Crystal structure, magnetic properties and conductivity of CuSbTeO_3Cl_2

摘要

CuSbTeO_3Cl_2 has been isolated during an investigation of the system C_u2O:TeCl_4:Sb_2O_3:TeO_2. The new compound is light yellow and crystallises in the monoclinic system, space group C2/m, a=20.333(5) A, b=4.0667(9) A, c=10.778(2) A, Z = 6. The structure is layered and is built up from corner and edge sharing [(Sb,Te)O_4E] trigonal bipyramids that have the lone pair (E) directed towards one of the equatorial positions, those groups build up [(Sb,Te)_2O_3E_2~+]_n layers. The copper and the chlorine atoms are located in between those layers. There are two different Cu positions. The [Cu1Cl_4] group is a slightly distorted tetrahedron and these tetrahedra make up chains by corner sharing. The electron density for the half occupied Cu2 atom is spread out in the structure like a worm that run along the b-axis in the space in between two chains of [Cu1Cl_4] tetrahedrons. Analysis of the diamagnetic response in magnetic susceptibility measurements is in perfect agreement with a Cu+ valence. Conductivity measurements in the temperature range 355–590 K gives an activation energy of 0.55 eV. The delocalised Cu2 position in the structure suggests that the compound is a Cu~+ ionic conductor along the b-axis.