Sánchez M C, Subías G, Pérez-Cacho J, García J, Blasco J
Instituto de Ciencia de Materiales de Aragón, C.S.I.C.-Universidad de Zaragoza, Spain.
J Synchrotron Radiat. 2001 Mar 1;8(Pt 2):901-3. doi: 10.1107/s0909049501000152.
X-ray absorption spectroscopy has been used to study LaNi1-x Mn(x)O3+delta perovskites (x = 0.1, 0.25, 0.5, 0.75, 0.9). We have analysed both, the oxidation state and the local structure around the transition metal atoms. XANES spectra of these samples suggest a mixed valence state for both transition metal atoms. The Mn K-edge is shifted to high energies as the Ni content is increased up to x=0.5. The opposite behavior is found instead, for the Ni K-edge. Samples with x=0.5 and x=0.25 present the Mn K-edge at the same energy but the absorption features are different for both samples. The local structure has also been studied by means of the EXAFS technique. The first coordination shell nicely reflects the structural change observed in this series from rhombohedral perovskites (x>0.5) to orthorhombic perovskites x<0.5). The changes in the local structure for Ni and Mn atoms agree with the variation of the oxidation state observed in the XANES spectra.
X射线吸收光谱已被用于研究LaNi1-x Mn(x)O3+δ钙钛矿（x = 0.1、0.25、0.5、0.75、0.9）。我们分析了过渡金属原子周围的氧化态和局部结构。这些样品的XANES光谱表明两种过渡金属原子均处于混合价态。随着镍含量增加至x = 0.5，锰的K边向高能方向移动。相反，对于镍的K边则观察到相反的行为。x = 0.5和x = 0.25的样品在相同能量处出现锰的K边，但两个样品的吸收特征不同。还通过EXAFS技术研究了局部结构。第一配位层很好地反映了该系列中从菱面体钙钛矿（x>0.5）到正交钙钛矿（x<0.5）所观察到的结构变化。镍和锰原子局部结构的变化与XANES光谱中观察到的氧化态变化一致。
