Anion rearrangements in fluorinated Nd2CuO3.5статья

Статья опубликована в высокорейтинговом журнале

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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.

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[1] Anion rearrangements in fluorinated nd2cuo3.5 / G. Corbel, J. P. Attfield, J. Hadermann et al. // Chemistry of Materials. — 2003. — Vol. 15, no. 1. — P. 189–195. Nd2CuO3.5, a derivative of Nd2CuO4 with anion-deficient (CuO1.5square0.5) layers, has been fluorinated with XeF2 at temperatures between 100 and 400 C. Samples fluorinated at 200300 C exhibit superconductivity with critical temperatures of 6-11 K. Electron microscopy investigations revealed a complicated microstructure in both the initial and fluorinated phases. Nd2CuO3.5 is characterized by the presence of numerous twins which are caused by the lowering of the symmetry after a topotactic oxygen removal from the parent Nd2CuO4 phase. Fluorination at 200 C leads to an increase of the formal copper valence and to a restoration of the T'-type structure. It is suggested that fluorine replaces oxygen in the Nd2O2 slab and the released oxygen atoms migrate into the (CuO1.5square0.5) layers thus forming conducting (CuO2) planes. This rearrangement shows a close resemblance to that previously found in fluorinated A(2)CuO(3) (A = Ca, Sr). Local areas of fluorinated phases with larger values of the c parameter were found in the matrix of T' phase. At 300 C the monoclinic Nd2Cu(O,F)(5) phase is also formed (a approximate to 13.2 Angstrom, b approximate to 5.5 Angstrom, c approximate to 5.8 Angstrom, beta approximate to 92degrees, space group C2/c) with a chainlike ordering of the empty and filled anion positions in the Nd-2(O,F)(3) blocks and buckled (CuO2) planes due to a tilt of the Cu(O,F)(6) octahedra. [ DOI ]

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