Cobaltite oxides, like Ba(La)CoO_3, are very promising candidates as cathode materials for solid oxide fuel cells and electrolysers (SOFCs and SOECs). Lattice distortions have been shown as a promising approach to improve cathodic properties. To investigate this possible approach, biaxial strain is induced on model systems, i.e. through the epitaxial growth of barium lanthanum cobaltite on single crystalline substrates. The influence of strain on the oxidation state of cobalt is probed through energy electron loss spectroscopy. XRD measurements indicate that films with biaxial compressive strain exhibit a larger unit cell volume. Electron energy-loss spectroscopy (EELS) shows that biaxial compressive strain induces a higher Co²⁺/Co³⁺ ratio, probably enabled through the larger ionic radius of Co²⁺. Electrical conductivity relaxation measurements reveal that the activation energy for the surface exchange is decreased with the increasing amount of Co²⁺. This strongly indicates the connection between the unit cell volume, the oxidation state of cobalt, and the surface exchange kinetics of Ba(La)CoO₃. An improved understanding of the fundamental kinetics in cathode materials for SOFCs is important for further materials development.

中文翻译：

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应变对Y2O3稳定ZrO2上钡镧钴钴薄膜中Co氧化态和氧离解活性的影响

钴氧化物，如Ba（La）CoO _3，是非常有希望的候选材料，可作为固体氧化物燃料电池和电解槽（SOFC和SOEC）的阴极材料。晶格畸变已被证明是改善阴极性能的一种有前途的方法。为了研究这种可能的方法，在模型系统上感应双轴应变，即通过在单晶衬底上外延生长钡镧钴酸钴。应变对钴氧化态的影响通过能量电子损耗光谱法进行了探讨。XRD测量表明具有双轴压缩应变的膜表现出较大的晶胞体积。电子能量损失谱（EELS）表明，双轴压缩应变引起较高的Co ²⁺ / Co ³⁺比率，可能是通过更大的Co ²⁺离子半径实现的。电导率弛豫测量表明，随着Co ²⁺的增加，用于表面交换的活化能降低。这有力地表明了晶胞体积，钴的氧化态和Ba（La）CoO ₃的表面交换动力学之间的联系。进一步了解SOFC阴极材料基本动力学的理解对于进一步开发材料很重要。