纳米α-Fe~2O~3的XANES研究

选择纳米α-Fe~2O~3体系，运用X射线近边吸收谱(XANES)技术对纳米材料进行分析。结果表明，三种尺寸的纳米α-Fe~2O~3样品(颗粒尺寸分别是3nm，10nm和55nm)与粗颗粒商品的氧K边XANES谱的不同之处在于，纳米样品出现了一个新的吸收B峰。研究揭示，该峰可能是纳米α-Fe~2O~3中晶界部分氧的2p-4sp杂化所产生的一个新电子跃迁末态造成的。进一步的研究表明，随着纳米α-Fe~2O~3的粒子尺寸减小，氧的2p轨道和铁的3d轨道杂化增加，主要体现在2p-e~g杂化程度加剧，使得纳米颗粒中铁周围的氧配位八面体畸变程度加强。最后，通过对3nm样品在研磨和不研磨两种制样方式获得的氧K边XANES谱分析，证实纳米粒子体系中存在特殊的协同作用力。

Characterization of

α-Fe~2O~3 nanoparticles were chosen to study nanostructured materials by using X-ray absorption near edge structure (XANES) technique. It shows that oxygen K-edgy XANES spectra of all α- Fe~2O~3 nanoparticles of different sizes (3 nm, 10 nm and 55 nm) are different from that of commercial α-Fe~2O~3 coarse particles. the key feature with α-Fe~2O~3 nanoparticles is the occurrence of a new absorption peak labeled B in this paper. It reveals that peak B is attributed to the new states formed by the 2p states of grain boundary oxygen hybridized with iron 4s and 4p states. Further studies suggest that hybridization of oxygen 2p states with 3d metal states, mainly e~g orbital, increases as α-Fe~2O~3 nanoparticles decrease in their size, resulting in a bigger distortion of oxygen octahedrally local symmetry around the iron. Finally, we obtained both oxygen K-edge XANES spectra by making α-Fe~2O~3 nanoparticles (3 nm) directly for the experiment and making the same size nanoparticles after grinding. It proves that there is a special coordination force existing in nanostructured α-Fe~2O~3.