Sc₂B_1.1C_3.2, a New Rare-Earth Boron Carbide with Graphite-like Layers

A Sc-based boron carbide Sc₂B_1.1C_3.2 with a two-dimensional graphite-like framework has been synthesized by a solid state chemical reaction route. Crystals have been grown successfully and the crystal structure could be assigned to represent a new structure type of rare-earth boron carbides. The trigonal crystal structure (a = b = 23.710(9) Å, c = 6.703(2) Å, P3m1 (No. 164)) is composed of alternate -[B_1/3C_2/3]_∞-Sc-C-Sc-[B _1/3C_2/3]_∞-layers. The boron and carbon atoms -[B_1/3C_2/3]_∞- 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 [B_1/3C_2/3]_∞ units. Sc-Sc distances show a very close metal-metal contact. In the Sc-C-Sc units carbon atoms are surrounded by six Sc atoms in the form of a slightly distorted octahedron.