本研究主要在探究稀磁性氧化物的磁性來源，透過化學沉澱法製成鈷摻雜二氧化鈰奈米粒子，並藉由改變氣氛退火條件、前驅物比例，以達到控制氧空缺濃度和鈷摻雜濃度，再探討這兩個條件與磁性之間的關係。
　　透過X光繞射(XRD)提供二氧化鈰的長程有序結構，確定其晶相為螢石結構，且無氧化鈷雜相存在，並搭配高解析度電子繞射顯微鏡(HRTEM)觀察到的實際影像，確定二氧化鈰大小均勻約在10奈米左右，使用X光精密吸收結構(XANES)分析，排除可能形成氧化鈷或金屬團聚的可能，並由延伸X光精密吸收結構(EXAFS)提供鈷原子周圍短程有序結構，確定鈷摻雜進入二氧化鈰主體中且處在鑲嵌的位置上。並由感應耦合電漿質譜分析儀(ICP-MS)確定各樣品鈷摻雜的實際濃度，且不含有鐵、鎳元素，排除樣品在製備過程被汙染的可能性。再透過拉曼光譜分析，拉曼頻率位移確定不同氣氛退火能有效的改變氧空缺濃度。磁性量測使用超導量子干涉儀(SQUID)，由室溫量測磁滯曲線得知所有樣品皆存在順磁性質，且在富含氧空缺樣品觀察到鐵磁性，確定氧空缺和鈷摻雜是存在鐵磁性質的必要條件，最後引入BMP(bounded magnetic polarons)理論，成功的利用BMP理論解釋鈷摻雜二氧化鈰奈米粒子系統，磁性變化與氧空缺和鈷摻雜濃度的關係。

In this research, the origin of magnetism in diluted magnetic oxides system has been investigated using a variety of different experimental methods. Cobalt doped cerium oxide nanoparticles were synthesized by chemical precipitation technique. It is possible to adjust the concentration of oxygen vacancies through oxygen or forming gas thermal annealing. The precursor ratio changes the concentration of cobalt dopant atoms. We have studied the correlation between magnetism and oxygen vacancies or concentration of doping cobalt in this DMO system. The long-range-order cerium oxide structure was investigated by X-ray diffraction (XRD). High resolution transmission electron microscopy (HRTEM) was used to obtain the images of cerium oxide nanoparticles. The result of cobalt K-edge x-ray absorption near-edge structure(XANES) ruled out the possibility of forming cobalt oxide or cobalt clusters. Extended x-ray absorption fine structure (EXAFS) measurements not only reveal the cobalt short-range-order structure but also confirm that cobalt atoms are on interstitial sites in the CeO2 host. Raman spectra provide the evidence that the concentration of oxygen vacancies increase after annealing in forming gas. The room temperature M-H curve reveals paramagnetism in all samples, and ferromagnetism in some oxygen vacancy rich samples, which implies an important correlation between oxygen vacancies, cobalt doping and ferromagnetism. Finally, the bounded magnetic polarons model was supported by our results to be responsible for the magnetism in cobalt doped cerium oxide nanoparticles.

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