New Ternary Boride Carbides RE10B9+xC10-x (RE = Gd, Tb; x approximate to 0.2): Infinite Boron Carbon Branched Chains

作者：Babizhetskyy Volodymyr^*; Hiebl Kurt; Mattausch Hansjuergen; Simon Arndt

来源：Zeitschrift fur Anorganische und Allgemeine Chemie, 2010, 636(7): 1229-1235.

DOI：10.1002/zaac.200900489

• Rare earths
• Borocarbides
• Magnetic properties
• X-ray diffraction
• Ternary compounds

New ternary rare earth metal boride carbides with compositions lose to RE10B9C10 (RE = Gd, Tb) were prepared from the elements by melting around 1800 K followed by annealing in silica tubes at 1270 K for one month. The crystal structure of the terbium compound was solved by single-crystal X-ray diffraction. It crystallizes in a new structure type in the monoclinic space group P2(1)/c, a = 7.937(1), b = 23.786(2), c = 11.172(1) angstrom, beta = 133.74(1)degrees, Z = 4, R1 = 0.045 (wR2 = 0.11) for 5713 reflections with I-o > 2 sigma(I-o). In the structure BC, units and single carbon atoms are attached to a zigzag boron chain forming the unprecedented B18C18 branching unit with a B B distance of 2.42(2) angstrom between these units. In addition isolated carbon atoms occupy the centres of elongated octahedra formed by rare earth metal atoms. Disorder in the terbium position together with anomalous displacement ellipsoids for carbon atoms except of those in the BC, fragments can be rationalized in terms of a slight deviation in stoichiometry, Tb(10)B(9+x)4,C10-x., (x approximate to 0.2). The terbium compound is ferromagnetic below Tc 45 K. Due to the presence of moderately narrow domain walls the magneto-crystalline energy is small.

• 出版日期2010