Oxygen nonstoichiometry and the origin of Na ion ordering in P2-Na(x)CoO(2)
Resource
PHYSICAL REVIEW B, 82(5), 054106
Journal
Physical Review B
Pages
54106
Date Issued
2010
Date
2010
Author(s)
Abstract
The impact of oxygen deficiency on physical properties of Na2/3 CoO2-δ has been investigated. From the combined thermogravimetric, magnetic susceptibility, and synchrotron x-ray Laue diffraction studies, it is demonstrated that Na2/3 CoO2 shows no superlattice ordering due to Na ions; however Na2/3 CoO 1.98, which has the same Co valence as that of Na0.71 CoO2, shows nearly identical magnetic and transport properties and the same simple hexagonal superlattice ordering of √ 12 a. It is proposed that the Na ion ordering found in Na2/3 CoO1.98 is identical to the ideal Na0.71 CoO2 of large √ 12 a×√ 12 a×3c superlattice but with additional Na vacancies which are bound to the oxygen defects at room temperature. We conclude that oxygen vacancies play a key role in stabilizing the superlattice structure and must be accounted for in its modeling. © 2010 The American Physical Society.
Type
journal article
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