Strain-induced structure and oxygen transport interactions in epitaxial La 0.6 Sr 0.4 CoO 3−δ thin films

The possibility to control oxygen transport in one of the most promising solid oxide fuel cell cathode materials, La0.6Sr0.4CoO3−δ, by controlling lattice strain raises questions regarding the contribution of atomic scale effects. Here, high-resolution transmission electron microscopy revealed the different atomic structures in La0.6Sr0.4CoO3−δ thin films grown under tensile and compressive strain conditions. The atomic structure of the tensile-strained film indicated significant local concentration of the oxygen vacancies, with the average value of the oxygen non-stoichiometry being much larger than for the compressive-strained film. In addition to the vacancy concentration differences that are measured by isotope exchange depth profiling, significant vacancy ordering was found in tensile-strained films. This understanding might be useful for tuning the atomic structure of La0.6Sr0.4CoO3−δ thin films to optimize cathode performance. Strain engineering can enhance oxygen transport in cathodes in solid oxide fuel cells. Here, atomic scale imaging is used to probe local structures in tensile- and compressive-strained La0.6Sr0.4CoO3-δ films, revealing higher oxygen vacancy concentration in tensile films, and vacancy ordering.