Compositions and Chemical Bonding in Ceramics by Quantitative Electron Energy-Loss Spectrometry

Bentley, J.; Horton, L.L.; McHargue, C.J.; McKernan, Stuart; Carter, C.B.; Revcolevschi, A.; Tanaka, Satoru; Davis, R.F.

doi:10.1557/proc-332-385

Cited by 3 publications

(4 citation statements)

References 14 publications

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“…Moreover, the L 3 /L 2 intensity ratio is higher in CoO than in Co 3 O 4 , and a small shift to higher energies in Co 3 O 4 is observed, about 1.5 eV for L 3 and less than 1 eV for L 2 , although the Co L 2,3 ELNES is quite similar for these two phases. In CoO three small peaks (labeled by a, b, and c) are separated by 3 or 4 eV in the O-K edge whereas only two pronounced peaks (labeled by a and c peaks, and a small shoulder in between labeled by b) are present in Co 3 O 4 [2,4].…”

Section: Resultsmentioning

confidence: 99%

“…Owing to their diversified applications, Co oxides (periclase-CoO and spinel-Co 3 O 4 ) and their compounds have been widely and intensively investigated using various advanced electron microscopy and associated techniques [2][3][4][5][6][7][8][9]. Much attention was paid to EELS studies due to the sharp peaks of the Co-L ionization edge, which are known as white lines (caused by electron transitions from 2p 3/2 (L 3 edge) and 2p 1/2 (L 2 edge) core states to the unoccupied 3d states [3,10]), as well as to the sensitive variation of the O-K edge with composition, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Surface effects in the energy loss near edge structure of different cobalt oxides

Zhang

2007

Ultramicroscopy

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Surface effects in the energy loss near edge structure of different cobalt oxides

Zhang

2007

Ultramicroscopy

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“…To give an optimum estimation, a partially oxidized CoO specimen that contains CoO and Co 3 O 4 grain structure was chosen. 11 The CoO and Co 3 O 4 phases are separated by clear boundaries, and it is an ideal specimen for testing the optimum resolution. Similar EF-TEM experiments have been carried out using the Co-L and O-K edges.…”

Section: Resultsmentioning

confidence: 99%

Mapping the Valence States of Transition-Metal Elements Using Energy-Filtered Transmission Electron Microscopy

1999

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The properties of transition-metal oxides are related to the presence of elements with mixed valences, such as Mn and Co. Spatial mapping of the valence-state distribution of transition-metal elements is a challenge to existing microscopy techniques. In this letter, using the valence-state information provided by the white lines observed in electron energy-loss spectroscopy in a transmission electron microscope (TEM), an experimental approach is demonstrated to map the valence-state distributions of Mn and Co using the energyfiltered TEM. An optimum spatial resolution of ∼ 2 nm has been achieved for two-phase Co oxides with sharp boundaries. This provides a new technique for quantifying the valence states of cations in magnetic oxides.Many physical and chemical properties of inorganic materials are determined by the elements with mixed Valences in the structural unit, 1 by which we mean that an element has two or more different valences while forming a compound. Transitionand rare-earth-metal elements with mixed valences are unique for initiation of electronic, structural, and/or chemical evolutions. We have demonstrated previously the valence states of Mn and Co in their oxides by applying electron energy-loss spectroscopy (EELS) for quantitative determination. [2][3][4][5] In EELS, the L ionization edges of transition-metal, rare-earth, and actinide compounds usually display sharp peaks at the near-edge region. These threshold peaks are known as white lines. The unoccupied 3d states form a narrow energy band, the transition of a 2p-state electron to the 3d levels, leading to the formation of white lines observed experimentally. EELS experiments have shown that a change in the valence states of cations introduces significant variation in the intensity ratio of the white lines, giving the possibility of identifying the occupation number of 3d or 4d electrons (or cation valence states) using the measured white line intensities. 6,7 The information obtained using EELS is an integration over the spatial region illuminated by the incident electron beam. In this paper, we introduce a new experimental approach which can give the distribution maps of cation valences in real space, allowing a direct identification of cations with different valence states. This is useful for studying nanocomposite magnetic oxide materials with mixed valences. Figure 1a shows an EELS spectrum of MnO 2 acquired at 200 kV using a Hitachi HF-2000 transmission electron microscope equipped with a Gatan 666 parallel-detection electron energyloss spectrometer. The oxygen K edge and the Mn L edge are clearly seen. The two sharp peaks are the L 3 and L 2 white lines, the intensity ratio of which is very sensitive to the valance state of Mn. The sharp white lines are the dominant EELS fine structures of transition-and rare-earth-metal elements. EELS analysis of the valence state is carried out in reference to the spectra acquired from standard specimens with known cation valence states. If a series of EELS spectra are acquired from several standa...

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“…for volume compensation, and therefore affect the defect structure and the migration mechanisms across the Co 1−x O/ZrO 2 diffusion couples as experimentally proved for oxidized CoO-zirconia (CaO stabilized) eutectic [20] and Co 1−x O coating on zirconia (CaO stabilized) [21]. The abrupt change of oxygen concentration thus may account for the formation of Co 3−δ O 4 at the Co 1−x O/ZrO 2 interface.…”

Section: ••mentioning

confidence: 83%

On the nucleation and paracrystal interspacing of Zr-doped Co3−δO4

Shen

2004

Materials Science and Engineering: B

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A paracrystalline array of defect clusters was shown to form in Zr-doped Co 3−δ O 4 spinel in the ZrO 2 /Co 1−x O composites while prepared by a sintering route at 1650• C in air. Analytical electron microscopic observations indicated the spinel precipitate and its paracrystal predominantly formed at the ZrO 2 /Co 1−x O interface and the cleavages/dislocations of the Co 1−x O host. Defect chemistry consideration suggests the paracrystal is due to the assembly of charge-and volume-compensating defects of the 4:1 type with four octahedral vacant sites surrounding one Co 3+ -filled tetrahedral interstitial site. The interspacing of such defect clusters is 4.9 times the lattice spacing of the average spinel structure of Zr-doped Co 3−δ O 4 . This spacing between defect clusters is about 0.98 times that of our previously studied undoped Co 3−δ O 4 . There is much larger (3.4 times difference) paracrystalline spacing for Zr-doped Co 3−δ O 4 than its parent phase of Zr-doped Co 1−x O.

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Compositions and Chemical Bonding in Ceramics by Quantitative Electron Energy-Loss Spectrometry

Cited by 3 publications

References 14 publications

Surface effects in the energy loss near edge structure of different cobalt oxides

Surface effects in the energy loss near edge structure of different cobalt oxides

Mapping the Valence States of Transition-Metal Elements Using Energy-Filtered Transmission Electron Microscopy

On the nucleation and paracrystal interspacing of Zr-doped Co3−δO4

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