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[M] Novel ternary Y-B-C compound: Y10+xB7C10-x (x ≈ 0.1) オンラインリソース

著者: (出版日: 2009-07-24)

コレクション: NIMS成果物
形態: オンラインリソース オンラインリソース
言語: 不明
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A novel ternary Y-B-C compound Y10+xB7C10−x is established. Y10+xB7C10−x has a monoclinic crystal structure with space group C2/c (No.15) and lattice constants a = 1.1273(14) nm, b = 1.1159(14) nm, c = 2.3566(30) nm and beta = 98.15(2) . Y10+xB7C10−x crystal rods were grown by floating zone technique and consisted of a predominant crystal phase and impurity phases. A small crystal having sufficient quality for single crystal XRD analysis could be selected. Structure refinement achieved a final R1 = 0.044 for 1660 independent reflections with Fo > 4 (Fo). 10 Y sites, 8 B sites, 9 C sites and one C/Y mixed occupancy site with about 0.9/0.1 occupation ratio were assigned. The unit chemical formula is Y10+xB7C10−x (x 0.1), and the unit cell contains 8 formula units. Y10+xB7C10−x has a layer structure: Y-C double layers, in which Y and C bond alternatively like in the NaCl structure, spread parallel to the (001) plane and stack along the c-axis. The Y-C double layer is connected to the neighboring Y-C double layers via C-B-C chains or C-B-B-C chains. This structure was confirmed by electron diffraction and high-resolution electron microscopy. Magnetic susceptibility measurement indicated that the Y10+xB7C10−x phase has no superconductivity above 2 K. A minor superconducting phase with Tc=7.5 K was observed, but ascribed to an unidentified impurity phase.