Influence of cooling rate on the structure and composition of NaxCoO2 (x ∼ 0.65)

The influence of cooling rate on the composition, structure and magnetic behaviour of NaxCoO2 (x~ 0.65) is reported. Slow cooled and quenched samples are shown to have different compositions: x = 0.63 and x = 0.68, respectively. On slow cooling, exsolution of sodium occurs and appears as a separate...

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Bibliographic Details
Published in:Journal of materials chemistry 2009-01, Vol.19 (8), p.1123-1128
Main Authors: TONG ZHOU, DOU ZHANG, BUTTON, Tim W, WRIGHT, Adrian J, GREAVES, Colin
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Inorganic compounds
Neutron diffraction and scattering
Physics
Single-crystal and powder diffraction
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
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Summary:The influence of cooling rate on the composition, structure and magnetic behaviour of NaxCoO2 (x~ 0.65) is reported. Slow cooled and quenched samples are shown to have different compositions: x = 0.63 and x = 0.68, respectively. On slow cooling, exsolution of sodium occurs and appears as a separate phase, Na2CO3. Whereas the slow-cooled sample has the expected hexagonal symmetry, P63/mmc, a distortion to orthorhombic symmetry (Cmcm, a = 2.83333(4) A, b = 4.92297(7) A, c = 10.8948(2) A) is observed for the quenched material. High resolution neutron powder diffraction reveals displacement of sodium ions from their ideal positions for both materials. The different structure and composition are reflected in the Raman spectra and magnetic behaviour of the phases.
ISSN:0959-9428
1364-5501
DOI:10.1039/b813612b