Crystal Structure and Magnetic Properties of Na9V14O35:Sodium–Vanadium Bronze -NaxV2O5

The crystal structure of -Na1.3V2O5, a member of NaxV2O5 bronze family, has been determined by single-crystal X-ray study: its actual stoichiometric formula is denoted by Na9V14O35. The monoclinic system P2/c was confirmed with a=15.209(8) ?, b=5.036(5) ? , c=20.786(6) ? , =109.18(3)° with Z=2. The refinements converged to R=0.036 and Rw= 0.037 for 3848 reflections with I>3(I). The structure is of a layer type consisting of V2O5 layers and interlayer Na atoms. The V2O5 layer adopts a novel framework built up with edgesharing VO5 square pyramids for five V atoms (four V4+ and one V4.5+) and vertex-sharing VO4 tetrahedra for two V atoms (V5+). Low-dimensional behavior with a spin gap was observed in the magnetic susceptibility but the structure is dissimilar to any structure type of low-dimensional spin-gap systems. The compound probably presents a new type of spin-gap system.