Films of La0.8Sr0.2CoO3-δ (LSC-82) with 45 and 90 nm thickness were grown epitaxially on (001) oriented single crystal yttriastabilized zirconia with a thin gadolinium-doped ceria interlayer using pulsed laser deposition, and characterized using X-ray diffraction (XRD), depth-profile secondary mass spectrometry (DP-SIMS), and linear and nonlinear electrochemical impedance spectroscopy (EIS and NLEIS). The films were found to exhibit in-plane tensile strain and normal compressive strain (with overall increased lattice volume) relative to freestanding cubic LSC-82. The films also possess a compositional La/Sr gradient across their thickness, with enhanced Sr2+ composition (within the perovskite lattice) at the gas-exposed surface. The oxygen storage capacity of the films at 450-600°C (as measured using EIS capacitance) is greatly enhanced relative to freestanding cubic LSC-82, consistent with an apparent increase in oxygen-vacancy concentration at the gas-exposed surface of the films (as revealed by NLEIS). These results can be explained by a two-layer model in which a finite thickness of the perovskite lattice near the surface has an enhanced Sr dopant concentration, leading to a much higher concentration of oxygen vacancies than the underlying bulk material of nominal Sr composition. The nonlinear electrochemical response of the film is consistent with a dissociative adsorption rate law, provided the enhanced bulk vacancy concentration near the surface is included in the analysis. © 2013 The Electrochemical Society. All rights reserved.
KAUST Repository Item: Exported on 2021-09-21
Acknowledgements: This work was supported in part by National Science Foundation Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET) under award numbers 0829171 and 0844526, the U.S. Department of Energy (SISGR DE-SC0002633) and King Abdullah University of Science and Technology. Work at ORNL (including contributions by MDB and HMC) was supported by the U.S. Department of Energy, Basic Energy Sciences, Scientific User Facilities Division.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.