Single crystal studies on Co-containing {tau}-borides Co{sub 23-x}M{sub x}B{sub 6} (M=Al, Ga, Sn, Ti, V, Ir) and the boron-rich {tau}-boride Co{sub 12.3}Ir{sub 8.9}B{sub 10.5}
- Albert-Ludwigs-Universitaet Freiburg, Institut fuer Anorganische und Analytische Chemie, Albertstr. 21, D-79104 Freiburg (Germany)
Single crystals of the cubic {tau}-Borides Co{sub 23-x}M{sub x}B{sub 6} (M=Al, Ga, Sn) were synthesised from the elements at temperatures between 1200 and 1500 deg. C. According to the structure refinements one (Ga, Sn: 8c) or two (Al: 4a and 8c) of the four independent metal sites show a mixed occupation Co/M resulting in the compositions Co{sub 20.9}Al{sub 2.1}B{sub 6}, Co{sub 21.9}Ga{sub 1.1}B{sub 6}, and Co{sub 21.4}Sn{sub 1.6}B{sub 6}, respectively. Melts with Indium gave access to Co{sub 23}B{sub 6} as the first binary {tau}-boride (Fm3-barm,a=10.4618(13) A, 104 refl., 14 param., R{sub 1}(F)=0.0132, wR{sub 2}(F{sup 2})=0.0210). With M=Ir mixed occupations occur for all sites and the boron content varies. The composition for the boron-poor single crystal was Co{sub 16.2}Ir{sub 6.8}B{sub 6}. A higher Ir-content enables the uptake of additional boron resulting in a composition Co{sub 12.3}Ir{sub 8.9}B{sub 10.5}. This can be explained be the substitution of metal atoms on the 8c-site by B{sub 4}-tetrahedra. A boron-rich phase was observed for the first time for a {tau}-boride of cobalt. All compositions were confirmed by EDX measurements. - Graphical Abstract: Single crystal investigations on {tau}-borides Co/M/B with M = Al, Ga, In, Sn, V, Ti, Ir explained the substitution processes. Furthermore the yielded the first binary boride, Co{sub 23}B{sub 6}, and a boron-rich Co{sub 12.3}Ir{sub 8.9}B{sub 10.5} containing B{sub 4}-tetrahedra.
- OSTI ID:
- 21212226
- Journal Information:
- Journal of Solid State Chemistry, Vol. 182, Issue 3; Other Information: DOI: 10.1016/j.jssc.2008.10.036; PII: S0022-4596(08)00536-7; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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