Topotactic Routes to Layered Calcium Cobalt Oxides

Cushing, Brian L.

doi:10.1006/jssc.1998.7957

Cited by 100 publications

(84 citation statements)

References 40 publications

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“…The ceramic samples were prepared by the method described by Cushing and Wiley 11 . Stoichiometric amounts of Co metal and anhydrous NaOH were ground under Ar atmosphere and fired at 700ºC under flowing oxygen for a total of 5 days with intermediate grindings.…”

Section: Sample Chemistrymentioning

confidence: 99%

Chemical, structural, and transport properties ofNa1−xCoO2

2003

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We report measurement of room-temperature compressibility, thermal expansion, thermoelectric power α(T) at various pressures P ≤ 20 kbar, basal-plane resistivity ρ ab (T), magnetic susceptibility and thermal conductivity κ(T) taken on single-crystal or coldpressed Na 0.57 CoO 2 . An enhancement of a large α(T) with a change of slope occurs on heating near 100 K, but this enhancement is progressively suppressed by pressure P ≤ 20 kbar. The c-axis thermal expansion is large in the interval 150 K

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Section: Sample Chemistrymentioning

confidence: 99%

Chemical, structural, and transport properties ofNa1−xCoO2

2003

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“…The crystal structure of Na x CoO 2 (0.5 ≤ x ≤ 1) consists of two-dimensional CoO 2 layers of edge-sharing CoO 6 octahedra piled up along c-axis, and Na ions are inserted between CoO 2 layers with a trigonal prismatic (P) or octahedral (O) environment [4,5]. Depending upon the Na content, Na x CoO 2 crystallizes in to four different phases i.e.…”

Section: Introductionmentioning

confidence: 99%

Growth and morphology of the single crystals of thermoelectric oxide material Na_xCoO₂

Thinaharan

Aswal²,

Singh

et al. 2004

Cryst. Res. Technol.

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We have grown single crystals of recently discovered thermoelectric oxide material Na x CoO 2 using NaCl flux. Crystals of sizes upto 1.5 x 1.5 x 1.5 mm 3 having different morphological habits were reproducibly grown. The atomic force microscopic studies show that along c-axis crystals grow via 2D layer-by-layer mechanism. The X-ray diffraction analyses show that grown crystals are rich in Na content as compared to the starting charge indicating that NaCl flux also acts as a source of Na. The resistivity of the crystals exhibited a linear temperature dependence in the region between 30 and 300 K.

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“…The recent observations of superconductivity in Na 0.33 CoO 2 ·1.3H 2 O [5], charge ordering in Na 0.5 CoO 2 [6] and complex magnetic structures in Na x CoO 2 (x=0.67, 0.75) [7] have further heightened the interest in this kind of materials. Intercalation of divalent ions (Ca shows a Seebeck coefficient comparable to that of Na x CoO 2 [8]; partial substitution of Ca for Na in Na x CoO 2 also gave an enhancement in both Seebeck coefficient and electric resistivity [2,9]. Structural investigations revealed that the intercalations of either Na (Sr) atoms or H 2 O molecules could make the local structure very complex; the intercalated atoms can be random with high mobility or crystallized in certain ordered states [10].…”

Section: Introductionmentioning

confidence: 99%

Electronic structure and electron energy-loss spectra of Sr0.35CoO2

Xiao

Yang

et al. 2005

Solid State Communications

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The electronic structure of Sr 0.35 CoO 2 , structurally analogous to the layered Na x CoO 2 , has been evaluated using the local spin density approximation (LSDA). We find that evident c-dispersions appear in both the e ' g and a 1g Co-derived bands, demonstrating the existence of a notable interplanar interaction in Sr 0.35 CoO 2 . The LSDA+U calculation reveals that the electronic structure, in particular the band splitting between the spin-up and spin-down electrons, changes evidently along with the increase of the effective on-site Coulomb interaction U. Analysis of theoretical and experimental electron energy-loss spectra (EELS) for the oxygen K-edge and the Co L 23 -edge suggests that the on-site interaction (U) in Sr 0.35 CoO 2 is less than 3eV which is noticeably weaker than the estimated value (from 5eV to 8eV) in the Na x CoO 2 materials.

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Topotactic Routes to Layered Calcium Cobalt Oxides

Cited by 100 publications

References 40 publications

Chemical, structural, and transport properties ofNa1−xCoO2

Chemical, structural, and transport properties ofNa1−xCoO2

Growth and morphology of the single crystals of thermoelectric oxide material Na_xCoO₂

Electronic structure and electron energy-loss spectra of Sr0.35CoO2

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Topotactic Routes to Layered Calcium Cobalt Oxides

Cited by 100 publications

References 40 publications

Chemical, structural, and transport properties ofNa1−xCoO2

Chemical, structural, and transport properties ofNa1−xCoO2

Growth and morphology of the single crystals of thermoelectric oxide material NaxCoO2

Electronic structure and electron energy-loss spectra of Sr0.35CoO2

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Growth and morphology of the single crystals of thermoelectric oxide material Na_xCoO₂