Vanadium Clustering/Declustering in P2鈥揘a1/2VO2 Layered Oxide

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• 作者：Marie Guignard ; Dany Carlier ; Christophe Didier ; Matthew R. Suchomel ; Erik Elka茂m ; Pierre Bordet ; Rodolphe Decourt ; Jacques Darriet ; Claude Delmas
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：February 25, 2014
• 年：2014
• 卷：26
• 期：4
• 页码：1538-1548
• 全文大小：581K
• 年卷期：v.26,no.4(February 25, 2014)
• ISSN：1520-5002

文摘

The new layered phase P2鈥揘a_1/2VO₂ has been synthesized by sodium electrochemical deintercalation. Its structure has been studied by high resolution powder diffraction, pair distribution function analysis, and nuclear magnetic resonance spectroscopy between 300 and 350 K. An increase of 2 orders of magnitude in its electronic conductivity has been observed at approximately 322 K, and a structural transition has been found to occur simultaneously. The arrangement of sodium ordering in P2鈥揘a_1/2VO₂, which maximizes sodium鈥搒odium distances to lower electrostatic repulsions between alkali ions, is found to be unchanged across this transition. At room temperature, high resolution powder diffraction and pair distribution function analysis reveal the triangular lattice formed by vanadium ions to be distorted by the formation of pseudotrimers clusters with vanadium鈥搗anadium distances as short as 2.581 脜. Above the transition, the pseudotrimers disappear and the triangular vanadium lattice becomes more regular with a mean vanadium鈥搗anadium distance of 2.88 脜. At 350 K, the increase in P2鈥揘a_1/2VO₂ electronic conductivity is due to enhanced charge transport resulting from the declustering of vanadium ions. These results highlight how sodium ordering between the MO₂ layers and the electronic transport within the MO₂ layers are intimately correlated in Na_xMO₂-type sodium-layered oxides.