6533b835fe1ef96bd129f40f

RESEARCH PRODUCT

Local atomic and electronic structure of tungsten ions in AWO4 crystals of scheelite and wolframite types

subject

description

Abstract X-ray absorption spectroscopy was used to study the local atomic and electronic structure of tungsten ions in polycrystalline scheelite CaWO4 and wolframite-type ZnWO4 and NiWO4. The W L1- and L3-edges X-ray absorption near edge structure (XANES) signals suggest tetrahedral coordination of tungsten ions in CaWO4 and strongly distorted octahedral coordination in ZnWO4 and NiWO4. Accurate analysis of the W L3-edge extended X-ray absorption fine structure (EXAFS) signals by the regularization procedure was performed to reconstruct the radial distribution functions within the first coordination shell around tungsten atoms in AWO4 crystals and polycrystalline WO3, which was utilized for comparison. For the local environment around tungsten atoms in CaWO4, we found very good agreement with known crystallographic data, suggesting the presence of four oxygen atoms at ∼1.79 A . The results obtained for ZnWO4 and NiWO4 show similarity of their local atomic structures: the oxygen atoms forming [WO6] octahedra can be divided into two groups — four atoms at 1.84±0.01 A and two atoms at 2.13±0.01 A .