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New Ternary Boride Carbides RE 10 B 9+ x C 10– x ( RE = Gd, Tb; x ≈︁ 0.2): Infinite Boron Carbon Branched Chains
Author(s) -
Babizhetskyy Volodymyr,
Hiebl Kurt,
Mattausch Hansjürgen,
Simon Arndt
Publication year - 2010
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200900489
Subject(s) - terbium , crystallography , monoclinic crystal system , crystal structure , materials science , ternary operation , octahedron , carbide , chemistry , metallurgy , optoelectronics , luminescence , computer science , programming language
Abstract New ternary rare earth metal boride carbides with compositions close to RE 10 B 9 C 10 ( 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 P 2 1 / c , a = 7.937(1), b = 23.786(2), c = 11.172(1) Å, β = 133.74(1)°, Z = 4, R 1 = 0.045 ( wR 2 = 0.11) for 5713 reflections with I o > 2σ( I o ). In the structure BC 2 units and single carbon atoms are attached to a zigzag boron chain forming the unprecedented B 18 C 18 branching unit with a B–B distance of 2.42(2) Å 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 2 fragments can be rationalized in terms of a slight deviation in stoichiometry, Tb 10 B 9+ x C 10– x ( x ≈ 0.2). The terbium compound is ferromagnetic below T C ≈ 45 K. Due to the presence of moderately narrow domain walls the magneto‐crystalline energy is small.