantifying and mapping B-site bond-angle deviation and atomic displacement from atomically resolved scanning transmission electron microscopy images for each of the Y-BZO thin films. The combination of these results suggests that proton trapping occurs near Y-dopant atoms and therefore, material design strategies can be developed to determine the optimal B-site acceptor dopants such that lattice distortion, interaction energy, and proton trapping can be minimized. The research was sponsored by the Laboratory Directed Research and Development Program fund at the Oak Ridge National Laboratory. Computations were performed at National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy.

Multi-modal approach to understand proton transport mechanisms in Y-doped barium zirconate

254th National Meeting (2017)

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