酸性水热合成CeO_2纳米颗粒的光学和磁学性质（英文）

Optical and magnetic properties of CeO_2 nanoparticles synthesized by a hydrothermal method in acid environment

以CeCl_3·7H_2O为铈源、NH3·H2O为矿化剂、HCl为酸性调节剂,利用水热法成功制备了二氧化铈纳米颗粒.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、紫外-可见分光光度计(UV-Vis)、荧光分光光度计(PL)、拉曼光谱(Raman)和振动样品磁强计(VSM)等分析测试手段,对CeO_2纳米颗粒的晶相、形貌、光学和磁学性质进行了表征.XRD测试结果表明样品的晶格参数略高于块状CeO_2的,并随着pH值的增大而减小.所有样品的形貌均为球形.从紫外-可见吸收光谱中,估计出的样品直接带隙值小于块状CeO_2的,且此值随pH值的增加而增加.pH值为2时合成样品具有室温铁磁性,此性质的出现可能与Ce^(3+)和氧空位的存在有关.

CeO2 nanoparticles were successfully synthesized by a hydrothermal method using CeCl3 · 7 H2O as cerium source, NH3 · H2O as mineralizer and HC1 as acidic regulator. The crystal phase, morphology, optical and magnetic properties of the as-synthesized CeO2 nanoparticles were characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM）, UV-Vis spectrophotometer （ UV-Vis ）, photoluminescence spectrometer （ PL ）, Raman spectrometer （Raman） and vibrating sample magnetometer （VSM）. It was found that the as-synthesized CeO2 nanoparticles had a fluorite structure, and there were defects and vacancies. The lattice parameter calculated from XRD spectra was slightly higher than bulk CeO2, and the lattice parameter decreased with the increase of pH value. The morphology of all samples was spherical. The direct band gaps estimated from the UV-Vis absorption spectra were smaller than that of bulk CeO2, and the band gaps increased with the increase of pH value. The sample synthesized at pH= 2 exhibited room temperature ferromagnetism （RTFM）, which was likely associated with the existence of Ce3＋ and oxygen vacancy.