Oxygen vacancy‐induced microstructural changes of annealed CeO_2−xnanocrystals

Abstract

Nanocrystalline ceria (CeO 2 ) is known for its ionic conductivity and oxygen storage properties, which depend on the presence of oxygen ion vacancies. The vacancies cause several important changes in CeO 2 involving microstrain, electronic structure, magnetic properties, etc. In this article, we focus our attention to the microstructural changes of nanocrystalline CeO 2−x annealed at different temperatures in the range 200-500 • C. Structural and vibrational properties were investigated by X-ray diffraction and Raman spectroscopy. It was observed that the content of oxygen vacancies changed significantly with increasing annealing temperature, which plays an important role in the observed microstructural changes of the annealed samples. We demonstrate that the observed microstrain changes, because of variable defect content, dominate over the crystallite size effect. This finding is opposite to the conclusions made by several other authors. A new mode, classified as a probable surface mode, was observed in the Raman spectra at ∼480 cm −1 , the appearance of which can be explained by the large defective structure and disorder in the ceria lattice.

Oxygen vacancy and Ce3+ ion dependent magnetism of monocrystal CeO2 nanopoles synthesized by a facile hydrothermal method

“…(8) has been compared with the stoichiometry determined directly from the intensities of the O 1s and Ce 3d XPS peaks. The A O and A Ce are corresponding to the peak area of O 1s and Ce 3d respectively.…”

“…CeO 2 is a chemically stable oxide, with an outstanding capacity to store or release oxygen due to the variation of the oxidation state of cerium between +3 and +4 [8]. Because the variation of the oxidation state can lead to oxygen vacancies and Ce 3+ ions, hence, this property can contribute to novel properties.…”

Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

“…These oxygen vacancies play an important role to produce magnetism in the oxide nanomaterials. 20,21 Coey et al have suggested that the oxygen vacancies can make a significant contribution to enhance the ferromagnetism by changing the band structure of host oxides. 22 Sundaresan et al 17 have explained the ferromagnetism in CeO 2 NPs in terms of exchange interactions between unpaired spins resulting from oxygen vacancies.…”

In situ Raman characterization of CeO2 thin films sputtered on (111) Si in order to optimize the post growth annealing parameters

“…The possibility of the reversible transition from CeO 2 to Ce 2 O 3 makes cerium oxide one of the promising materials, the desired catalytic properties of which can be adjusted by a suitable choice of metal or metal oxide additives. In fact, the substitution of a part Ce 4+ by other suitable cations improves the low temperature reducibility and the oxygen storage capacity of cerium oxide [19]. However, CeO 2 may also be useful for radiation dosimeters [20,21] because nuclear radiations modify the electrical properties of CeO 2 film structures.…”