水热法合成胶囊状CeO2及其室温铁磁性

Hydrothermal Synthesis of Capsule-like CeO2 and Their Room Temperature Ferromagnetism

为研究CeO2室温铁磁性起源,实验采用水热法,以Ce(NO3)3·6H2O为铈源,CO(NH2)2为沉淀剂,PVP为表面活性剂,HNO3调节溶液酸碱度,通过改变尿素用量制备CeO2产物.当尿素量为8 mmol时,产物为胶囊状CeO2,长200~300 nm,直径100~150 nm.通过X射线衍射仪(XRD)表征产物结构,扫描电镜(SEM)和透射电镜(TEM)表征产物形貌,X射线衍射能谱(XPS)、荧光光谱(PL)和震动样品磁强计(VSM)对产物组成化学态、发光性质和磁性进行表征分析.测试结果表明:制备产物为纯净CeO2,不存在其他杂质,产物晶格膨胀,晶格常数比理论值偏大,产物中存在氧缺陷和+3价铈离子;在室温情况下胶囊状CeO2具有铁磁性质,矫顽力(Hc)为170 Oe,饱和磁化强度(Ms)为0.081 emu/g,这个结果比一些磁性粒子掺杂CeO2的值要高;结合测试结果表明胶囊状纯净CeO2具有室温铁磁性是由于产物中氧空位与Ce^3+离子的存在引起的.

CeO2 samples have been synthesized by hydrothermal method using Ce(NO3)3.6H2O as cerium source,CO(NH2)2 as precipitant,PVP as surfactant and HNO3 as regulator to regulate the solution pH value.The CeO2is prepared by changing the dosage of urea.The capsule-like CeO2,200-300 nm in length and 100-150 nm in diameter,was synthesized when the amount of urea was 8 mmol.The structure and morphology,composition and chemical states,luminescence properties and magnetism of the capsule-like CeO2 were characterized and analyzed by X-ray diffractometer(XRD),Scanning electron microscopy(SEM),Transmission electron microscopy(TEM),X-ray diffraction energy spectrum(XPS),fluorescence spectrum(PL)and vibrating sample magnetometer(VSM).The XRD results indicated that CeO2 samples thus prepared were pure CeO2 without other impurities,the crystal lattice of the product expanded,and the crystal lattice constant larger than the theoretical value,and there existed oxygen defects and+3 valence cerium ions in the samples;the Capsule-like CeO2 was ferromagnetic at room temperature,saturation magnetization(Ms)was 0.081 emu/g and coercive force(Hc)was 170 Oe.Such a value was higher than some magnetic particles mixed with cerium dioxide;The results indicated that the presence of Ce^3+ions and the oxygen vacancy in the product caused the ferromagnetism of pure capsule-like CeO2 at room temperature.