Low-Temperature Synthesis and Electric Properties of New Layered Cobaltite, SrxCoO2

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

“…Fig. 2 [8,11] in agreement with the half-metallic band structure as illustrated in fig.1. antiferromagnetic spin correlations above 50K [11].…”

“…Structural analysis by means of transmission-electron microscopy and x-ray diffraction suggested that the well-defined Sr-ordered state only appears at x ≅ 1/3 in Sr x CoO 2 (0.25≤x≤0.4) system [11] The crystal structure of Sr 0.35 CoO 2 used in our calculation was based on the x-ray diffraction result as reported by R. Ishikawa et al [8]. This phase has the lattice parameters of a=2.820Å and c=11.525Å with the space group of P6 3 /mmc.…”

“…Polycrystalline materials of Sr 0.35 CoO 2 were prepared by the low-temperature ion exchange reaction from theγ-Na 0.7 CoO 2 precursor prepared by conventional solid-state reaction [8,11]. The measurements of EELS were performed on a Tecnai F20 transmission electron microscope equipped with a post column Gatan imaging filter.…”

“…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].…”

Thermoelectric Properties of the Layered Cobaltite Ca<SUB>3</SUB>Co<SUB>4</SUB>O<SUB>9</SUB> Epitaxial Films Fabricated by Topotactic Ion-Exchange Method

“…Recently, p-type layered cobalt oxides including Na x CoO 2 (x ¼ 0:3 $ 1), 2,3) Sr x CoO 2 (x $ 0:35) 4,5) and Ca 3 Co 4 O 9 , [6][7][8] have attracted much attention toward the realization of oxide TE devices because of their good TE performance and advantages over state-of-the-art, high temperature TE materials, including a SiGe-based alloy 9) and -FeSi 2 , 10,11) in terms of chemical and thermal resistances at high-temperatures ($ 1000 K) and low toxicity. Among the layered cobalt oxides, Ca 3 Co 4 O 9 is regarded as a most promising material since it can exhibit good thermal stability at 1000 K in air.…”