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The Rare Earth CarbidesR4C5withR=Y, Gd, Tb, Dy, and Ho

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Abstract

The five carbidesR4C5(R=Y, Gd–Ho) have been prepared by arc-melting cold-pressed pellets of the elemental components and subsequent annealing at 1050°C. They crystallize with a new orthorhombic structure type (Pbam,Z=2), which has been determined from X-ray powder diffractometer data of Y4C5(a=657.35(9) pm,b=1191.8(1) pm,c=366.92(5) pm,RF=0.035 for 179 structure factors) and also refined from powder data of Tb4C5(a=660.8(1) pm,b=1197.3(2) pm,c=368.71(6) pm,RF=0.035 for 181Fvalues) and Ho4C5(a=653.00(8) pm,b=1184.6(1) pm,c=363.80(4) pm,RF=0.036 for 171Fvalues and 10 positional parameters each). The structure contains building blocks, which were also found in the two closely related structures ofα- andβ-Ho4C7. One-fifth of the carbon atoms are isolated from each other and coordinated octahedrally by rare earth atoms. The other carbon atoms form pairs with C–C bond distances of 133.5(15), 136(3), and 129(2) pm in Y4C5, Tb4C5, and Ho4C5, respectively, corresponding to C–C double bonds. Hence, all valence electrons can be accommodated in bonding R–C and C–C states according to the formula (R+3)4(C−42)2C−4, where the superscripts represent oxidation numbers. Nevertheless, the hydrolyses of Y4C5and Ho4C5with distilled water resulted in up to 41 wt% ethane, up to 16 wt% propane and propene, and up to 18 wt% higher hydrocarbons in addition to the expected products methane and ethylene.

References (19)

  • J. Bauer et al.

    J. Less-Common Met.

    (1985)
  • F.H. Pollard et al.

    J. Chromatogr.

    (1964)
  • W. Jeitschko et al.

    J. Less-Common Met.

    (1989)
  • R. Pöttgen et al.

    Inorg. Chem.

    (1991)
  • H. Mattausch et al.

    Z. Naturforsch. B

    (1994)
  • R. Czekalla et al.

    Z. Naturforsch. B

    (1996)
  • E.K. Storms

    High Temp. Sci.

    (1971)
  • R. Czekalla et al.

    Z. Kristallogr. Suppl.

    (1995)
  • J.W. Visser

    J. Appl. Crystallogr.

    (1969)
There are more references available in the full text version of this article.

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    Temperature of βHoCx ↔ αHo2Cx transformation needs additional investigation. Ho4C5 compound was synthesized only after long-term annealing of the as-cast alloys with the atomic ratio Ho:C = 48:52 for 40 days at 1050°C [13]. In the alloy with slightly off the ideal composition 4:5, a bcc Ho3C as the impurity phase was detected.

  • New ternary rare-earth metal boride carbides R<inf>15</inf>B <inf>4</inf>C<inf>14</inf> (R=Y, GdLu) containing BC<inf>2</inf> units: Crystal and electronic structures, magnetic properties

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    At the metal rich side defect NaCl-type carbides are known with compositions around R3C, R2C and R4C5. Single carbon atoms are located in octahedral lanthanoid voids in R3C, in R2C, and R4C5 structures, single carbon atoms coexist with C2 pairs [1,2]. Several compounds with higher carbon contents have been previously reported with the approximate composition R15C19 [3–8], and they were later established for R=Sc, Ho–Lu as the Sc3C4-type structure [9] with three different kinds of carbon species: isolated carbon atoms, C2 and C3 units, respectively.

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