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Please use this identifier to cite or link to this item: http://ir.ncue.edu.tw/ir/handle/987654321/14120

Title: Synthesis and Characterization of Layered Sodium Cobaltates
Authors: Liu, Chia-Jyi
Contributors: 物理學系
Date: 2011
Issue Date: 2012-09-10T06:12:20Z
Publisher: Nova Science Publishers
Abstract: The layered sodium cobaltates -NaxCoO2 show low electrical conductivity and large thermopower. These features are required for candidate materials in thermoelectric applications. Superconductive sodium cobalt oxyhydrates can be obtained by topotactic transformation of -NaxCoO2 via oxidative de-intercalation and hydration. This chapter presents the synthesis of -Na0.7CoO2 in the form of sol-gel bulk, films, nanotubules and submicron tubules. Materials characterization of -NaxCoO2 and cobalt oxyhydrates will be also presented. According to thermopower analysis, band narrowing is observed when -Na0.7CoO2 is transformed to potassium sodium cobaltoxyhydrates. According to the Co K-edge x-ray absorption spectra, the Co oxidation number for bi-layer hydrate Na0.33K0.02(H2O)1.33CoO2 is higher than that of mono-layer hydrate Na0.07K0.21 (H2O)0.63CoO2 with a chemical shift of 3.5 eV, which is in sharp contrast with Co K-edge x-ray absorption spectroscopy and cerimetric titration results for Nax(H2O)yCoO2, where there is essentially no difference of the oxidation number of Co between bi-layer and mono-layer sodium cobalt oxyhydrates.
Relation: 收錄於由 Lucas J. Vidmar 主編「Cobalt: Characteristics, Compounds and Applications」, Chapter 11: 227-262
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