本研究利用熱沉澱法製備 掺雜 Fe 及 Cr 的 CeO2 奈米粉末。製備完成的奈米粉末利用吸收光譜 (X-ray AbsorptionSpectroscopy，XAS) 量測其電子及原子結構。奈米粉末的粒徑大小及室溫鐵磁性 (Room-Temperature Ferromagnetism, RTFM)則分別利用X 光繞射儀 (XRD) 及超導量子干涉磁化儀 (Superconducting Quantum Interference Device Magnetometer, SQUID) 進行分析。延伸 X 光吸收精細結構 (The Extended X-ray Absorption Fine Structure (EXAFS)) 則是用來分析奈米粉末中元素的配位數及鍵長的改變。結果顯示，摻雜進入奈米粉末的 Cr 及 Fe 均為三價；Cr 摻雜量增加時會造成 Ce3+ 比例的增加 ; CeO2 摻雜 Fe 時，隨著 Fe 摻雜的提升會造成 Ce3+ 比例減少。不同價數的變化會產生不同的取代方式，藉由磁性結果做比較，可發現 CeO2 摻雜不同元素 Fe 及 Cr 時，價數的變化會造成飽和磁化量呈現不同的趨勢。藉由此磁性結果做比較可以建立CeO2 摻雜不同元素的磁性機制。

The Fe-doped and Cr-doped CeO2 nanoparticles were prepared by the precipitation method. The systematic electronic structure and atomic structure of the NPs were investigated by X-ray Absorption Spectroscopy (XAS). The particle size and the magnetic properties of the NPs were characterized by XRD and Supercunducting Quantum Interference Device (SQUID) magnetometer. The Extended X-ray Absorption Fine Structure (EXAFS) spectra provide the information about the first shell coordination and bound length of Fe doped CeO2. The X-ray Absorption Near Edge Structure (XANES) indicated the doped Fe and Cr elements are tri-valence inside the CeO2 NPs, and the valence state of Ce varied with Fe/Cr doping. In Fe:CeO2, the concentration of Ce3+ decreased as the doping concentration increased. On the contrary, the concentration of Ce3+ increased with increasing the concentration of Cr. Combining the results of XAS and SQUID, different results of substitution by Fe and Cr ions in the CeO2 matrix were then proposed. The effect of dopant on the magnetism was then explained by the BMP model and the formation of paired ion.

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