Novel Rare Earth Boron-Rich Solids

A new series of boron-rich solids ReB22C2N (Re: Y, Ho, Er, Tm, Lu) were synthesized by traditional solid-state reaction. The crystal structure of the representative compound YB22C2N was solved by direct method from powder X-ray diffraction (XRD) data and transmission electron microscope (TEM) analysis. The unit cell of the new structure is rhombohedral with space group R-3m (No. 166), lattice constant a=b=5.623(0) ? and c=44.785(3) ? with six formula units in one unit cell. The atoms of boron in the solids, like most of the boron-rich solids, exist with icosahedral and octahedral clusters, and the whole crystal shows a layered structure. The interconnected nine layers of icosahedron and three layers of octahedron in a unit cell build the whole framework of the new phase and rare earth metal atoms reside in voids of the octahedron layers. The neighboring icosahedral layers link through C–B–C chains besides the direct bonding of B–B. Both experimental and structural analysis indicated that the nitrogen atoms in the new phase can be replaced with carbon.