Synthesis, Crystal Structure and Properties of Ag 4 CuTeO 6

The new quaternary oxide Ag 4 CuTeO 6 has been obtained by solid state reaction starting from stoichiometric amounts of the binary oxides at elevated temperatures and oxygen pressures. Ag 4 CuTeO 6 crystallises in space group C 2/ c with a = 11.3021(8), b = 9.6875(6), c = 5.7082(5) Å, β = 99.301(7)°, V = 616.77(8) Å 3 , Z = 4; the structure refinement was based on 747 independent reflections and resulted in R 1 = 3.26 %, wR 2 = 7.29 %. The crystal structure consists of isolated TeO 6 octahedra which are connected by distorted CuO 4 squares, thus forming one‐dimensional, infinite heteropolyanions, extending along the c axis. According to the approximately fcc packing and a distorted octahedral oxygen environment of all the cations, the structure may be regarded a derivative of the NaCl structure type. Ag 4 CuTeO 6 is paramagnetic between 300 K and 7 K, where it develops antiferromagnetic ordering. An evaluation according to the Curie‐Weiss law yielded a magnetic moment of 1.86 μ B per copper ion. The electronic conductivity shows a maximum at ∼ 75 K, below a temperature characteristic of a semiconductor, above of a metal.