Variation in Density and Colour of Cerium Oxide

Harwood, Margaret

doi:10.1038/164787a0

Cited by 9 publications

(5 citation statements)

References 1 publication

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“…More than a hemisphere of threedimensional data was collected using monochromatic Mo-Ka radiation, with frame widths of 2º in o and a counting time of 120 s per frame. The unit-cell parameters of the cerianite-(Ce) ( Table 3) are in general agreement with, but slightly larger than, those reported for synthetic CeO 2 by Goldschmidt and Thomassen (1923), Harwood (1949), Zintl and Croatto (1939), Brauer and Gradinger (1954) and Whitfield et al (1970). To our knowledge, the present work is the first single-crystal X-ray study of natural cerianite-(Ce).…”

Section: Single-crystal X-ray Diffraction Analysissupporting

confidence: 88%

Fluorine-, yttrium- and lanthanide-rich cerianite-(Ce) from carbonatitic rocks of the Kerimasi volcano and surrounding explosion craters, Gregory Rift, northern Tanzania

et al. 2011

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Cerianite-(Ce), ideally CeO2, occurs as rounded grains up to 5 μm across in a block of highly altered calcite carbonatite lava from the Kerimasi volcano, and as euhedral crystals up to 200 μm across in carbonatite-derived eluvial deposits in the Kisete and Loluni explosion craters in the Gregory Rift, northern Tanzania. X-ray powder diffraction data (a = 5.434(5) Å) and Raman spectroscopy (minor vibration modes at 184 and 571 cm—1 in addition to a strong signal at 449 cm—1) suggest the presence of essential amounts of large cations and oxygen vacancies in the Kisete material. Microprobe analyses reveal that the mineral contains both light and heavy trivalent rare earth elements (REE) (7.9-15.5 wt.% LREE2O3 and 4.9-9.7 wt.% HREE2O3), and that it is enriched in yttrium (7.1 — 14.5 wt.% Y2O3) and fluorine (2.2—3.5 wt.%). Single-crystal structure refinement of the mineral confirms a fluorite-type structure with a cation—anion distance of 2.3471(6) Å. The cerianite-(Ce) is considered to be a late-stage secondary mineral in the carbonatitic rocks.

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Section: Single-crystal X-ray Diffraction Analysissupporting

confidence: 88%

Fluorine-, yttrium- and lanthanide-rich cerianite-(Ce) from carbonatitic rocks of the Kerimasi volcano and surrounding explosion craters, Gregory Rift, northern Tanzania

et al. 2011

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“…The Fourier transforms of the EXAFS spectra of CeO 2 and some samples are representatively shown in Figure . The EXAFS spectrum of CeO 2 (Figure a) as the standard compound was analyzed by using theoretical parameters, and it was confirmed that the Ce−oxygen shell was fitted well with a single Ce−O bond ( R = 2.343 Å, N = 8) while the Ce−cation shell was fitted well with a single Ce−Ce bond ( R = 3.826 Å, N = 12), in good agreement with the reported CeO 2 structure 10 Fourier transforms of k 3 -weighted EXAFS spectra of CeO 2 (a), Ce(2)/SiO 2 (b), Ce(5)/Al 2 O 3 (c), Ce(0.01)/SiO 2 (d), and Ce(0.1)/Al 2 O 3 (e) samples treated under an oxidative atmosphere at 773 K. …”

Section: Resultssupporting

confidence: 78%

“…The EXAFS spectrum of CeO 2 (Figure 10a) as the standard compound was analyzed by using theoretical parameters, 40 and it was confirmed that the Ce-oxygen shell was fitted well with a single Ce-O bond (R ) 2.343 Å, N ) 8) while the Ce-cation shell was fitted well with a single Ce-Ce bond (R ) 3.826 Å, N ) 12), in good agreement with the reported CeO 2 structure. 52 Using the same parameters, the experimentally obtained EXAFS spectra were well fitted in the case of the supported ceria samples with high loading amount of Ce, such as Ce(2)/ SiO 2 (Figure 10b) and Ce(5)/Al 2 O 3 (Figure 10c). The fitting results showed that the Ce-O shell of these samples showed slightly lower distance ca.…”

Section: Resultsmentioning

confidence: 75%

Nonoxidative Coupling of Methane over Supported Ceria Photocatalysts

et al. 2008

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Various silica-supported rare earth oxides were examined for photocatalytic methane conversion around room temperature. Among them, silica-supported cerium oxide with low loading amount showed the highest photoactivity for nonoxidative coupling of methane (NOCM) to produce both ethane and hydrogen. XANES, DR UV−vis, and phosphorescence spectra of silica-supported cerium oxide revealed that the main species on the low loading samples were highly dispersed Ce(III) oxides, suggesting that they were the photocatalytic active sites for the reaction. The highly dispersed Ce(III) oxides could be formed also on alumina, which enhanced the photoactivity of alumina for the NOCM.

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“…Thus Bruno (75) and also Rienacher and Birchenstredt (342) have prepared compositions from Ce02 to CeOi.85 and have found only a single phase with the CaF2 structure. Harwood (191) has shown that ceric oxide preparations of varying colors all have the fluorite structure. McCullough (296) has shown that Y203 (Mn203 type) is completely miscible with Ce02 (CaF2 type).…”

Section: Boron-aluminum Group Oxidesmentioning

confidence: 99%