烧绿石型富氧相Ce_2Zr_2O_8与缺氧相Nd_2Zr_2O_7的振动光谱及XPS对比研究

Vibrational Spectrum and XPS Contrastive Studies on Pyrochlore-Type Oxygen-Rich Ce_2Zr_2O_8 and Oxygen-Defective Nd_2Zr_2O_7 Phases

采用石墨还原法成功制备了富氧相Ce2Zr2O8,选用缺氧相Nd2Zr2O7替代其前驱体CeZrO3.5+δ进行结构对比分析,利用X射线衍射(XRD)、拉曼光谱(Raman)、红外光谱(IR)及X射线光电子能谱(XPS)对样品体、表晶体结构进行表征。XRD结果表明,Ce2Zr2O8相具有典型烧绿石结构特征,表征Ce/Zr阳离子有序排列的超结构峰非常明显,但其Zr—O配位体由前驱体中的[ZrO6]八面体转变为[ZrO8]立方体,[ZrO8]配位体形成大大降低了Ce2Zr2O8的结构稳定性。Raman和IR结果表明,Ce2Zr2O8相的振动光谱谱带比其前驱体替代物Nd2Zr2O7显著增多,说明氧离子的富集导致Ce2Zr2O8相中某些振动简并峰消除简并,该结果进一步证实了其结构对称性较前驱体更低。XPS结果表明,Ce2Zr2O8相表面Ce(Ⅳ)特征峰(916.3eV)非常明显,没有Ce(Ⅲ)特征峰(885eV)出现,说明该相前驱体中的Ce3+已被完全氧化成Ce4+;Ce2Zr2O8相中Zr(3d)结合能与萤石相Gd1.2U0.8Zr2O7+y接近证实其表面形成了与体相一致的[ZrO8]配体;O(1s)低位结合能升高表明Ce2Zr2O8体相氧种介于晶格氧和吸附氧之间,高位氧峰出现说明其表面含有吸附氧,吸附氧与Ce2Zr2O8体相结合强度介于CeO2和Nd2Zr2O7之间。

Pyrochlore-type oxygen-rich Ce2 Zr2 O8 phase was prepared successfully by graphite reduction method. With the oxy-gen[U8]-defective Nd2 Zr2 O7 substituting for the oxidized precursor phase CeZrO3. 5＋δwas carried out the structure comparative analysis with Ce2 Zr2 O8. The X-ray diffraction （XRD）,Raman spectroscopy （Raman）,infrared spectroscopy （IR）and X-ray photoelectron spectroscopy （XPS）were used to characterize the crystal structure of samples. The XRD experimental results show that Ce2 Zr2 O8 bulk phase contains the typical structure of pyrochlore,the superstructure peaks that characterize Ce/Zr cations ordering arrangement are very obvious,but the Zr-O ligands had also transformed from octahedrons of the co-top connection in the precursor to cubes of co-edge connection in the Ce2 Zr2 O8 ,and the formation of [ZrO8 ]ligand reduced greatlly the structural stability of Ce2 Zr2 O8 phase. Raman and IR results show that vibrational spectra bands of Ce2 Zr2 O8 phase increased significantly, meaning that the enriched oxygen ions result in a removal of the degeneracy peak for Ce2 Zr2 O8 phase,which confirms further the structural symmetry of Ce2 Zr2 O8 phase lower than its precursor. XPS results show that Ce （Ⅳ）characteristic peak （9 1 6. 3 eV） in the Ce2 Zr2 O8 phase surface is very obvious. No the appearance of Ce （Ⅲ）peak （885 eV）suggests that Ce3＋ from the precur-sor has been completely oxidized into Ce4＋ in the Ce2 Zr2 O8 phase;the Zr （3d）binding energy is close to fluorite phase with Zr4＋,which confirms that [ZrO8 ]ligand in the Ce2 Zr2 O8 surface is consistent with the bulk phase. The increasing low binding energy of O（1s）shows that oxygen species in the Ce2 Zr2 O8 bulk phase are between lattice oxygen and adsorbed oxygen,the presence of high oxygen peak suggests that the surface of Ce2 Zr2 O8 contains adsorbed oxygen,and the bonding strength between adsorption oxygen and Ce2 Zr2 O8 bulk phase is between CeO2 and Nd2 Zr2 O7.