Preparation and crystal structure of a new cesium iron niobium oxide: Cs3Fe0.44Nb5.56O16

Single crystals of a new niobium oxide, Cs3Fe0.44Nb5.56O16 were prepared at 1200°C under an Ar atmosphere. This compound has the orthorhombic space group Pbcm and Z=4. The lattice parameters were a=10.470(3), b=7.514(4) and c=21.312(3) إ, and the final R-factors were R=0.027 and Rw=0.033 for 1085 unique reflections. The crystal structure is a three-dimensional tunnel structure built up by edge- and corner-sharing NbO6 octahedra and (Fe,Nb)O4 tetrahedra and cesium atoms are located in two types of tunnels. The Cs+ ion in the tunnels was ion-exchanged partially with Rb+ ion.