Nanoscale building blocks in a novel lithium arsenotungsten bronze: Synthesis and characterization

• A report on a novel compound Li3AsW7O25 obtained by solid-state reaction.
• Chains and nano-blocks of WO6 octahedra and AsO4 tetrahedra formed a structure like intergrowth tungsten bronzes.
• X-ray diffraction allowed solving the complex arsenotungstate framework.
• Powder neutron diffraction data analysis locates the lithium atoms.
• UV–vis spectrum revealed the band-gap.

We report on a novel compound Li3AsW7O25 obtained by solid-state reaction and characterized by diffraction and spectroscopic methods. The bronze-type compound crystallizes in the orthorhombic space group Pbca with a=724.38(3) pm, b=1008.15(4) pm, c=4906.16(17) pm and Z=8. The structure is built up by chains of WO6 octahedra interconnected by AsO4 tetrahedra and WO6 octahedra forming a polyhedral arrangement as seen in intergrowth tungsten bronzes. The X-ray single crystal structure refinement allows solving the complex arsenotungstate framework. The powder neutron diffraction data analysis locates the lithium atoms. Thermal analysis showed that Li3AsW7O25 is stable up to its melting at 1135(3) K followed by a decomposition at 1182(5) K. The Kubelka–Munk treatment of the UV–vis spectrum revealed a wide band gap in the range of 2.84–3.40 eV depending on the presumed electron transition type.

Crystal structure of Li3AsW7O25 showing different schematic components.Figure optionsDownload as PowerPoint slide