Ba 3Cu 3(InO 3) 4: A novel quarternary perovskite derivative

Abstract

The novel compound, Ba 3Cu 3(InO 3) 4, is prepared via the reaction between BaCO 3, CuO and In 2O 3 at 1200 K as a dark reddish brown powder. Diffuse reflectivity measurement showed an optical band gap of 1.5 eV while resistivity measurement on a pressed pellet confirmed semiconducting behaviour. Magnetic susceptibility measurements indicated the presence of Cu 2+ cations (measured magnetic moment of 1.90 μ B , a typical value expected for a Cu 2+ cation including spin-orbital coupling) which undergo antiferromagnetic ordering below 15 K. The crystal structure was determined from single-crystal X-ray data and refined to a residual of 0.046 for 513 unique reflections with 27 parameters. Ba 3Cu 3(InO 3) 4 crystallizes in an tetragonal cell (space group, I4 mcm (No. 140)) with four formula units per cell and the lattice constants a = 12.131(2) A ̊ and c = 8.509(2) A ̊ . The structure is an unusual derivative of the perovskite-type framework where the barium atoms in a quarter of the [BaInO 3] − units are replaced by copper atoms. The copper atoms are located in the square planar sites on four of the faces of the [InO 3] 3− unit, thereby yielding a defect NaCl-type oxocuprate indate substructure, 1 ∞ [ mCu 2InO 3 o]. The CuO 4 square planar units are further interconnected to form unprecedented open-link chains which run parallel to the barium occupied channels of the parent perovskite framework.