期刊
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
卷 16, 期 7, 页码 3274-3281出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c3cp54613f
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资金
- National Science Council of Taiwan, Republic of China [NSC 1002112- M-011-002-MY3, NSC 100-2911-I-213-501-MY2]
- French Ministeres des Affaires Etrange` res (MAE) et de l'Enseignement Superieur et de la Recherche (MESR) [25253UF, DILUMAGOX 12-IS10-0002-01]
Dopant-induced structural differences and defects in Sm doped CeO2 nanoparticles (NPs) exhibiting room temperature ferromagnetism were investigated by complementary spectroscopic analysis, including X-ray Absorption Spectroscopy, Extended X-Ray Absorption Fine Structure analysis, Raman spectroscopy and atomically resolved Scanning Transmission Electron Microscopy-Electron Energy Loss Spectroscopy (STEM-EELS). The CeO2 NPs were prepared by precipitation methods with Sm/Ce ratios ranging from 0 to 0.17 and with typical sizes from 2 to 4 nanometers. These results demonstrated that the nature and the distributions of defects strongly depend on the concentrations of the dopants. Two regimes in the formation of these (Ce1-x, Sm-x) O2-delta NPs were observed. At lower dopant levels (x < 7%), Sm3+ atoms mainly replace the Ce atoms in the (Ce3+-O2- vacancy) complexes which are present in ceria NPs. The dopants are unambiguously observed and localized as diluted by real space STEM-EELS spectromicroscopy done with atomic sensitivity. Nevertheless, this substitution induces a strong structural rearrangement and some Sm dopants are also observed as interstitials in association with Ce vacancies. At higher doping concentrations (x > 7%), a Sm rich phase in association with a high amount of oxygen vacancies is observed at the surface of the particles. It results in the formation of core-shell type nanoparticles with crystallographic continuities where a Sm doped CeO2-delta core is surrounded by a layer of typical (Ce-0.7, Sm-0.3)(2)O-3 composition.
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