Preparation, Structure Refinement, and Properties of Some Compounds with Dy 2Fe 2Si 2C- and LaMn 11C 2- x-Type Structure

Abstract

The new compounds Tm 2Fe 2Si 2C and Lu 2Fe 2Si 2C were prepared by are-melting cold-pressed pellets of the elemental components. They crystallize with the monoclinic Dy 2Fe 2Si 2C-type structure. The crystal structure of Tm 2Fe 2Si 2C was refined from single-crystal X-ray data: C2/ m, a = 1049.7(3) pm, b = 388.2(1) pm, c = 664.6(2) pm, β = 128.96(2)°, R = 0.020 for 296 structure factors, and 21 variable parameters. The structure may be considered as consisting of two-dimensionally infinite polyanionic layers of [Fe 2Si 2C 6-] n separated by the rare-earth cations. The hydrolysis of Er 2Fe 2Si 2C with diluted hydrochloric acid yields mainly methane besides about 20 wt% of C 2 and C 3 hydrocarbons. Tm 2Fe 2Si 2C orders antiferromagnetically at T N = 2.7(2) K. The magnetization behavior for this compound suggests metamagnetism. Lu 2Fe 2Si 2C is Pauli paramagnetic. Electrical conductivity measurements of polycrystalline samples of Tm 2Fe 2Si 2C and Lu 2Fe 2Si 2C indicate metallic conductivity. ThFe 10SiC 2- x has a tetragonal LaMn 11C 2- x -type structure with the lattice constants a = 1005.3(2) pm and c = 651.6(2) pm.