Fast Mapping of the Cobalt-Valence State in Ba0.5Sr0.5Co0.8Fe0.2O3-d by Electron Energy Loss Spectroscopy
Fast Mapping of the Cobalt-Valence State in Ba0.5Sr0.5Co0.8Fe0.2O3-d by Electron Energy Loss Spectroscopy
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DOI：
10.1017/s1431927613013536
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发表时间：
2013-10
影响因子：
2.8
通讯作者：
P. Müller;M. Meffert;H. Störmer;D. Gerthsen
中科院分区：
文献类型：
--
作者：
P. Müller;M. Meffert;H. Störmer;D. Gerthsen
本文介绍了一种在透射电子显微镜上用电子能量损失谱快速测定Co价态的方法。我们建议Co-L3和Co-L2的白线之间的距离作为确定2+和3+之间的Co价态的可靠性质。Co-L2，3白线距离的确定可以自动进行，因此非常适合于评估为行扫描和映射收集的大型数据集。由于采集时间短而具有低信噪比的数据可以通过应用主成分分析来处理。利用这种新技术研究了Ba_（0.5）Sr_（0.5）Co_（0.8）Fe_（0.2）O_（3-d）（BSCF）的Co价态。在650°C下退火100小时后，立方BSCF相的Co价态确定为2.2+（±0.2），而六方相的Co价态增加为2.8+（±0.2）。这些结果支持将立方BSCF相的不稳定性与在低于840°C的温度下增加的Co价态相关联的模型。
Abstract A fast method for determination of the Co-valence state by electron energy loss spectroscopy in a transmission electron microscope is presented. We suggest the distance between the Co-L3 and Co-L2 white-lines as a reliable property for the determination of Co-valence states between 2+ and 3+. The determination of the Co-L2,3 white-line distance can be automated and is therefore well suited for the evaluation of large data sets that are collected for line scans and mappings. Data with a low signal-to-noise due to short acquisition times can be processed by applying principal component analysis. The new technique was applied to study the Co-valence state of Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF), which is hampered by the superposition of the Ba-M4,5 white-lines on the Co-L2,3 white-lines. The Co-valence state of the cubic BSCF phase was determined to be 2.2+ (±0.2) after annealing for 100 h at 650°C, compared to an increased valence state of 2.8+ (±0.2) for the hexagonal phase. These results support models that correlate the instability of the cubic BSCF phase with an increased Co-valence state at temperatures below 840°C.