Local structure of Fe in Fe-doped misfit-layered calcium cobaltite: An X-ray absorption spectroscopy study
Local structure of Fe in Fe-doped misfit-layered calcium cobaltite: An X-ray absorption spectroscopy study
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DOI：
10.1016/j.jssc.2013.05.038
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发表时间：
2013-08
影响因子：
3.3
通讯作者：
N. Prasoetsopha;S. Pinitsoontorn;Atipong Bootchanont;P. Kidkhunthod;P. Srepusharawoot;T. Kamwanna;V. Amornkitbamrung;K. Kurosaki;S. Yamanaka
中科院分区：
文献类型：
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作者：
N. Prasoetsopha;S. Pinitsoontorn;Atipong Bootchanont;P. Kidkhunthod;P. Srepusharawoot;T. Kamwanna;V. Amornkitbamrung;K. Kurosaki;S. Yamanaka
使用简单的热氢分解方法和放电等离子烧结技术制备了多晶 Ca3Co4−xFexO9+δ 陶瓷（x=0、0.01、0.03、0.05）。热电性能测量表明，增加 Fe 浓度会导致电阻率、热电势和热导率降低，从而改善无量纲品质因数，在 1073 K 时 >35% forx=0.05。X 射线吸收光谱技术首次用于研究 Ca3Co4−xFexO9+δ 结构中 Fe 离子的局域结构。通过拟合扩展X射线吸收精细结构（EXAFS）光谱数据并结合第一原理模拟分析X射线吸收近边结构（XANES）光谱，表明Fe在Ca2CoO3（岩盐，RS）层中取代了Co，而不是在CoO2层中。热电性能随 Fe 浓度变化的变化归因于 CoO2 和 RS 层之间的电荷转移。考虑到 Co 和 Fe 的离子半径以及系统的总能量，研究了优先 Fe 取代位点的起源。
Polycrystalline Ca3Co4−xFexO9+δceramics (x=0, 0.01, 0.03, 0.05) were fabricated using a simple thermal hydro-decomposition method and a spark plasma sintering technique. Thermoelectric property measurements showed that increasing Fe concentration resulted in a decrease in electrical resistivity, thermopower and thermal conductivity, leading to an improvement in the dimensionless figure-of-merit, >35% forx=0.05 at 1073 K. An X-ray absorption spectroscopy technique was used to investigate the local structure of Fe ions in the Ca3Co4−xFexO9+δstructure for the first time. By fitting data from the extended X-ray absorption fine structure (EXAFS) spectra and analyzing the X-ray absorption near-edge structure (XANES) spectra incorporated with first principle simulation, it was shown that Fe was substituted for Co in the the Ca2CoO3(rocksalt, RS) layer rather than in the CoO2layer. Variation in the thermoelectric properties as a function of Fe concentration was attributed to charge transfer between the CoO2and the RS layers. The origin of the preferential Fe substitution site was investigated considering the ionic radii of Co and Fe and the total energy of the system.