Synthesis and crystal structure of Ba₃Si₄C₂

SiC powder prepared by the Na flux method at 1023 K for 24 h and Ba were used as starting materials for synthesis of tribarium tetrasilicide acetylenide, Ba₃Si₄C₂. Single crystals of the compound were obtained by heating the starting materials with Na at 1123 K for 1 h and by cooling to 573 K at a cooling rate of -5.5 K/h. The single crystal X-ray diffraction peaks were indexed with tetragonal cell dimensions of a = 8.7693(4) and c = 12.3885(6) Å, space group I4/mcm (No.140). Ba₃Si₄C₂ has the Ba₃Ge₄C₂ type structure which can be described as a cluster-replacement derivative of perovskite (CaTiO₃), and contains isolated anion groups of slightly compressed [Si₄]^4- tetrahedra and [C₂]^2- dumbbells. The electrical conductivity measured for a not well-sintered polycrystalline sample was 2.6 × 10^-2-7 × 10^-3 S cm^-1 in the temperature range of 370-600 K and slightly increased with increasing temperature. The Seebeck coefficient showed negative values of around -200 to -300 μV K^-1.