Hydrothermal synthesis and electronic properties of FeWO4 and CoWO4 nanostructures
Hydrothermal synthesis and electronic properties of FeWO4 and CoWO4 nanostructures
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DOI：
10.1016/j.jallcom.2009.12.099
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发表时间：
2010-03
影响因子：
6.2
通讯作者：
S. Rajagopal;D. Nataraj;O. Khyzhun;Y. Djaoued;J. Robichaud;D. Mangalaraj
中科院分区：
文献类型：
--
作者：
S. Rajagopal;D. Nataraj;O. Khyzhun;Y. Djaoued;J. Robichaud;D. Mangalaraj
以钨酸钠(Na2WO4·2H2O)、硫酸亚铁铵[(NH4)2Fe(SO4)2·6H2O]和氯化钴(CoCl2·6H2O)溶液为前驱体，采用水热法制备了钨酸铁(FeWO4)和钨酸钴(CoWO4)纳米结构。用X射线衍射仪和透射电子显微镜对所制备的钨酸盐的晶体结构和形貌进行了表征。上述表征表明，所得产物属于单斜晶系和P2/a空间群，FeWO4和CoWO4的纳米颗粒平均尺寸分别约为150 nm和70 nm。用X射线光电子能谱(XPS)、X射线发射能谱(XES)和X射线吸收能谱(XAS)对FeWO4和CoWO4钨酸盐的电子性质进行了研究。记录了XPS价带和核能级光谱、XAS W LII边(未占据的类W d态)以及反映类W d和O p价态能量分布的XES带。XPS和XAS结果表明，所制备的FeWO4和CoWO4钨酸盐的组成接近化学计量比。XES结果表明，类W5d态和类O2p态对FeWO4和CoWO4钨的整个价带区域都有贡献，但类O2p态的贡献最大出现在价带的上部，而类W5d态的贡献则分别出现在价带的下部。
Iron tungstate (FeWO4) and cobalt tungstate (CoWO4) nanostructures were prepared by the hydrothermal method using sodium tungstate (Na2WO4·2H2O), ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] and cobalt chloride (CoCl2·6H2O) solutions as precursors. The crystal structure and morphology of the as-prepared tungstates were characterized by X-ray diffraction analysis and transmission electron microscopy. The above characterizations render that the products obtained belong to the monoclinic crystal system and P2/a space group, with average sizes of nanoparticles of about 150nm and 70nm in the case of FeWO4and CoWO4, respectively. Electronic properties of the FeWO4and CoWO4tungstates were studied using several X-ray spectroscopy methods, mainly X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS). The XPS valence-band and core-level spectra, the XAS W LIIIedges (unoccupied W d-like states) as well as the XES bands reflecting the energy distribution of the valence W d- and O p-like states were recorded. The present XPS and XAS results reveal that the as-prepared FeWO4and CoWO4tungstates are in a composition close to a stoichiometric one. The XES results render that the W 5d- and O 2p-like states contribute throughout the whole valence-band region of the FeWO4and CoWO4tungstates, however maximum contributions of the O 2p-like states occur in the upper, whilst the W 5d-like states in the lower portions of the valence band, respectively.