Sc2B1.1C3.2, a new rare-earth boron carbide with graphite-like layers

A Sc-based boron carbide Sc2B1.1C3.2 with a two-dimensional graphite-like f ramework has been synthesized by a solid state chemical reaction route. Cry stals have been grown successfully and the crystal structure could be assig ned to represent a new structure type of rare-earth boron carbides. The tri gonal crystal structure (a = b = 23.710(9) Angstrom, c = 6.703(2) Angstrom, P (3) over bar m1 (No. 164)) is composed of alternate -[B1/3C2/3](infinity )-Sc-C-Sc[B1/3C2/3](infinity)- layers. The boron and carbon atoms -[B1/3C2/ 3](infinity)- form a significantly puckered graphite-like layer in a rather disordered way, The Sc-C-Sc units appear to be rather loosely accommodated between the [B1/3C2/3](infinity) units. Sc-Sc distances show a very close metal-metal contact. In the Sc-C-Sc units carbon atoms are surrounded by si x Sc atoms in the form of a slightly distorted octahedron. (C) 1999 Academi c Press.