Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA.
ACS Appl Mater Interfaces. 2012 May;4(5):2541-50. doi: 10.1021/am300194n. Epub 2012 May 14.
Substrate- and thickness-related effects on the oxygen surface exchange of La(0.7)Sr(0.3)MnO(3) (LSM) thin films were investigated to understand better cathode reactivity in solid oxide fuel cells. Epitaxial (100)-oriented LSM films were fabricated on (100)-SrTiO(3) and (110)-NdGaO(3) substrates and were characterized using electrical conductivity relaxation. A strong substrate effect on the chemical surface exchange coefficient (k(chem)) was observed, with a higher k(chem) found for films on SrTiO(3) than those on NdGaO(3). Two distinct activation energies (E(a)) were observed for k(chem), which were assigned to two parallel exchange processes; the relative contributions from each depended on the substrate, film thickness, and temperature. For films coherently strained to the substrates, k(chem) values differed by almost an order of magnitude, whereas E(a) was ∼1.5 (± 0.1) eV on both substrates. For relaxed films, k(chem) values differed only by a factor of 2, and E(a) was ∼0.75 (± 0.1) eV on both substrates. We discuss the strain effect relative to the native surface exchange and the thickness effect relative to the extended defect populations in the films. The outcome of this study sheds light on how microstructural features affect surface chemistry in modified cathodes.
研究了 La(0.7)Sr(0.3)MnO(3)（LSM）薄膜的衬底和厚度相关效应对氧表面交换的影响，以更好地理解固体氧化物燃料电池中阴极的反应性。在（100）-SrTiO(3) 和（110）-NdGaO(3) 衬底上制备了外延（100）取向的 LSM 薄膜，并使用电导率弛豫进行了表征。观察到化学表面交换系数（k(chem)）对衬底有很强的影响，在 SrTiO(3) 上的薄膜的 k(chem) 高于在 NdGaO(3) 上的薄膜。观察到 k(chem) 的两个不同的激活能（E(a)），它们被分配到两个平行的交换过程；每个过程的相对贡献取决于衬底、薄膜厚度和温度。对于与衬底完全应变的薄膜，k(chem) 值的差异几乎相差一个数量级，而在两个衬底上，E(a) 约为 1.5（±0.1）eV。对于弛豫的薄膜，k(chem) 值的差异仅为 2 倍，在两个衬底上，E(a) 约为 0.75（±0.1）eV。我们讨论了应变效应对本征表面交换的影响，以及厚度效应对薄膜中扩展缺陷群体的影响。这项研究的结果阐明了微观结构特征如何影响改性阴极中的表面化学。
