Partially Anion-Ordered Cerium Niobium Oxynitride Perovskite Phase with a Small Band Gap
Partially Anion-Ordered Cerium Niobium Oxynitride Perovskite Phase with a Small Band Gap
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DOI：
10.1021/acs.chemmater.1c00631
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发表时间：
2021-06
影响因子：
8.6
通讯作者：
Z. Shen;Ji Wu;Matthew W. Shorvon;G. Cazaux;S. C. Parker;S. Skinner
中科院分区：
文献类型：
--
作者：
Z. Shen;Ji Wu;Matthew W. Shorvon;G. Cazaux;S. C. Parker;S. Skinner
采用热氨解法合成了一种新型的黑色物相--铈铌氧氮化物（CeNb（O，N）3），并对其晶体结构和物理化学性质进行了研究。粉末X射线衍射和中子衍射证实了钙钛矿结构的CeNbO_（1.49（7）N_（1.51（7）））晶体是正交晶系，晶胞参数为a = 5.7137（5）N，B= 8.0567（5）N，c= 5.7209（5）N，呈现部分有序的阴离子排列。通过X射线光电子能谱证实了氮掺入到氧亚晶格中。该材料在空气中高温下的复杂多阶段氧化还原过程，包括200 °C以上的完全非晶化，650 °C下的重结晶，950 °C下的分解，以及最终氧化成化学计量的氧化铈铌CeNbO 4，通过同步热分析和原位X射线粉末衍射观察到。通过紫外-可见光谱研究了氮氧化物材料的带隙，由于氮掺入到氧亚晶格中，观察到前体氧化物CeNbO 4 +δ的Eg = 2.67 eV显著降低到Eg = 1.79 eV。通过密度泛函理论的模拟进一步证实，与完全有序（层状）结构（1.22 eV）相比，部分有序的阴离子排列加宽了带隙（1.78 eV）并稳定了结构。
A new phase of black color, cerium niobium oxynitride with general formula CeNb(O,N)3, was synthesized by thermal ammonolysis, and its crystal structure and physical and chemical properties are investigated. Powder X-ray and neutron diffraction has confirmed the perovskite-structured CeNbO1.49(7)N1.51(7)phase crystallized with the orthorhombicPnmasymmetry with unit cell parameters ofa= 5.7137(5) Å,b= 8.0567(5) Å,c= 5.7209(5) Å, presenting a partially ordered anionic arrangement. The incorporation of nitrogen into the oxygen sublattice was confirmed by X-ray photoelectron spectroscopy. Complex multistage redox processes of this material at elevated temperatures in air, including full amorphization above 200 °C, recrystallization at 650 °C, decomposition at 950 °C, and a final oxidation into the stoichiometric cerium niobium oxide CeNbO4, were observed by simultaneous thermal analysis and in situ X-ray powder diffraction. The band gap of the oxynitride material was investigated by UV–vis spectroscopy and, due to the incorporation of nitrogen into the oxygen sublattice, a significant decrease fromEg= 2.67 eV for the precursor oxide CeNbO4+δtoEg= 1.79 eV was observed. The simulation by density functional theory further confirms that the partially ordered anionic arrangement widens the band gap (1.78 eV) and stabilizes the structure compared to the completely ordered (layered) structure (1.22 eV).