Ho4C7, Y4C7: Carbide mit C3 4-- und C4- -Ionen / Ho4C7, Y4C7: Carbides with C3 4- and C4- Ions

Abstract

Abstract The new compounds Ho4C7 and Y4C7 have been prepared by reaction of stoichiometric amounts of the metals and C in closed Ta capsules at 1450 and 1300 K. respectively. With HoF3 as a flux, black, needle like single crystals of Ho4C7 were obtained, which are air and moisture sensitive. Ho4C7 crystallizes in the space group P21/n (No. 14) with lattice constants a = 368.06(3), b = 1251.8(1). c = 1364.4(2) pm and β = 96.62(1)°. Y4C7 with a = 370.08(5), b = 1258.9(1), c = 1371.8(1) and β = 96.61(1)°. Two different kinds of carbon species occur in the two structures: isolated C4- ions and C3 4- units, respectively. The C4- ions are octahedrally surrounded by Ho-atoms. The Ho6C octahedra are condensed to form double chains parallel [100]. The chains are linked via C3 4- ions, which occupy positions above the edges of the Ho octahedra. Additional Ho atoms are located in voids between the C3 4- units. The compounds are electrically semiconducting. Ho4C7 has a magnetic Curie-Weiss behaviour with θ= -28(4) K and µeff= 8.8(2) µB.