A novel boron-rich scandiurn borocarbide; Sc4.5-xB57-y+zC3.5-z(x=0.27, y=1.1, z=0.2)

摘要

A novel ternary boron-rich scandium borocarbide Sc4.5-xB57-y+zC3.5-z (x = 0.27, y = 1.1, z = 0.2) was found. Single crystals were obtained by the floating zone method by adding a small amount of Si. Single-crystal structure analysis revealed that the compound has an orthorhombic structure with lattice constants of a = 1.73040(6), b = 1.60738(6) and c = 1.44829(6) nm and space group Pbam (No. 55). The crystal composition ScB13.3C0.78Si0.008 calculated from the structure analysis agreed with the measured composition of ScB12.9C0.72Si0.004. The orthorhombic crystal structure is a new structure type of boron-rich borides and there are six structurally independent B-12 icosahedra I1-I6, one B-8/B-9 polyhedron and nine bridging sites all which interconnect each other to form a three-dimensional boron framework. The main structural feature of the boron framework structure can be understood as a layer structure where two kinds of boron icosahedron network layer L1 and L2 stack each other along the c-axis. There are seven structurally independent Sc sites in the open spaces between the boron icosahedron network layers. (C) 2002 Elsevier Science (USA). [References: 13]